THE UNIVERSITY OF ILLINOIS LIBRARY mvm geology The person charging this material is re- sponsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. To renew call Telephone Center, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN L161— 0-1096 Digitized by the Internet Archive in 2016 with funding from University of Illinois Urbana-Champaign Alternates https://archive.org/details/studyofforestcon1519holm r: i I i I i I i I * I i I i I i I i I i t X I $ I l I i I i I * I i I l I $ I i I i I f l; Mississippi State Geological Survey ALBERT F. CRIDER, DIRECTOR. 1 i BULLETIN NO. 1 i I t I i Cement and Portland Cement Materials of Mississippi By ALBERT F. CRIDER NASHVILLE BRANDON PRINTING COMPANY 1907 'V) •H* >♦♦♦ >W< >444' >444—444' s s I x x I * I i I I i I * I i I i I i I i i N.H.U STATE GEOLOGICAL COMMISSION. His Excellency, James K. Vardaman Governor Dunbar Rowland Director of Archives and History A. A. Kincannon Chancellor of the State University j c Hardy President Agricultural and Mechanical College Joe N. Powers State Superintendent of Education GEOLOGICAL CORPS. Albert F. Crider Dr. William N. Logan Dr. Calvin S. Brown. Director Assistant Geologist Assistant Geologist o * < LETTER OF TRANSMITTAL. Jackson, Miss., July 20, 1907. To Governor James K. Var daman, Chairman , and Members of the Geological Commission: Gentlemen — I submit herewith my report on Cement and Port- land Cement Materials of Mississippi. Very respectfully, Albert F. Crider, Director. i O F 1 TABLE OF CONTENTS. PAGE Letter of transmittal 3 List of tables 7 List of illustrations 9 Acknowledgments 10 Introduction 11 Early history of the Portland cement industry 12 Present condition of the industry in the United States 12 Cement industry in the South 15 Classification of cements 16 Simple cements 16 Hydrate cements 16 Carbonate cements 16 Complex cements 17 Natural cement 17 Puzzolan cement 18 Portland cement 19 Raw materials of Portland cement 21 Argillaceous limestone 21 Hard pure limestone 22 Chalk 23 Fresh-water marl 24 Oyster shells 25 Alkali waste 25 Slag.: 26 Clay 27 Shale 27 Slate 28 Methods of Portland cement manufacture 28 Preparing and grinding the raw materials 28 Dry process 29 Wet process 31 Preparing slag for cement 31 CONTENTS. 5 Methods of Portland Cement Manufacture— Continued. Burning Fuels Coal Oil Natural gas Producer gas Grinding the clinker Retarder for quick-setting cements Portland cement materials of Mississippi General geology Devonian Carboniferous Cretaceous Tuscaloosa clays Selma chalk Thickness Distribution Corinth and vicinity Booneville and vicinity Tupelo and vicinity Okolona and vicinity Starkville and vicinity Macon and vicinity Available clays in and adjacent to the Selma area.. Residual Selma clays Porter’s Creek clay Jackson formation Distribution Yazoo City Jackson Vicksburg formation Distribution Vicksburg Byram Plain Brandon Bay Spring PAGE 32 32 32 34 34 34 35 36 36 36 37 38 40 40 40 42 43 43 45 46 48 49 50 54 54 55 57 57 57 58 59 60 60 63 63 64 65 6 CONTENTS. PAGE Advantageous locations for cement plants in Mississippi 68 Tishomingo County 68 Starkville and West Point 68 Columbus 69 Jackson and vicinity 69 Vicksburg 70 Index 71 Map 00 LIST OF TABLES, PAGE 1. Production of Portland cement in the United States in 1903, 1904 and 1905, by States 14 2. Analyses of natural cement rock used in American and European plants 18 3. Analyses of American Portland cements 20 4. Analyses of argillaceous hard limestones, “cement rock,” used in American cement plants 22 5. Analyses of chalk used in American cement plants 24 6. Analyses of marls used in American cement plants 25 7. Analysis of oyster shells from Biloxi 25 8. Analyses of alkali waste 26 9. Analysis of slag used in German Portland cement plants .... 26 10. Analyses of kiln coals 33 11. Analyses of Mississippi lignites '. . 35 12. Analyses of Devonian limestone, Tishomingo County 38 13. Analyses of Carboniferous limestones and shale, Tishomingo County 39 14. Analyses of Tuscaloosa clays of Mississippi 40 15. Analysis of Selma limestone from Corinth 44 16. Analysis of Selma limestone 2J miles south of Tupelo 47 17. Analysis of Selma limestone 1 mile west of Tupelo 47 18. Analyses of Selma limestone from Okolona 49 19. Analyses of Selma limestone from Oktibbeha County 50 20. Analyses of Selma limestone from Oktibbeha County 50 21. Analyses of Selma limestone from Macon 51 22. Analysis of Selma limestone from 3 miles north of Macon. ... 51 23. Analysis of Selma limestone from Prairie Rock 52 24. Analysis of Selma limestone from Crawford 52 25. Analysis of clay from Crawford 53 26. Analysis of Selma limestone from 5 miles east of Shuqualak. 53 27. Analyses of Selma limestone from Kemper County 53 28. Analyses of Selma limestone used at the Alabama Portland cement plant, Demopolis 54 8 LIST OF TABLES. PAGE 29. Analysis of residual clay from Uniontown, Ala 55 30. Analyses of residual Selma clays from Mississippi 55 31. Analysis of residual Porter’s Creek clay from 1 mile west of Starkville 56 32. Analyses of Porter’s Creek clay 56 33. Analysis of Porter’s Creek clay from Scooba 56 34. Analysis of Jackson marl-clay from Yazoo City 58 34a. Analyses of Jackson marl and clay, 1 mile south of Jackson . . 58 35. Analyses of Vicksburg limestone and marls from Vicksburg. . 61 36. Analyses of Vicksburg limestone and marls from Vicksburg. . 62 37. Composition of actual mixes used in American cement plants . 62 38. Analyses of Vicksburg limestone and marl from Byram 63 39. Analyses of Vicksburg limestone and marls from near Plain. . 64 40. Analyses of Vicksburg limestone from Robinson quarry, 4 miles southeast of Brandon 65 41. Analyses of Vicksburg limestone from near Nancy, Clarke County 66 42. Analyses of Vicksburg limestone from Red Hill, Wayne County 67 LIST OF ILLUSTRATIONS. Plate page I. Selma chalk bluff, Macon 50 II. Lafayette and residual clay overlying Selma chalk. Macon . . 52 III. Bluff at Vicksburg showing Vicksburg limestone 60 IV. Ledge of Vicksburg limestone, Clinton 62 V. Vicksburg limestone on Pearl River, Byram 64 VI. Vicksburg limestone, Robinson quarry, near Rankin 66 ACKNOWLEDGMENTS. In the preparation of this report the author is under many obliga- tions to Drs. William N. Logan and Calvin S. Brown, of the State Survey, for collecting samples of limestones and clays, and for other valuable assistance. The credit of the chemical analyses, unless otherwise stated in the report, belongs to Dr. W. F. Hand, State Chemist, Agricultural Col- lege. The author is indebted to Mr. D. L. Mitchell, of Biloxi, Miss., for reading the manuscript and offering valuable suggestions. In the discussion of the technology and manufacture of cements the various works of Mr. E. C. Eckel, of the United States Geological Survey, have been freely used. CEMENT AND PORTLAND CEMENT MATERIALS OF MISSISSIPPI. By Albert F. Crider. INTRODUCTION. The growth oi almost every line of the mining industry in America in the last decade has been most phenomenal. The mineral produc- tion of the United States for 1905, the latest year for which complete official returns are available, was $1,623,877,120. Of this amount $921,024,019 was contributed by the non-metallics, and $702,453,101 by the metallics. The value of Portland cement products is surpassed only by iron, gold, copper, coal, oil and stone. In its importance to the advance- ment of the present civilization it is surpassed only by iron, coal and oil. Its per cent of increase in production and consumption since 1890 is greater than any mineral mined in the United States. Until 1905 the amount of Portland cement imported into the United States was greater than the amount exported. In 1891 the amount of production was 454,813 barrels, and the amount imported was 2,998,313 barrels. In 1905 the amount imported had been reduced to 896,845 barrels, and the amount exported was 897,686 barrels. Some sections of the United States have not been able to secure all the cement they could use, and there is an increasing demand for our cement in foreign countries, especially in the Central and South American States, and the West Indies. But before we need to exploit fields outside of the United States for our cement we must create a surplus over and above the amount consumed at home. But with the increase in production due to the erection of new plants and the enlargement of the old ones comes new demands for cement as a structural material from every section of the country. No section of the United States is advancing quite so rapidly as the South. The advance in the manufacture of cements has not kept 12 CEMENT MATERIALS. pace with the progress in other lines of industry, and for this reason the South offers practically an open field to the cement manufacturer. And in no section of the South is this more evident than in Mississippi where, at present, there is not a single cement plant. The object of this report is to point out the geographical distribution, the available amount and the quality of cement materials, and call attention to the economic advantages offered for the erection of cement plants within the State. EARLY HISTORY OF THE PORTLAND CEMENT INDUSTRY. Portland cement was first made in 1824 by Joseph Aspdin, a brick- layer in Leeds, England. The name “Portland” was chosen because of the resemblance of the cement to the oolitic limestone of Portland, England. The limestone is extensively used in England as a road metal and building stone. The first cement was made by taking a specific quantity of road scrapings from roads repaired with the oolitic limestone and reduced to a powder and calcined. The calcined material was then combined with a specific quantity of argillaceous earth or clay, mixed with water, and the mixture placed in a pan and heated until all the water was evaporated. After this the mixture was broken into small lumps and calcined in a furnace similar to a lime kiln till the carbonic acid was entirely expelled. It was then cooled and reduced to a powder which had the power of setting when mixed with water. Aspdin ’s original patent did not specify the percentages of lime- stone and clay in the mixture, and he also omitted to state that the mixture should be burned until incipient vitrification is attained. In the absence of machinery for grinding the hard limestone, he was forced to calcine it before it was mixed with the clay. From this crude beginning has developed one of the greatest industries of building material of modem times. PRESENT CONDITION OF THE INDUSTRY IN THE UNITED STATES. The Portland cement industry has had a more marvelous growth than any other large industry of this era. It came at a most oppor- tune time in the development of the country. It has prolonged the PRESENT CONDITION OF INDUSTRY. 13 life of lumber and supplemented iron and steel. It has become one of the leading and most substantial products for general construction work where strength, durability and economy are required. It is used alone, or as a reinforcement in the construction of bridges, busi- ness and dwelling houses, aqueducts, sewers, pavements, large founda- tion walls and dikes such as the Galveston wall, docks, wharves and levee work; besides in many minor ways, such as in making fence posts, telegraph poles, railway ties, monuments, and in various other lines of construction work. The output of Portland cement in the United States in 1890 was only 335,500 barrels. In 1900 it had reached 8,482,020. The most rapid growth of the industry was between 1900 and 1905. Prelimi- nary figures in 1906, announced by the United States Geological Survey, show that 46,463,424 barrels were produced, valued at $52,446,186. This is even a greater increase in output and in value than that of the previous year. The following table shows the amount and value of Portland cement produced in the different States where this article was man- ufactured in 1903, 1904 and 1905: TABLE 1. PRODUCTION OF PORTLAND CEMENT IN THE UNITED STATES IN 1903, 1904 AND 1905, BY STATES. t [Barrels.] 14 CEMENT MATERIALS. If a s ^ ‘o' CO b- r-, 04 00 o lO CO 04 00 04 t" O 05 lO -h i-4 04 '-I' TJ 4 * ^4 CO O- rH © 04 O Nf iq o O r>T N ^ 00 CO H O O S O IQ 00 IQ Cl N 04 ^ O 0- O CO H 04* 04* r-4 rH n 04 N H N t» 00 If h H N 00 04 O N if O if 04 X X 04 r- i CO os t'- O CO 05 rH CO* 00* 1*4 CO Tj4 CO X ^4 O OC 1C 04 ■f h « rH t>. 1-H h o e 05* 04* rf "S' CO CO ^ 04 1-1 C- t'- *-o X 04 05 04 »—t X 05 iJ4 ^ C5 H H O! O) if iq 04 © 05* 04* O CO* 05 CO rl 05 CO 05 K 3 ^ 404 hc 004 C 0 HNN s 1 a s 04 IQ lO CO CO LO 1—4 CO lO O- 1-H C- o © O O) H iq rq cq rJ4* t>-‘ lO If 00 05 CO 04 O N 04 O CO X »q rH cq f-* tC 05* IONH 04 O O o If4 Tj4 o O 04 X X © rH © 05 c- X cq cq cq X "tf* TJ4* tJ 4* rH x* IT) CO tJ4 CO C5 O cq i-4 os © 05 cq 04* i—4* 04* 04* 1-4* X -H © 05 CO X © X 1*4 rH rH 1-4 cq cq 05 io cq K5 IQ CO* 04 05 If X 04 05 O 04 lO 05 x cq cq i> 1—4^ 04* rH* 05* •I 111 3 .co g CD S V? 2 .2 •§ # 3 £ o -S -3 S % * •c S ° g^>4 52 £ £ a £ > /S C 53 G 0 _4) o G G ° '& _ to .3 .2 G > .SgC bO eg co tMineral Resources of the United States, 1905, U. S. Geological Survey, p. 926. *Shut down. (а) Total amount combined and given with Virginia. (б) Total amount combined and given with Kansas. ( c ) Total amount combined and given with Colorado. INDUSTRY IN THE SOUTH. 15 New plants are reported to be in process of construction or com- pleted in the following States: Iowa, 2 plants. Oregon, 1 plant. Wisconsin, 2 plants. Tennessee, 1 plant. Alabama, 2 plants. Georgia, 1 plant. The total number of Portland cement plants in the United States at the present time approaches the one hundred mark. CEMENT INDUSTRY IN THE SOUTH. Of the whole number of plants in the United States there are but 8 in the South producing cement, and about 4 new plants under construction. According to the latest official report the South pro- duces less than 4 per cent of the total amount of Portland cement manufactured in the United States. This, added to the fact that the South is growing more rapidly than any other section of the country, gives a promising outlook for the development of the cement industry. There should be a large number of plants located in various sections of the South to equalize the output in the United States; at least a sufficient number to supply the local demands. At present Mississippi is dependent upon the cement plants of Alabama and other States for cement. There is a wide field in Missis- sippi for the development of this important industry. With an abundance of excellent raw materials favorably located, as at Vicks- burg where coal is cheap and with railway and water transportation, there is no reason why Mississippi should not enter the field as a cement-producing State and supply a large amount of the increasing demand in the middle South. The erection of a plant in this unde- veloped territory would be a paying investment, and would ultimately cheapen the product to the consumers. It has been reported by government authorities that the construc- tion of some of the locks of the Panama Canal will require about 92,000 carloads of cement. This amount equals about one-fourth of the output of all the cement plants in the United States for 1905. There is an ever increasing demand for cement in the United States as shown 16 CEMENT MATERIALS. by the fact that during 1905 over 35,000,000 barrels were used, besides 896,845 barrels shipped in from other countries. While the Panama Canal trade may appeal to some of the factories of the United States, there is not a sufficient number of plants in the South at the present time to supply the increasing local demand. CLASSIFICATION OF CEMENTS.* Cements may be classified under two general heads, Simple cements and Complex cements. SIMPLE CEMENTS. Simple cements are those in which the setting properties are similar to the original raw material. Under this class come (1) hydrate cements and (2) carbonate cements. (1) Hydrate Cements . — Hydrate cements include those cements in which the water of combination from certain rocks has been driven off by heat not exceeding a temperature of 400° Fahrenheit, and which upon the reabsorption of water produce an artificial rock sim- ilar to the original. The hydrate cements are “Plaster of Paris,” “Keene’s cement,” “Parian cement” and “Cement plaster.” They are all manufactured from gypsum and differ from each other only in the addition of rela- tively small amounts of clay, limestone, sand and other materials; or by slight variations in the methods of manufacture. (2) Carbonate Cements . — Carbonate cements are formed from lime- stone by dissociating and driving off the carbon dioxide (C0 2 ) and the water of combination by the application of heat at a temperature between 1,382° F. and 1,652° F., leaving behind “quicklime” or unslaked lime (CaO). “Quicklime” on being treated with water expands and gives off heat, forming the hydrated calcium oxide or slaked lime (Ca H 2 0). The cementing qualities are imparted to the hydrated calcium oxide on the reabsorption of carbon dioxide from the air, forming the original calcium carbonate or limestone. Only the outer portions of the walls are thoroughly recarbonated, since the reabsorption of the carbon dioxide can only take place where the material is exposed *In the treatment of this subject the writer has followed E. C. Eckel in Limes, Cements and Plasters. COMPLEX CEMENTS. 17 to the air. The products of carbonate cements are calcium and magnesian limes. It requires a higher degree of temperature to dis- sociate a relatively pure limestone than one containing a high per cent of magnesium, and the resulting quicklime slakes more readily and has a quicker set. The magnesian limes have a slower set, but attain a higher degree of strength. COMPLEX CEMENTS. In the manufacture or in the use of complex cements certain chemical changes take place forming new compounds which impart the setting properties to the cement. In this class come natural cements, Puzzolan cements, hydraulic limes, and Portland cement. In all of these the cementing quality is imparted by calcium oxide in the presence of silica and alumina approaching a tri-calcic silicate. There are, however, certain natural or added impurities in the lime- stone and clays or shales to form various lime silicates and silico- aluminates. The most common impurities formed" in limestones, clays and shales are iron, magnesia, alkalies and sulphur. Calcium sulphate is added to some cements to retard the set. The impurities act as a flux upon the body of the materials and greatly reduce the temperature of incipient fusion. Natural Cement. Natural cement is produced by burning an impure limestone con- taining from 15 to 40 per cent of silica, alumina and iron oxide. In addition to these ingredients it usually contains a small per cent of alkalies, sulphur trioxide and water. The temperature required for burning hydraulic limestone is about the same as that obtained in burning lime, or between 900° to 1,300° F. All the combined water and most of the carbon dioxide are driven off and the lime and magnesia combine with the iron oxide, silica and alumina. The fluxing properties, such as soda and potassium, aid in decomposing these ingredients. The burned product shows little or no free lime. The burned mass or clinker is ground to a fine powder, which has the power of setting when placed under water. Natural cements differ from common lime in possessing hydraulic properties and refusing to slake before grinding. They differ from 18 CEMENT MATERIALS. Portland cements in not being a mechanical mixture of raw materials possessing definite chemical constituents. They have a specific gravity which ranges from 2.7 to 2.9; while Portland cement has a specific gravity from 3.0 to 3.2. Natural cements are burned at a lower temperature, have a quicker set, and a much lower ultimate strength than the true Portland cements. Magnesia is found in comparatively large quantities in the raw materials used in the natural cement plants in the United States. It does not, however, possess any hydraulic properties within itself, and could be easily exchanged for lime without affecting the quality of the cement. The hydraulic properties are imparted to the lime- stone by the clayey materials, the silica, and the iron oxide. The following are analyses of natural cement rock now in use in American and European natural cement plants: TABLE 2. ANALYSES OF NATURAL CEMENT ROCK USED IN AMERICAN AND EUROPEAN PLANTS.* Si02 ! ai 2 o 3 Fe20 3 CaO MgO S0 3 | co 2 H*0 S Rosendale, N. Y 10.90 3.40 2.28 29.57 14.04 0.61 37.90 n.d. n.d. Milton, N. D 14.00 6.70 37.60 n.d. 0.58 n.d. n.d. 1.45 Defiance, Ohio 42.00 7.00 7.10 9.91 5.81 n.d. 14.18 14.00 Copley, Pa 18.34 7 49 37.60 1.38 n.d. 31.06 3.94 Balcony Falls, Va 17.38 7.80 34.23 9.51 n.d. 30.40 n.d. n.d. Milwaukee, Wis 17.00 4.25 1.25 24.64 11.90 n.d. 32.46 n.d. Mankato, Minn.t 16.00 5.85 2.73 22.40 14.99 n.d. 34.11 n.d. n.d. Fort Scott, Kan 17.26 2.05 5.45 34.45 5.28 n.d. 32.87 n.d. n.d. Utica, 111 17.01 3.35 2.39 32.85 8.45 1.81 34 .1 2 Louisville, Ky 9.80 2.03 1.40 29.40 16.70 n.d. 41.49! n.d. n.d. Belgium 15.75 3.95 1.00 43.10 0.49 0.50 35.21 n.d. England J 18.00 6.60 3.70 39.64 0.10 n.d. 29.46 1.30 n.d. Puzzolan Cement. The process of making Puzzolan cement was known to the ancients, and was named from its use at Puzzolano, Italy. It is produced from an un calcined mixture of slaked lime and a silico-aluminous material, such as volcanic ash, or blast-furnace slag. The process is simply a mechanical mixture of the two materials. ♦Cements, Limes and Plasters, E. C. Eckel, 1905, pp. 204-217. t Alkalies 0.76. PORTLAND CEMENT. 19 The ingredients are thoroughly mixed and ground to a fine powder, which will set under water. The per cent of lime and slag used in the mixture is about 35 parts of slaked lime to 100 parts of slag. Puzzolan cements are of a lighter color, have a lower specific gravity and a much lower set than Portland cements. Portland Cement. There are at present many different kinds of cements manufactured and sold as Portland cements. Some of these are made by burning a natural magnesian, argillaceous limestone and grinding it to a powder. According to the best authorities, however, on the manu- facture of cements, these would be excluded from the list of true Portlands. The following definition,* perhaps, comes near fulfill- ing all the conditions of the best Portland cements: “By the term Portland cement, is to be understood the product obtained by finely pulverizing clinker produced by burning to semi- fusion an intimate artificial mixture of finely ground calcareous and argillaceous materials, this mixture consisting approximately of three parts of lime carbonate (or an equivalent amount of lime oxide) to one part of silica, alumina, and iron oxide. The ratio of lime (CaO) in the cement to the silica, alumina, and iron oxide together shall not be less than 1.6 to 1, or more than 2.3 to 1.” Prom the above definition it is evident that all cements produced by burning argillaceous limestones without grinding the mixture before burning are excluded from the list of true Portland cements. To bum the materials to a semi-fused mass requires a temperature of something like 3,000° F. This can only be obtained in kilns made especially for this purpose. The chemical changes which take place in the kiln are, first, the expulsion of the mechanically held water, which is driven off at a temperature of 212° F. ; second, the dissociation of the lime carbonate at about 1,300° F., setting free carbon dioxide and sulphur trioxide third, at about 2,600° F. and above, clinkering takes place, the silica and alumina are decomposed, and the lime oxide, silica, alumina and iron oxide combine, forming silicates, aluminates and ferrites of lime in definite proportions. ♦Cements, Limes and Plasters, E. C. Eckel, p. 297. 20 CEMENT MATERIALS. The semi-fused mass when finely pulverized will set under water. The specific gravity of Portland cement is from 3.0 to 3.2. The chemical composition of Portland cement varies within cer- tain limits. The first Portlands manufactured in England were low in lime oxide. Some of the earliest brands ran as low as 50 per cent in lime. The best brands now manufactured in the United States have a general average of about 62 per cent of lime oxide. In an investigation of 81 analyses of American brands, the maximum amount of lime oxide was about 65.44 per cent, and the minimum amount 58.07 per cent. The amount of silica varied from about 19 per cent to 24 per cent, with a general average of about 21.75 per cent. The amount of alumina and iron oxide together varied from 6 per cent to 13.5 per cent with a general average of about 10.5 per cent. The amount of magnesia varied from a trace to 3.5 per cent. The greatest amount of alkalies was 2.25 per cent. The amount of sulphur trioxide varied from a fraction of 1 per cent to 2.786 per cent. TABLE 3. ANALYSES OF AMERICAN PORTLAND CEMENTS.* 1 2 3 4 5 6 7 8 9 10 1 11 12 Silica (SiOj) 20.14 22.48 20.80 22.04 21.20 19.92 21.96 22.00l22.00 22.50 20.25 8 i Alumina (AI 2 O 3 ) 7.51 6.52 7.39 6.45 6.05 9.83 9.29' l Q 74., [ 7.74 8.35' l 19 A A. f 7.50 Iron oxide (Fe 2 C> 3 ) . . . 3.33 4.46 2.61 3.41 3.33 I 2.63 i 2.67 \ 4.61 4.25 / lO \ 2.40 Lime oxide (CaO) .... 62.71 62.93 64.00 60.92 58.07 60.32 60.52 62.34 59.50 62.35 63.60 62 00 Magmpsia (MgO) 2.34 1.48 n.d. 3.53 2.80 3.12 3.43 2.54 0.90 1.03 2.50 Alkalies (K 2 O Na20) 2.20 1.20 Sulphur trioxide (SO 3 ) 1.64 1.30 n.d.i 2.73 1.13 1.49 1.40 0.80 1.75 0.41 1.50 1. Edison Portland Cement Co., New Jersey. 2. Catskill Portland Cement Co., New York. 3. Empire Portland Cement Co., New York. 4. Empire Portland Cement Co., New York. 5. Buckeye Portland Cement Co., Ohio. 6. American Portland Cement Co., Pennsylvania. 7. Atlas Portland Cement Co., Pennsylvania. 8. Lehigh Portland Cement Co., Pennsylvania. 9. Western Portland Cement Co., South Dakota. 10. Texas Portland Cement Co., Texas. 11. Alabama Portland Cement Co., Alabama. 12. Michigan Portland Cement Co., Michigan. ♦Cements, Limes and Plasters, E. C. Eckel, 1905, pp. 577 to 579. RAW MATERIALS. 21 RAW MATERIALS OF PORTLAND CEMENT. The principal constituents which enter into the manufacture of Portland cement are lime, silica, alumina and iron oxide. These materials are found widespread in nature and occur in various com- binations, especially in sedimentary rocks. It is from these rocks the necessary constituents are found for making Portland and natural cements. Lime is found in argillaceous limestones, hard pure lime- stones, chalks, marls, oyster shells, alkali waste and blast-furnace slags. Silica, alumina and iron oxide are found principally in clays, shales and slates, although they all frequently occur in greater or less quan- tities in limestones. A limestone may vary in composition from pure calcium carbonate (CaC0 3 ), calcite, to a rock containing an increasing amount of clay or sand, until the name limestone is no longer appli- cable. There is a regular gradation from a pure limestone to a pure clay or sand. It is possible, therefore, to find a rock in nature, in small quantities at least, which would contain the exact proportions of lime, silica, alumina and iron oxide for a Portland cement. It is hardly probable, however, that such a rock would occur in large quantities. ARGILLACEOUS LIMESTONE. A limestone containing a relatively large amount of clayey material in chemical combination with lime is called an argillaceous limestone. It has been formed at the bottom of an open or inland sea by cal- careous remains of small invertebrate organisms, in the presence of sediments carried by streams from the shore. The purest limestones are formed at too great a distance from the shore to receive any accumulation of sediments. Owing to the constant agitation of the water near the shore sandstones and clays have but little or no organic remains. The argillaceous limestones, therefore, represent an inter- mediate stage between the pure limestones and the non-calcareous near-shore deposits. There is no definite rule for determining when a limestone shall be called “argillaceous.” The argillaceous limestone in the “Lehigh district” of Pennsylvania and New Jersey has been called “cement rock,” because it has been the most important source of cement in this country. Until as late as 1903 two-thirds of the Portland cement 22 CEMENT MATERIALS. manufactured in the United States was made from the “cement rock” of the Lehigh district, mixed with pure limestone. This district is still producing 38 per cent of the Portland cement of the United States. The quality and composition of some of the argillaceous limestones now used by American cement plants are here given: TABLE 4. ANALYSES OF ARGILLACEOUS HARD LIMESTONES, “CEMENT ROCK,” LEHIGH DISTRICT.* Silica (SiOj) Altunina (AljOs) Iron oxide (FeiOs) Lime carbonate (CaCOj) Magnesium carbonate (MgCOs) . Carbon dioxide (CO 2 ) 18.30 15.97 17.32 19.62 16.77 15.73 19.06 6. U 7.53\ J 4.44 1.85 2.24/ 9 11 5 68 6 50 792 \ 1.14 36.38 34.34 38.59 39.08 41.37 39.62 38.77 2.13 3.93 2.05 2.35 n.d. 1.81 2.02 28.96 32.80 32.55 33.25 n.d. 33.08 32.66 ANALYSES OF ARGILLACEOUS LIMESTONES FROM WESTERN UNITED STATES.t Silica (SiC> 2 ) 21.02 6.80 20.06 7.12 14. 20 Alumina (AI2O3) 8.00 3.00 10.07 2.36 5. 21 Iron oxide (Fe20s) 3.39 1.16 1 . 73 Lime carbonate (CaCO») 62.08 89.80 63.40 • 87.70 75. 10 Magnesium carbonate (MgCOj) . . . 3.80 0.76 1.54 0.84 1 . 10 It will be seen by a study of the above analyses that in order to bring the argillaceous limestones to the proper composition of Port- land cement (75 to 77 per cent of lime carbonate) they require the addition of a purer limestone. HARD PURE LIMESTONE. Pure limestone has the composition of calcite (CaCo 3 ), correspond- ing to the composition, calcium oxide, 56 per cent; carbon dioxide, 44 per cent. The theoretically pure limestone is rarely met with in nature in large quantities. The most common impurities found in limestones are magnesia, silica, alumina, iron, alkalies and a few minor materials. Magnesia may be carried in solution and introduced into the limestone when it is being formed, or subsequently forming a mag- *Cements, Limes and Plasters, E. C. Eckel, 1905, p. 329. fBulletin 243 U. S. Geological Survey, 1905, p. 32. LIMESTONE AND CHALK. 23 nesian limestone. The calcium carbonate is replaced by the magnesium carbonate. Limestones in which the calcium carbonate and the mag- nesium carbonate are united in equal molecular proportions are called dolomites, having a formula CaC0 3 , MgC0 3 , and are composed of 54.35 per cent calcium carbonate, and 45.65 per cent magnesium carbonate. Magnesia in Portland cement is an inert material and limestones containing more than 5 or 6 per cent of it should be avoided. Where the impurities in the limestones are chiefly clayey materials, silica, alumina and iron oxide, the chemical composition of the raw material is of the greatest importance to the cement manufacturer, and should be carefully studied. Where the silica is present in lime- stones in the form of free sand or chert nodules it will not easily enter into combination with the calcium carbonate, and is, therefore, largely an inert material. If, however, silica and alumina are com- bined in the form of clay, shale or slate they readily combine with the calcium carbonate under the action of heat. A cement manufacturer having a limestone with a high per cent of calcium carbonate must select a clay with a high silica-alumina ratio. If, however, he has a limestone with a low per cent of calcium carbonate great care must be used in selecting a clay with a low silica-alumina ratio. “For this reason it may be taken as a safe rule that when a lime- stone carries less than 90 per cent of lime carbonate it should give a value between 2.25 and 3.00 for the ratio Xhol+^Oa - These are comfortable limits, and will give the manufacturer considerable latitude in his choice of a clay to mix with it.”* CHALK. Chalk is a white limestone so soft that it can be easily scratched with the finger nail. Where pure it is composed of fine sediment of calcium carbonate derived chiefly from shells of foraminifera. Like other forms of calcareous deposits it varies from a rather pure calcium carbonate to a chalky limestone containing silica, alumina, magnesia, iron and other impurities, requiring little additional material to make ♦Cements, Limes and Plasters, E. C. Eckel, 1906, p. 316. 24 CEMENT MATERIALS. it suitable for Portland cement manufacture. The range in com- position of chalky limestones used in American cement plants is here given : TABLE 5. ANALYSES OF CHALK USED IN AMERICAN CEMENT PLANTS. Silica (SiO*) .... 12.50 9.88 5.33 12.13 2.22 Alumina (AljO*) '"J 2.76 6.20 3.03 f 4.17 .92 Iron oxide (FejOj) \ 3.28 .18 Lime (CaO) 45.20 43.19 50.53 42.04 54.08 Magnesia (MgO) 0.50 0.52 0.55 0.44 0.10 Carbon dioxide (CO 2 ) 36.06 34.49 50.30 33.51\ 42.50 Water 1.36 5.72 n.d. n.d.J The most extensive calcareous formation in Mississippi is the Selma chalk or “rotten limestone” which is more than 900 feet thick in Lowndes, Noxubee, Oktibbeha, Clay, Monroe and Chickasaw counties, and thins to about 300 feet in Alcorn County. Under the discussion of the. Selma chalk are numerous analyses, some of which are inferior to and some better than the ones given above. FRESH-WATER MARL. Marl, such as is used in cement manufacture, is a chemical deposit of almost pure carbonate of lime which has been deposited in inland seas and lakes by streams or springs carrying lime carbonate in solu- tion. Marls differ from hard limestones in that they are masses of granular, incoherent deposits containing land shells and shell frag- ments. Workable deposits of marl are chiefly confined to that part of the United States which was formerly . covered by glacial deposits. Most of the lakes of northern United States and Canada are due to the damming of streams, and to the uneven distribution of the glacial deposits. The streams of that region carry a large per cent of lime carbonate in solution and deposit it on the sides and bottoms of the enclosed lakes. These marl deposits are still in process of formation. Marl is in composition, as shown by the following analyses, a comparatively pure lime carbonate, and is correspondingly low in silica, alumina and other impurities. Where used in cement manu- facture it requires the addition of a large amount of clay to bring it to the proper mixture. OYSTER SHELLS. 25 TABLE 6. ANALYSES OF MARLS USED IN AMERICAN CEMENT PLANTS * Silica (Si0 2 ) 1.74 1.78 0.19 0.06 1.19 Alumina (A1 2 0 3 ) 0.901 1.21 f0.05l 0.80 f0.55 Iron oxide (Fe 2 0 3 ) 0.28/ \0.07j \0.25 Lime (CaO) . ... 49.84 49.55 51.31 55.00 52.50 Magnesia (MgO) 1.75 1.30 1.93 1.16 Alkalies (K 2 0 3 , Na 2 0) 1.84 Sulphur trioxide (SO 3 ) 1.12 1.58 0.14 0.05 tr. Carbon dioxide (C0 2 ) ■••■J 46.01 /40.35 42.40 43.22 42.51 Organic matter \ 4.23 2.25 n.d. OYSTER SHELLS, Oyster shells are composed almost entirely of lime carbonate, and as such they could be used in the manufacture of Portland cement. At present, however, they are not so used by any plant in the United States. In regions where oyster canning is carried on extensively oyster shells form an important waste product which is usually disposed of for making shell roads. Where suitable clay can be obtained they might form an important source of Portland cement material. The oyster shells from Biloxi, Mississippi, as shown by the follow- ing analysis, could be used in the manufacture of Portland cement. Good clay can be obtained on Tchouticabouff River. TABLE 7. ANALYSIS OF OYSTER SHELLS FROM BILOXI. Silica (Si02) Alumina (Al 2 Oa) Iron oxide (Fe 2 Oj). . . . Lime (CaO) Magnesia (MgO) Sulphur trioxide (SO 3 ) Volatile matter (C0 2 ). Moisture 5.30 .73 .57 50.25 .45 .25 41.39 ALKALI WASTE. In the manufacture of caustic soda there is a large per cent of waste material in the form of lime carbonate which is sufficiently pure for use as a Portland cement material. The possibility of using the waste product depends on the process used in the alkali plant. In the Leblanc process pyrite is used, ♦Cements, Limes and Plasters, E. C. Eckel, 1905, p. 342. 26 CEMENT MATERIALS. which combines with the lime and forms a large percentage of lime sulphide which renders the resulting waste unfit for use in Portland cement manufacture. In the ammonia process of making caustic soda pvrite is not used and the precipitated waste is largely a mass of lime carbonate. The amount of sulphur, magnesia and other impurities found in the waste depends largely on the character of the limestone used. Where a pure limestone is used the waste forms a cheap source of lime for Portland cement. The following analyses were made from the waste obtained at alkali plants using the ammonia process: TABLE 8. ANALYSES OF ALKALI WASTE * Silica (Si02) 0.60 1.75 1.98 0.98 Alumina (Al*Oi) Iron oxide (Fe*0*) 3.04 0.61 I 1 ' 41 ) 11-38/ 1.62 Lime (CaO) 53.33 50.60 48.29 50.40 Magnesia (MgO) 0.48 5.35 1.51 4.97 Alkalies (K 2 O f Na 2 0) 0.20 0.64 0.64 0.50 Sulphur trioxide (SO*) n.d. 1.26 n.d. Sulphur (S) 0.10 n.d. 0.06 Carbon dioxide (CO*) 42.431 41 70 139.60 n.d. Water and organic matter n.d.J \ 3.80 n.d. SLAG. Slag is a by-product obtained from blast furnaces. In refining metallic ores, especially iron, limestone is most commonly used as a flux. In heating the gangue the lime unites with the silica, the alumina and other materials present in the gangue forming fusible silicates. In the high heat to which it is subjected the limestone gives up a large per cent of lime carbonate which in the slag is changed to the oxide. Slags generally contain from 30 to 40 per cent of lime oxide. Dolomite and highly magnesian limestones render the slag unfit for cement manufacture. Where slag of the proper composition can be obtained in sufficient quantities it may be combined with a pure limestone in the manu- facture of Portland cement. TABLE 9. ANALYSIS OF SLAG USED IN GERMAN PORTLAND CEMENT PLANTS* Per cent Silica (Si02) 30 to 35 Altunina (AI2O3) 10 to 14 Iron oxide (FeO) 00 . 2 to 01 . 2 Lime (CaO) 46 to 49 Magnesia (MgO) 00 . 5 to 03 . 5 Sulphur trioxide (SO j) 00 . 2 to 00 . 6 *Bulletin 243, U. S. Geological Survey, E. C. Eckel, 1905, p. 37. ♦Bulletin 243, U. S. Geological Survey, 1905, p. 38. CLAYS AND SHALE. 27 CLAY* Clays have in their composition alumina and silica with impurities of iron, magnesium, sulphur, alkalies and other minor impurities. The proportion of these ingredients varies from the hydrous silicate of alumina, kaolinite, to the lean sandy clays with barely enough alumina in them to bond them. The value of a clay for use in the manufacture of Portland cement depends on its comparative freedom from impurities. The best clays are those having a greasy, unctuous feel and free from sand. Some clays like those found in the Lafayette formation contain a high per cent of free silica which is not in chemical combination with iron, alumina or lime, and should, therefore, be avoided. Such clays may be well suited for common brick, but ill suited for making cement. A clay which is free from all impurities is hard to find in nature. Residual and transported clays, such as occur in association with the limestones of Mississippi, are apt to contain a large amount of insol- uble material, which is inert in the kiln. The purest clays in the State are those found in the Cretaceous and Tertiary formations. Fortunately for the cement manufacturer clays with a low per- centage of impurities may be used. A study of a large number of analyses of clays now used in American cement plants shows a general average of about 61 per cent of silica, the lowest not below 53 per cent, and the highest not above 75 per cent. “The alumina* and iron oxide together should not amount to more than one-half the percentage of silica, and the composition will usually be better the nearer the ratio Al 2 0 2 + Fe 2 0 3 = ^p is approached.” The average amount of magnesia in 87 analyses of clays and shales now used in American cement plants is 2.21 per cent. Alkalies and iron pyrite should be as low as possible. SHALE. Shale is a product resulting from a mixture of residual materials derived from the decay of all kinds of rocks which have been dis- integrated by mechanical and chemical agencies, carried off and deposited by streams along their channels and at their mouths, and ♦Cements, Limes and Plasters, E. C. Eckel p. 354 28 CEMENT MATER ALS. subsequently hardened by rock pressure. The chemical composition of shale is essentially silica and alumina, while iron oxide, lime, magnesia, sulphur and alkalies are of frequent occurrence. SLATE. Slates are shales and clays which have been formed by lateral compression developing cleavage planes which may or may not be parallel to the planes of deposition. Clays, shales and slates may be used in the manufacture of Port- land cement. Slates require more power to pulverize them and are, for that reason, less used than clays and shales. As a waste product in slate quarries slate can be obtained very cheaply, and where lime- stone is accessible it would form a desirable material in Portland cement mixture. METHODS OF PORTLAND CEMENT MANUFACTURE. The methods of Portland cement manufacture have been greatly improved in the United States in the last decade. Heavy machinery must be installed for crushing the raw materials to an impalpable flour. The enormous cost of erecting a cement plant is largely attributable to the heavy machinery and the fireproof kilns. The processes involved in the manufacture of Portland cement may be divided as follows: Preparing and grinding the raw materials. Burning. Grinding the clinker. PREPARING AND GRINDING THE RAW MATERIALS. One of the essential differences between Portland cement and natural cement is in the preparation of the mixture before burning. The raw materials for a true Portland are intimately mixed in definite chemical proportions and thoroughly ground before burning. In natural cement the stone is burned as it comes from the quarry, without previously being ground and mixed. The chemical propor- tions in a Portland cement can, therefore, the more easily be kept within certain narrow limits. DRY PROCESS. 29 Dry Process. In the dry method of preparing the mixture for the kiln it is necessary to drive off the mechanically held water from the raw materials. The amount of water contained in the raw materials depends upon the character of the rocks and the condition of the weather. All freshly quarried limestones contain more or less hydroscopic or mechanically held water in addition to the chemically combined water. Very compact limestones, such as the oolitic limestones of Tishomingo County, carry from £ to 3 and possibly 4 per cent of water in rainy seasons. The percentage of water in porous chalky limestones, such as the Selma chalk, will, doubtless, in rainy seasons, run as high as from 10 to 15 per cent. The amount of water in chalks will vary in different geological formations, and in different parts of the same formation. Clays and shales are more porous than limestones, and hence carry a greater percentage of water. The amount of water carried will depend on the region, the season, the natural drainage, and the porosity of the material. It has been estimated that the total amount of hydroscopic and chemically combined water in clays may range from 6 to 42 per cent. Where the raw materials are to be finely ground the mechanically combined or hydroscopic water is first removed by some method of drying. In some plants the clays or shales are dried by storing the materials in large sheds. This, however, requires extra shed room, and likewise, additional handling. In most plants it has been found more economical and quicker to dry the raw materials by artificial heat. The materials are usually partially reduced before drying. Before the introduction of the rotary kiln the materials were dried in drying tunnels and on drying floors. The most economical and efficient dryer now in use at the large Portland cement plants of the United States is some type of the rotary dryer, constructed in a manner similar to the rotary kilns. At one plant an ordinary rotary kiln is used for drying the raw materials. In the rotary dryer the materials are introduced into the upper end of the dryer by means of a chute. The combined rotary motion 30 CEMENT MATERIALS. imparted to the dryer and the action of gravity gradually move the materials to the lower end where. they fall on an endless belt and are conveyed to the crushers. In passing through the dryer the materials come in contact with heat and are thoroughly dried. Dry heat is forced into the dryer at the lower end and moves in an opposite direction to the motion of the raw materials. It thus completely envelopes the raw materials and drives off the water of moisture which partially saturates the dry air. At the Edison Portland cement plant of New Jersey, a vertical tower-dryer is used for drying the argillaceous and pure limestones used for making cement. The crushed rock is conveyed to the top of the stack, and by means of the baffle system of screens, which partially retard the speed of the fall, descends through the rising gases of combustion, and is thoroughly dried. The dryer has a capac- ity of 3,000 tons per day, the same as the crusher plant. A piece of rock will pass through the dryer in 26 seconds, reducing the percentage of moisture from 3 or 4 per cent to about 1 per cent. The raw materials are conveyed from the dryer to the crushers and reduced and mixed preparatory to burning. The mixing may be accomplished either before or after grinding. The coarse materials are first crushed in a Gate’s crusher, Blake’s crusher, or in rolls. All of these mills, working upon different principles, reduce the materials so they that can be handled by Huntingdon, or Griffin mills, comminuter or ball mill. Any one of the four latter mills will reduce the materials so that they will pass through a 30-inch mesh. The reduction previous to burning is usually completed in a tube mill where 90 to 95 per cent of mixture should pass through a 100-mesh sieve. In soft materials, such as are found in Mississippi, the entire crush- ing before grinding could be accomplished economically by a com- bination of ball mills and tube mills, or by comminuter and tube mills. In the use of chalky limestone the entire process of reduction may be accomplished in tube mills. The cost of drying depends on the amount of moisture in the raw materials, the type of dryer used, and the cost of fuel. It has been estimated that the most improved dryer will evaporate seven or eight pounds of water per pound of coal. WET PROCESS, SLAG. 31 Wet Process. The wet process of manufacturing Portland cement is best adapted to plants located in the northern States and in Canada, where the raw materials used are frequently fresh-water marls and clay. The marl usually occurs in swamps which are covered with water in wet seasons, and often frozen over in winter. Such plai cs, therefore, can run only a portion of the year. The marls and clays are usually excavated from the pits by means of steam shovels. In some plants the marl is thoroughly mixed with water in the pit and pumped to the mill through pipes. The marl is screened before mixing with the clay to remove pebbles, sticks and roots. The clay in some plants is dried and pulverized before mixing in order to determine more easily the per cent of the mixture. The materials are mixed in the proportion of about 75 per cent of marl and 25 per cent of clay. The mixture is ground in wet mills of the disc type and finally reduced in w T et tube mills. The slurry from the tube mills contains from 30 to 40 per cent of solid matter, and 60 to 70 per cent of water. From the tube mills the slurry is pumped to large tanks and analyzed. If it contains the proper percentages of marl and clay, it is conveyed to the rotary kiln and burned. The daily output of a 60-foot rotary kiln, using the wet process, is from 80 to 120 barrels, as compared with 160 to 180 barrels of a dry mixture. The difference is due to the great amount of water to be removed in the wet process. The cost per barrel in a wet mixture is 30 to 50 per cent greater than in the dry process. PREPARING SLAG FOR CEMENT. In iron -producing districts true Portland cement may also be made from a mixture of blast-furnace slag and pure limestone. The slag contains a sufficient amount of silica and alumina for the mixture. In addition it usually carries from 30 to 40 per cent of lime. By the addition of a pure limestone the proper percentages of a Portland cement are obtained. In American cement plants the two materials are ground separately and then mixed in proper proportions. The mixture is then finely pulverized in tube mills and conveyed to rotary kilns and burned. 32 CEMENT MATERIALS. Where a good quality of slag and limestone can be obtained, the cost of making cement is reduced to a minimum. The process requires but little skilled labor and a relatively cheap plant. Burning, After the raw materials are carefully mixed and ground they are burned to a semi-vitrified mass called clinker, in kilns specially designed for the purpose. The first kilns used in the manufacture of Portland cement were the stationary, intermittent, upright kilns, similar to those now generally in use in burning lime. They have some advantages over the more modem kilns. The original cost of construction is smaller, and less fuel is required. But in this country, where fuel is compara- tively cheap, the object to be attained is as large an output as possible. For this reason, therefore, the rotary kiln has become very popular, and in all the modem, up-to-date plants they have displaced the upright kilns. The upright kilns are still in use in Europe. The rotary kiln is a steel cylinder from 5 to 7 feet in diameter, and from 60 to 150 feet long. It is lined with the best fire brick to withstand the enormous heat necessary to bum the raw materials. The kiln is inclined at about one-half inch to the foot. The mixture to' be burned is fed into the upper end. The rotation of the kiln and the action of gravity gradually force the material through the kiln. In passing through it comes in contact with intense heat generated by the combustion of fuel gases, driving off the water and the carbon dioxide, and forming a chemical combination of lime, silica, alumina and iron oxide. The resulting mass falls out at the lower end of the kiln r as clinker. The fuel is fed into the kiln at the lower end just above the opening through which the clinker falls out. If coal is used as a fuel it is first finely ^crushed and thoroughly dried, and by means of an automatic feeder is forced into the kiln. Fuels. Coal . — The most common fuel used in the manufacture of Portland cement is bituminous coal. A coal high in volatile matter and low in ash has been found to be more desirable than coals containing a high per cent of carbon, such as anthracite and semi-bituminous coals. FUELS. 33 A coal which contains more than 2 per cent of sulphur should not be used. The following table gives the analyses of coals now used in different Portland cement plants in the United States: TABLE 10. ANALYSES OF KILN COALS * Volatile matter 32.90 38.10 31.38 35.41 35.26 39.52 39.37 31.87 37.44 38.00 Fixed carbon 54.66 53.24 58.23 56.15 56.33 51.69 55.82 51.05 53.72 51.72 Sulphur n.d. n.d. n.d. 1.30 1.34 1.46 0.42 n.d. n.d. n.d. Ash 10.25 8.06 9.42 6.36 7.06 6.13 3.81 5.22 5.50 5.38 Moisture 2.19 0.60 1.03 2.08 1.35 1.40 1.00 11.86 3.334 4.90 Before the coal is used in the kiln the large lumps and nut coal are first crushed and reduced to slack in an ordinary crusher. It is then taken to the dryer where all the hydroscopic or mechanically held water is driven off. This is most economically done in a rotary dryer, in much the same way as the raw clay and the limestone are dried. Care should be taken in drying the coal not to raise the temperature high enough to drive off any of the volatile combustible gases. After the coal has been dried it is crushed and pulverized so that at least 85 per cent of it will pass through a 100-mesh sieve. The finer the coal is pulverized the more thorough is the combustion, and the better the results in the kiln. A poor coal, if finely pulverized, will give better results than a higher grade of coal coarsely ground. For this reason it is desirable to get the run of the mines, the origi nal cost of which is cheaper, requires less crushing, and is as good as the hard lump coal. The cost of coal as a fuel depends on the production-cost, the quality of the coal, the kind of kilns used, and the degree of fineness to which it is crushed before using. From 200 to 300 pounds of coal are used in the power plant and in the kilns in the manufacture of a barrel (380 pounds) of Portland cement. The cost of crushing, drying and finely pulverizing the coal, con- veying it to the kilns, allowing for repairs, and interest on a four- kiln plant, will vary from 20 to 30 cents per ton, or about 3 to 5 cents ♦Cements, Limes and Plasters, E. C. Eckel, 1905, p. 513. 2-bl 34 CEMENT MATERIALS. per barrel of cement. In the average plant using coal as a fuel, about one-third of the total cost of the cement may be chargeable to fuel. The question of cheap fuel should, therefore, be an important factor in determining the location of a Portland cement plant. Oil. Oil was formerly used in Pennsylvania Portland cement plants as a fuel in rotary kilns; but its use has been abandoned for coal. Oil is used in some of the wesem plants where good heating coals cannot be obtained at reasonable prices. It is claimed that from 11 to 14 gallons of oil, used in a rotary kiln, will bum one barrel of cement. On this basis, 1 gallon of oil is equivalent to about 20 pounds of coal. Natural gas. — In sections of the country where there is natural gas it is found to be a very economical fuel. The gas is fed into the kiln by means of a large gas burner. It is found to be as good a fuel as coal and requires much less labor and storeroom to feed it to the kiln. Produce gas. — At present there are three cement plants in the United S’ rs using producer gas as a fuel. Only one of these has bee: successful in obtaining an economical fuel consumption. It has bee. . shown by experiments carried on by the United States Geological Survey Coal-testing Plant at St. Louis, that the best quality of producer gas is obtained from bituminous coals and lignites. This gas tan be ignited in internal combustion engines for the develop- ment of power, with a fuel economy of more than 50 per cent. A number of bituminous coals were converted into producer gas and burned in gas engines with a gain in power of 2.6 per cent more than when coal was burned under a common boiler in the production of steam power. It was further shown that gas of a higher quality can be obtained from lignites and low grade coals than from the best Pennsylvania and West Virginia bituminous coals. The gas obtained from a ton of lignite, and burned in a gas engine, produced as much power as a ton of the best bituminous coal burned under a common boiler. In his investigations of the lignites of Mississippi Dr. Calvin S. Brown, assistant geologist of the State Survey, has shown that there are a large number of workable veins of lignite in the State. It is quite possible, therefore, that a high quality of producer gas could GRINDING THE CLINKER. 35 be made from the lignites of Mississippi, and a more economical power produced than can be obtained by using Alabama, Kentucky and Illinois coals. TABLE IU ANALYSES OF MISSISSIPPI LIGNITES. Moisture 13.61 12.51 13.50 8.72 14.61 14.90 Volatile matter 37.14 41.40 39.66 34.64 38.51 39.21 Fixed carbon 42.10 33 .93^ 36.50 22.84 39.10 35.57 Ash 7.15 12.16 10.34 33.80 7.78 10.32 Total 100.00 100.00 100.00 100.00 100.00 100.00 Sulphur 2.64 2.77 4.10 2.76 1.28 0.56 Moisture 15.22 13.04 14.60 13.20 12.26 11.61 Volatile matter 42.38 36.68 30.59 40.16 37.43 34.61 Fixed carbon 34.91 35.62 35.21 31.24 41.91 42.47 Ash 7.49 14.66 11.60 15.40 6.37 11.31 Total 100.00 100.00 100.00 100.00 100.00 100.00 Sulphur 0.91 0.48 1.83 1.20 0.94 2.66 GRINDING THE CLINKER. As the burned clinker emerges from the rotary kiln it has a tem- perature ranging from 300° F. to 2,500° F., or about 13* per cent of the total amount of heat utilized in the kiln. Before it can be crushed the clinker must in some way be cooled. A number of devices have been invented to cool the clinker in the most rapid and at the same time in the most economical way. In some plants the hot clinker, on its journey from the kiln to the storage room, is subjected to a spray of water, the evaporation of which absorbs the heat of the clinker. In this method of clinker-cooling none of the heat of the clinker is utilized. Since the amount of heat carried off in the clinker is so great, efforts have been made to utilize the heat of the cooling clinker. This has been the most successfully done by the two-stage rotary cooler. The principle on which the cooling is done is here summarized from a description of the. cooling system at the main Atlas cement plant, by Stanger and Blount in Proc. Inst. Civil Engineers, Vol. 145, pp. 57-68, 1901. The hot clinker from the kiln falls into a rapidly revolving cylinder about 30 feet long and 3 feet in diameter, otherwise similar in con- struction to the rotary kiln. At the end of the cylinder opposite the kiln is admitted a blast of cool air which passes through the cylinder, 36 CEMENT MATERIALS. cools the clinker, and is admitted into the kiln in a highly heated condition. At the end of the first cylinder the clinker passes through a crusher which is kept cool by a spray of water. The clinker passes from the crusher through a second cylinder, 60 feet long and 5 feet in diameter. From the second cylinder the clinker is conveyed to the crushers. In burning the raw materials at a high temperature the clinker thus formed is a very hard semi-vitrified mass which must be pulver- ized to a fine flour before it can be called cement. The best Portland cements are now ground so that from 90 to 95 per cent will pass a 100-mesh sieve. The process requires a great amount of power and heavy machinery. It is estimated by Mr. E. C. Eckel that, in a Portland cement plant using the dry process of manufacture, it requires about the same amount of power and similar machinery to crush the clinker as that used in crushing the raw materials. “It must be remembered that for every barrel of cement produced, about 600 pounds of raw ma- terial must be pulverized, while only a scant 400 pounds of clinker will be treated ; that the large crushers required for some raw materials can be dispensed with in crushing clinker, and that the raw side rarely runs full time.”* RETARDER FOR QUICK-SETTING CEMENTS. A small amount of calcium sulphate, usually in the form of crude gypsum or plaster of Paris, is necessary in the manufacture of Port- land cement to retard the quick-setting, high-limed clinker produced in the rotary kilns. The amount used in most American plants varies from 2 to 3 per cent. Used in large quantities it may even accelerate the set and greatly weaken the cement. The calcium sulphate should be intimately mixed with the cement, and that this may be thoroughly done it is usually put in and ground with the clinker. PORTLAND CEMENT MATERIALS OF MISSISSIPPI. GENERAL GEOLOGY. Cement materials of Mississippi consist of hard limestones, chalk, clays and shales. Inasmuch as the chalk of this State is a compara- tively hard rock it will be treated as a limestone. Limestone, the principal ingredient necessary in the manufacture of Portland cement, is found in four geologic periods of the State, * Limes, Cements and Plasters, 1906, p. 631. DEVONIAN ROCKS. 37 widely differing from each other in age and location. In each period shales or clays overlie the limestones. The four periods will be described in the order here given. (1) Devonian. (4) Tertiary. (2) Carboniferous. Vicksburg limestone. (3) Cretaceous. Selma chalk. Devonian. Along the Tennessee River, and for a distance up all the streams flowing into the Tennessee from the State of Mississippi, are beds of limestone representative of the Lower Devonian. The line of separa- tion of the Devonian and Carboniferous rocks has not been mapped in Mississippi. The Devonian rocks are represented by a dark gray limestone and interbedded shales, with an occasional stratum of fine- grained standstone. The limestone contains a high per cent of insol- uble matter which occurs in chemical combination and not in the form of free silica or sand. The following section of the Devonian on Yellow Creek, Tisho- mingo County, was obtained by the writer:* Section of Devonian on Yellow Creek. Sec. 22, T. 1 N., R. 10 E. Thin-bedded, impure limestone at base, changing gradu ally to a bluish limestone at top of cliff Compact blue limestone, non-fossiliferous Dark gray limestone containing numerous Devonian fos- sils 10 Dark pure limestone to water’s edge 5 On the north bank of Yellow Creek, near its mouth, the limestone is overlain by thin strata of aluminous sandstone and shale. A reproduction of the outcrop near the mouth of Yellow Creek is found on Whetstone Creek near Short postoffice. Section on A. L. Bugg’s Land , near Mouth of Whetstone Creek . t Feet 100 30 20 ♦Geology and Mineral Resources of Miss., U. S. Geol. Surv. Bull. No. 283, p. 9. tlbid p. 10. Angular chert, flint and hornstone Dark blue shale containing iron pyrite; very fossiliferous in lower part Thin-bedded, fine-grained, shaly limestone, with thin bands of fine-grained sandstone or whetstone varying from a fraction of an inch to 12 inches in thickness. . Feet 95 40 38 CEMENT MATERIALS. It is quite probable that the dark blue limestone which is found at the mouth of Bear Creek is the uppermost member of the Devonian. The Devonian of this State includes shale and limestone suitable for hydraulic and Portland cements. TABLE 12. ANALYSES OF DEVONIAN LIMESTONE FROM TISHOMINGO COUNTY. 1 2 3 4 Insoluble matter (Si02) 54.201 35.281 42.00 48.18 Alumina (A1 2 Oj) 1.064 1.914 1.98 3.43 Iron oxide (Fe*Oj) 0.903 1.581 6.02 3.13 Lime (CaO) 23.247 32.603 23.25 39.47 Magnesia (MgO) 0.788 0.630 0.27 3.19 Carbonic acid 15.572 1 | 27.643 | ' *24.10 5.06 Organic matter and water 3.752 j 0.40 0.40 Potash 0.473 0.348 Sulphur trioxide 1.50 2.23 1, 2. Dr. E. W. Hilgard, analyst. 3, 4. Dr. W. F. Hand, analyst. Carboniferous. The Carboniferous rocks in Mississippi include beds of limestone, shale, chert and sandstone extending in age from the Ordovician to and including the Mississippian. Oolitic limestone suitable for the manufacture of Portland cement is found near the top of the Carbon- iferous rocks in Mississippi, and is the equivalent of the St. Genevieve limestone of western Kentucky, and the famous building stone of Bedford, Indiana. In Alabama this rock is quarried for burning lime and building stone. The oolitic limestone is dark gray to white, and is made up almost exclusively of small, rounded concretions called oolites. It is practi- cally free from impurities. A thickness of 30 feet or more is exposed in the bluffs on Bear Creek as far south as Mingo. The distribution of the oolitic limestone and accompanying shales is confined to that part of Tishomingo County lying north of Mingo, along Bear Creek and its tributaries, and in one locality on Macky’s Creek. In the hills to the west the Paleozoic rocks are covered by later deposits of Cretaceous and Lafayette. On the west side of Cypress Pond, about 1 mile north of west of the steel bridge across Bear Creek near Mingo, on land now belonging to Mr. William Southward, the limestone forms a bluff 30 to 35 feet high. Its thickness below the surface has not been determined. The *Volatile matter. CARBONIFEROUS ROCKS. 39 limestone is overlain by a bed of dark blue shale which weathers to a tough blue clay. The top of the limestone along the pond has about the same elevation as the base of the shale bed in the section at the steel bridge given below, so that the two may be taken together as one continuous section, the one at the bridge being a continuation upward of the Cypress Pond section. Limestone outcrops in many of the branches flowing into Cypress Pond, and is frequently struck in wells on the west side of Bear Creek. Still farther north, on the Allsboro and Iuka road, the oolitic limestone outcrops in sections 22, 26 and 27, T. 4 N., R. 11 E. The oolitic limestone near Mingo is overlain by a bed of shale 23 feet thick, separated by a thin stratum of impure limestone 8 inches thick. The following is a section of the bluff at the steel bridge near Mingo: Section of the Bluff at the Steel Bridge near Mingo. Residuary soil and Lafayette at the surface x feet Heavy-bedded limestone about 20 feet Compact, blue shale 15 feet Thin ledge of impure limestone, upper 3 inches studded with fossils 8 inches Thinly laminated blue shale with an occasional frag- ment of impure dark limestone, water’s edge 8 feet The lowest shale bed is thinly laminated and contains more or less fine sand between the laminae. The upper bed is more thickly lami- nated and freer from impurities. The composition of the above limestones and shales is given below : TABLE J3. ANALYSES OF CARBONIFEROUS LIMESTONES AND SHALE. TISHO- MINGO COUNTY. 1 2 3 Silica (Si02) 1.57 10.91 54.46 Alumina (Al 2 Oa) 1.94 8.17 14.92 Iron oxide (Fe 2 03 ) 1.69 5.00 12.50 Lime (CaO) 52.75 47.06 2.56 Magnesia (MgO) 36 0.16 0.00 Volatile matter (C0 2 ) 40.80 27.00 13.30 Sulphur (SOj) 32 0.85 .85 Moisture 1.10 2.30 99.48 100.25 100.89 1. Limestone from Cypress Pond near William Southward’s house. 2. Limestone from Mingo bridge, Bear Creek. 3. Shale from Mingo bridge, Bear Creek. 40 CEMENT MATERIALS. CRETACEOUS. TUSCALOOSA CLAYS. The Tuscaloosa clays are well displayed in northeastern Missis- sippi. They have been more carefully studied in Tishomingo County, where they occur in thick deposits over large areas. These clays overlap the Carboniferous and Devonian limestones and in some cases outcrops of limestone and clay occur in the same section. The following analyses are characteristic of the clays of Tisho- mingo and Itawamba counties: TABLE 14. ANALYSES OF TUSCALOOSA CLAYS OF MISSISSIPPI * Silica (Si0 2 ) if •S'S i o g £ 0 1 O J Magnesia (MgO) Sulphur trioxide (SO*) Moisture Loss on ignition Pink clay, 6 miles north of Iuka, Tishomingo County t38.11 36.42 11.73 .60 .14 Tr. .87 11.96 White clay, 6 miles southeast of Iuka, Tishomingo County t66 . 85 20.54 3.77 .21 .18 Tr. .59 8.00 White potter’s clay, 5 miles south of Iuka, Tishomingo County t68.65 18.99 2.77 .20 .20 Tr. 1.09 7.34 White clay, 5 miles south of Iuka, Tishomingo County J80.07 11.46 .57 .12 .37 n.d. ! X6.81 .60 Tuscaloosa clay, 15 miles south of Iuka, Tishomingo County t80.03 12.00 1.68 .24 .26 Tr. .48 4.82 Tuscaloosa clay, 12 miles south of Tiilra Tishomingo County §90.877 2.214 .126 .140 Tr. n.d. X6.93 White potter’s clay, 14 miles south- east of Fulton, Itawamba County t59.12 27.44 4.39 .34 .28 Tr. .54 7.40 White potter’s clay, 14 miles south- east of Fulton, Itawamba County t62.58 27.58 1.57 .40 Tr. Tr. .77 6.77 Tuscaloosa clay, 14 miles southeast of Fulton. Itawamba County. . . . t71 .53 14.46 4.14 .62 .55 n.d. 2.17 S 5.91 SELMA CHALK. The Selma chalk of Mississippi includes a great thickness of chalky limestone commonly known as “rotten limestone” of Cretaceous age. In Bulletin No. 283, U. S. Geological Survey, the writer describes the Selma chalk as “a mass of loosely semi-cemented lime carbonate, the ♦Bull. 283 U. S. Geological Survey, Crider, pp. 51-55. tW. F. Hand, State chemist, analyst. tJ. Blodgett Britton of Philadelphia, Pa., analyst. §Dr. E. W. Hilgard, analyst. X Water and organic matter. SELMA CHALK. 41 upper division of which is of exceptional purity. Where it is typi- cally exposed along the larger streams it bleaches to a white appear- ance and is called the ‘white chalk’ bluffs. To the casual observer the entire formation has much the same appearance, but it may be separated into three natural divisions, based primarily on chemical analysis, (a) the transition beds at the base, (6) the ‘blue rock,’ or more clayey un weathered portion, and ( c ) the rotten limestone, or chalk, including the upper portion of the formation. “(a) The lowest division contains a large amount of free sand which was washed into the Selma sea from the Eutaw and the older land sur- face to the east. This forms the transition beds from the extremely sandy strata of the Eutaw to the deep-sea deposits of lime carbonate which characterizes the Selma chalk. The amount of sand is greatest at the base and becomes less and less upward until it finally disappears entirely.” This lower portion would not be suitable for cement on account of the great amount of free sand it contains. Fortunately, however, the sandy portion is confined to the lower division of the formation and can be easily avoided in using the overlying limestone for cement. ‘‘(6) The middle division contains a relatively large amount of clay and when freshly dug is of a bluish color. It is found in the deep wells and recognized by the drillers as ‘blue rock.’ The great amount of clay in the lime carbonate renders the rock impervious to water. The fine supply of artesian water stored in the underlying Eutaw sands is held in place and prevented from escaping upward by means of the ‘blue rock’ of the Selma. (i c ) ‘‘The uppermost division contains a greater amount of lime carbonate and much less clay than the ‘blue rock’ and likewise a smaller amount of free silica than the lowest division. Some of the analyses of this chalk show 98 per cent of calcium carbonate. ‘‘In places a hard crystalline limestone, somewhat silicified, forms a capping to some of the hills of the Selma. Hard flint rock and a thin strata of sandstone are reported in a deep well-boring at Liv- ingston, Ala.” The Selma in Mississippi corresponds to the formation of the same name in Alabama. The white chalk bluffs along Tombigbee, Warrior and Alabama rivers may be seen in numerous places in Dallas, Hale, 42 CEMENT MATERIALS. Sumter and Green counties, Alabama. It is all of the same geologic age, and once known it may be easily recognized. THICKNESS. The Selma attains its greatest thickness in central Alabama, where it is reported to be 1,200 feet. It decreases in thickness to the east, disappearing entirely in the eastern part of the State. East, of Mont- gomery the three divisions are mapped as one formation. In western Alabama it has a thickness of 925 to 950 feet, while in Oktibbeha County, Mississippi, it has a thickness of about 800 feet. From this point northward the formation continues to thin and finally disappears entirely near Camden, Tennessee. The area of the State underlain by the Selma is shown by the light green on the map. The region is known as the “prairies” and may be easily recognized by the dark rich loams at the surface. The disintegration of the Selma forms one of the richest soils in the State. In Alabama the Selma area forms one of the richest cotton belts in the South and is known as the “Black belt.” In comparatively recent geologic times the entire area of the Selma was covered by the Lafayette, a thin deposit of sandy loam. The greater part of the Lafayette has been carried away by the streams. In the inter-stream areas however, and on the more level lands near the streams, there are still small patches of Lafayette which have suffered but little erosion since its deposition. In consequence of this fact there are two distinct and widely different soils which are found in this region. These are the “post oak” and the “prairie” soils. The Lafayette in this area has a maximum thickness of about 13 feet. The “post oak” soils are usually found on the higher inter-stream areas where there has been least erosion. . The soil is poor and pro- duces a scrubby growth of post oak and black jack. In the early settlement of the region the “post oak” land was first cleared, but at present it is mostly used for grazing. The “prairie soils” are found on the rolling lands from which the Lafayette has been entirely removed so that the rich black loam, formed by the disintegration of the -underlying Selma limestone, is at the sufrace. The “prairie soils,” therefore, are residual soils in situ , and form the most fertile lands of eastern Mississippi. SELMA CHALK. 43 In places all the Lafayette and even the residual soil of the Selma have been removed by erosion, leaving the white chalky limestone of the Selma at the surface. On looking for the outcropping Selma it may be more readily found along the streams, on the steep hillsides and in the railroad cuts. Inasmuch as this is to be the final report on the cement materials of the State for some time, space will be taken to describe a large number of outcrops of the Selma limestone, much of which is very similar in appearance. A fair series of analyses has been made of the limestone from different localities, giving some idea of the value of the Selma for cement. It must be understood, however, that at no locality has the Selma been found to contain all the constituents necessary in the manufacture of either hydraulic or Portland cement. It becomes valuable as a cement product when used in connection with clay. All the limestone found in the Selma area is not of value for cement because of the lack of good clay near it. Only those out- crops, therefore, which are near good clay outcrops can profitably be utilized for cement. The clay in the geologic section immediately overlying the Selma, known as the Porter’s Creek, is suitable for mix- ing with the limestone. The possibility of using this clay will be taken up under the head of Porter’s Creek clay. DISTRIBUTION. That part of the State embraced within the area represented on the map by the light green color is underlain by the Selma chalk. The limestone does not show at the surface over the entire area shown on the map owing to the covering of sandy loam and residual soil which, over the greater part of the area, completely covers the limestone. This covering is comparatively thin, as is shown in wells, railway cuts, along the streams and on many hillsides where the atmospheric waters have carried away the soil covering, leaving the Selma limestone exposed at the surface. Corinth and Vicinity . — The town of Corinth is built in the valley of a small stream which flows into Tuscumbia River. On the west side of the town is a low range of hills which rise 30 to 40 feet above the valley. About J of a mile west of the station on the Southern Railway, is a cut through a small ridge showing from 5 to 8 feet of surface sandy loam, with an equal thickness of Selma limestone, 44 CEMENT MATERIALS. which extends to the bottom of the cut. The Selma at this place can hardly be called a limestone. It is the “blue rock” which occurs near the bottom of the formation, and is more properly a compact calcareous clay which can be broken into rectangular blocks. There are small needle-like crystals of selenite in the cracks and on exposed surfaces. The thickness of the Selma at Corinth is less than 100 feet. TABLE 15. ANALYSIS OF SELMA LIMESTONE FROM CORINTH. Silica (SiOj) Alumina (AljOi) Iron oxide (Fe 2 Oi). . . . Lime (CaO) Magnesia (MgO) Volatile matter (C0 2 ). Sulphur trioxide (SO*) 92.19 25.40 6.88 8.62 26.37 .58 23.70 0.64 The above analysis shows a high per cent of silica, which is char- acteristic of the lower beds of the Selma. Higher in the formation the percentage of lime steadily increases, while the siliceous ma- terial decreases correspondingly. Purer limestone is found in the railway cuts west of Corinth. The Selma may be found underlying the surface covering for 6 to^lO miles west of Corinth, and for 3 miles east. It gradually thins to the east and finally disappears completely in the low north and south range of hills 3 miles east of town. At the western end of the 90 foot cut on the new line of the Illinois Central Railway, 3 miles east of Corinth, the blue limestone of the Selma extends to the bottom of the cut. At the eastern end it forms a thin stratum and finally disappears completely. The lowest mem- ber of the Selma is underlain by a bed of oxidized, calcareous, sand- bearing fossils. The Selma is exposed in almost every cut of any size along the Southern Railway from Corinth to the Tennessee State line. A few hundred yards west of Wenasoga, 12 feet or more of bluish calcareous clay are exposed in the railway cut. At this point the Selma is much thicker than it is at Corinth. At the little town of Chewalla, across the line in Tennessee, it was penetrated in a well at a depth of 350 feet. There is quite a thickness of overlying transported soil, so that the limestone is at least 300 feet thick. SELMA CHALK. 45 The Selma is encountered in digging wells at Danville, Rienzi and Thrasher, but these towns are near the eastern edge of the Selma, which, as is shown by the well records, contains more or less sand. These towns are located on the Mobile and Ohio Railway, which follows along the second bottoms of the Tuscumbia River, and consequently there are no outcrops of the Selma at the surface. Booneville and Vicinity . — In the deep cut on the Mobile and Ohio Railway, in the town of Booneville, the typical Selma limestone is exposed. There is a thick covering of sandy loam (Lafayette) over- lying the limestone in the vicinity of Booneville. Many of the wells obtain their supply of water from the base of the Lafayette. The compact nature of the Selma prevents the water from penetrating it. There are many small springs found at the contact between the Lafayette and the underlying Selma. The following record of the Booneville Waterworks Company’s well, furnished by Mr. A. W. Hurley, driller, will give some idea of the thickness of the Selma at this place: Section of Booneville Waterwork's Well. 13. Surface red clay 12. Selma “blue rock” 11. Bluish green sandy clay with shells 10. Blue sand containing water 9. Hard rock 8. Blue sand containing water 7. Blue hard rock 6. Clay (“soapstone”) .. . 5. Sand 4. Clay (“soapstone”) . . . 3. Sand 2. Hard rock at 307 feet 1. Gray sand containing green sand grains Feet 18 52 3 40 1 7 4 188 4 35 Total depth of well 347 From the above record it will be seen that the limestone at Boone- ville is 52 feet thick. One-fourth of a mile east of this town it is or ly 25 feet thick, and f of a mile east it cuts out entirely. It outcrops in the hills west of the town and is encountered in all the deep wells as far west as Jumpertown. The Mobile and Ohio Railway follows, approximately, the eastern limit of the Selma between Booneville and Tupelo. The eastward extension of the Selma at Booneville is due to the fact that the divide between the waters of Tuscumbia and 46 CEMENT MATERIALS. Tombigbee rivers have suffered but little erosion. South of the divide the headwaters of Tombigbee River have carried away a large amount of the Selma and caused the contact between the Selma and the underlying Eutaw green sands to swing westward in the vicinity of Wheeler, Baldwin and Guntown. jj| At Guntown the lowest beds of the Selma are exposed in the railway cut just north of the station. There is a compact ledge of fossiliferous limestone about 2 feet thick underlain by a bed of green sand which extends to the bottom of the cut. This doubtless cor- responds to strata No. 11 in the Booneville section. There is a strong southward dip of the Selma as shown in the railroad Cut at Guntown. The main body of the Selma lies west of Guntown. The basal mem- bers here, as at all other places where they are exposed, contain too much sand to be used in the manufacture of Portland cement. Tupelo and Vicinity . — The town of Tupelo is built in the valley of Old Town Creek, a large tributary to Tombigbee River. In the lower portions of the town the alluvial soil is 20 feet thick. The hills to the east have a thin covering of Lafayette. To the northwest the Lafayette and residual Selma form the fertile farming lands. The only evidence of the presence of the Selma here is found in the wells which extend below the surface soils. Below is a record of an average artesian well in Tupelo: Well Record at Tupelo. R. B. McVay, Driller. Feet Surface soil 20 “Blue rock” with some sand (Selma) 100 Blue limestone (Selma) 130 Fine gray sand, water-bearing 10 Clay (“soapstone”) 4 White sand, water-bearing 10 Clay (“soapstone”) 20 Fine white sand, thickness undetermined. The above record shows 230 feet of Selma limestone. The upper 100 feet of “blue rock” is reported as containing some sand. This is perhaps a calcareous green sand or else it is a horizon in the Selma not yet discovered at the surface. The latter theory is hardly prob- able, however, since so great a thickness would not have escaped detection in the detailed work done on the formation in Alabama and along the Tombigbee River in Mississippi. SELMA CHALK. 47 The first cut on the Mobile and Ohio Railway south of Tupelo exposes the Selma from the surface to the bottom of the cut. All the deep cuts from here to Verona penetrate the surface soils and reach the Selma. It also outcrops on the sides of the wagon road and in the open field about miles south of Tupelo. In other places along the road between Tupelo and Verona, and in numerous places west of Verona, the Lafayette has been removed by erosion, exposing the Selma. On the more level lands the residual soil of the Selma forms the well known “prairie soil.” During the rainy season the constant kneading of the “prairie soil” by wheels of vehicles and horses’ feet forms a tough plastic clay which, when once recognized, may never be mistaken. Even if there is no outcrop of the Selma near, the “prairie soil” indicates that the Selma is but a few feet, or perhaps a few inches, below the surface. A sample of the Selma collected from the roadside about 2J miles south of Tupelo shows the following analysis. TABLE 16. ANALYSIS OF SELMA LIMESTONE 2* MILES SOUTH OF TUPELO. Silica (Si0 2 ) 22.76 Altunina (AI 2 O 3 ) 4.56 Iron oxide (FeaOs) 6.46 Lime (CaO) 34.31 Magnesia (MgO) .05 Volatile matter (CO 2 ) 28.25 Sulphur trioxide (SO 3 ) .43 Moisture 2.10 Fine exposures of the Selma are found on Coonewah Creek about 5 miles west of Tupelo. It is overlain in places by 6 to 10 feet of yellow clay. The Selma continues westward to within 3 or 4 miles of Pontotoc. In southeastern Pontotoc County it is reported to be 750 feet thick. A sample of Selma collected by W. N. Logan from a point 1 mile west of Tupelo, on the Tupelo and Pontotoc road, shows the follow- ing analysis: TABLE 17. ANALYSIS OF SELMA LIMESTONE 1 MILE WEST OF TUPELO. Silica (Si0 2 ) 14.84 Alumina (AI 2 O 3 ) 15.59 Iron oxide (Fe 20 a) 4.50 Lime (CaO) 32.89 Magnesia (MgO) .41 Volatile matter (CO 2 ) 27.10 Sulphur trioxide (SO3) 3.30 Moisture 1.08 99.71 48 CEMENT MATERIALS. The thickness of the Selma as shown in the wells at Verona is about the same as it is in Tupelo. The following is a record of one of the wells in Verona: Well Record at Verona. R. B. McVay, Driller. Feet Surface soil 21 Light colored Selma 80 Blue limestone, Selma 160 Gray sand, water-bearing 10 Compact, sticky sand 30 Gray sand, water-bearing 15 Black clay, “soapstone” 20 Fine gray sand, water-bearing x The entire thickness of the Selma here is 240 feet. No sand is reported from the upper 80 feet as in the well at Tupelo. The well is located in the lowest part of the town near the station. The Selma comes to the surface in places just west of town. Okolona and Vicinity . — One of the best exposures of the Selma limestone in the northern and central portions of the Selma area is found in the town and vicinity of Okolona. In a few places the Lafayette sandy loam is present, but from the greater portion of the area it has been removed, leaving large patches of exposed lime- stone known as “bald prairies.” The limestone has become white by reason of long exposure to sun and rain. In this respect it resembles the “white chalk” exposed in the bluffs along Noxubee and Tom- bigbee rivers. The numerous outcrops of the Selma in southeastern Chickasaw and western Clay counties have been carefully described by Dr. Hilgard.* The country is dotted with outcrops of the Selma along Chooka- tonkchie, Houlka, Oka Tibbeha or Tibby creeks, and on the eastern slope of Pontotoc Ridge, projections of which extend southward between the above mentioned streams. The limestone in north- western Clay County has been penetrated in wells at a depth of about 500 feet. A sample of the limestone from the railroad cut at the Mobile and Ohio station, Okolona, was burned in a forge for a period of 15 min- * Agriculture and Geology of Mississippi, pp. 79-81. SELMA CHALK. 49 utes. The rock was heated to a white heat and slaked by pouring water on it. It immediately broke down into a beautiful white lime. The following analyses were made of this limestone: TABLE 18. ANALYSES OF SELMA LIMESTONE FROM OKOLONA. 1 2 Silica (Si0 2 ) 8.80 8.70 Aluimna (A1,0«) 2.86 0.00 Iron oxide (Fe 2 03 ) 4.08 6.00 Lime carbonate (CaO) 45.51 45.62 Magnesium carbonate (MgO) .36 1.72 Volatile matter (C0 2 ) 31.11 34.40 Sulphur trioxide (SO 3 ) .38 1.11 Moisture 6.35 1.10 The following analysis of the same limestone was made by Dr. E. W. Hilgard.* Insoluble matter (mostly silica) (Si0 2 ) 10.903 Alumina (Al 2 03 ) 1.957 Peroxide of iron (Fe 2 Os) 1.421 Lime (CaO) +45.791 Magnesia (MgO) +0 . 877 Carbon dioxide (C0 2 ) 35.725 Alkalies (K 2 0, Na 2 0) 0.568 Organic matter and water 2.840 The eastern edge of the Selma south of Tupelo follows, approxi- mately, the boundary between Itawamba and Lee counties south- ward to the Monroe County line. From here to Columbus it is almost a due north and south line, rarely extending more than 3 miles west of Tombigbee River. Outcrops are frequent from the eastern to the western borders of the formation. Starkville and Vicinity . — In the eastern half of Oktibbeha County the Selma limestone is characteristically developed. A few small patches of the Lafayette still remain on some of the divides. The rest of the surface is formed by the residual loam of the “prairie soil,” and the white rock of the Selma. One to ten feet of Selma limestone may be seen in almost every cut along the Illinois Central Railway from Starkville to West Point. Similar outcrops occur along the Mobile and Ohio Railway from Starkville td Artesia. ♦Geology and Agriculture of Mississippi, 1860, p. 101. fEquals lime carbonate (CaCOs) 81.77. ^Equals magnesium carbonate (MgCOs) 1.84. 50 CEMENT MATERIALS. The thickness of the Selma in the city well at Starkville is about 750 feet, with 50 feet or more exposed in the hills to the north. The character of the limestone collected from various localities in Oktibbeha County is shown by the following analyses: TABLE 19. ANALYSES OF SELMA LIMESTONE FROM OKTIBBEHA COUNTY. 1 2 3 4 Average Silica (SiOj) 2.89 2.33 3.03 2.55 2.70 Alumina (A1 2 0 8 ) Iron oxide (Fe 2 Os) | 1..53 1.72 1.92 1.96 1.78 Lime carbonate (CaCOs) 94.10 94.35 93.60 94.07 94.03 Magnesium carbonate (MgCO») . . . 1.84 1.82 1.64 2.12 1.85 Water (H 2 0) .36 .44 .42 .52 .44 By a proper admixture of clay with any of the above samples of limestone the product would make an excellent Portland cement. The per cent of lime carbonate is high with a corresponding low per cent of iron oxide, alumina and magnesium carbonate. The following samples of Selma limestone, collected by W. N. Logan from Oktibbeha County, were analyzed with the following results : TABLE 20. ANALYSES OF SELMA LIMESTONE FROM OKTIBBEHA COUNTY. 1 2 3 4 5 6 Silica (Si0 2 ) 29.98 25.27 9.84 20.60 17.03 18.82 Alumina (A1 2 Oj) 5.45 4.81 .19 7.63 21.00 .23 Iron oxide (Fe 2 0 8 ) 5.60 10.35 2.58 4.62 3.33 2.80 Lime (CaO) 31.62 32.85 38.65 21.81 29.29 40.02 Volatile matter (C0 2 ) 24.50 25.60 42.05 23.15 28.20 34.02 Magnesium oxide (MgO) .14 . 84 .18 . 81 0.00 . 96 Sulphur trioxide (SOj) .21 .62 2.05 .25 .72 2.53 Moisture 1.50 .40 .94 .85 .75 1.15 1. Agricultural College. 2. Near Osborn. 3. Reynolds farm, 1 mile west of Starkville. 4. Howard Brick Yard, Starkville. 5. Howard Brick Yard, Starkville. 6. Mayhew road, 1 mile east of Agricultural College. The occurrence of Selma limestone in southern Monroe, Lowndes, Noxubee and Kemper counties has been described in detail by the writer in Bulletin 260, U. S. Geological Survey, 1904, pp. 510-521. A large number of samples from these counties were collected and analyzed in the U. S. Geological Survey laboratory. Macon and Vicinity . — The limestone at and near Macon deserves special mention on account of the large amount of material in sight, Plate I SELMA CHALK BLUFF, MACON, SELMA CHALK. 51 the ease with which it could be quarried, the nearness to deposits of clay and the facilities offered for transportation. The bluff on Noxubee River at the mouth of Macon Creek, near the town of Macon, is about 40 feet high, and extends more or less unbroken to the mouth of the Noxubee River. The entire bluff, except 5 or 10 feet of surface soil, is formed of the Selma limestone. Other outcrops occur along all the principal streams flowing into the Noxubee River, and in the railway cuts as far south as Scooba. The limestone, viewed from a distance, appears to be a homo- geneous mass of white chalk. On close examination, however, it is found to have an amygdaloidal structure, as if small fragments of limestone had been cemented into a compact mass. There are few joints or stratification lines visible. Occasional concretions of iron pyrite ranging from the size of a buckshot to a hen’s egg occur imbedded in the limestone. After long exposure to the weathering agents the sulfide of iron changes to the oxide, leaving rusty iron stains on the rocks. The following analyses were made of the limestone from the bluff at Macon: TABLE 21. ANALYSES OF SELMA LIMESTONE FROM MACON. 1 2 Silica (Si0 2 ) 9.09 13.03 Alumina (AUOj) 1 , 4y ^ Lime carbonate (CaCOs) 80.99 76.71 Magnesium carbonate (MgCOs) .00 .36 Water 1.08 .95 Sulphur trioxide (SO 3 ) 0.00 .64 1 . W. S. McNeil, U. S. Geol. Survey, Analyst. 2. W. F. Hand, State Chemist, Agricultural College, Analyst. A sample of limestone was collected from the ridgeland 3 miles north of Macon and analyzed in the laboratory of the U. S. Geological Survey with the following results: TABLE 22. ANALYSIS OF SELMA LIMESTONE FROM 3 MILES NORTH OF MACON. (W. S. McNeil, Analyst.) Silica (Si0 2 ) 8.52 Alumina (A1 2 0 3 ) 1 6 6 q Iron oxide (Fe 2 03 ) / Lime carbonate (CaCOs) 83.88 Magnesium carbonate (MgCOs) -00 Water l-°° 52 CEMENT MATERIALS. Still another sample of the Selma was collected from Prairie Rock, 12 miles east of Macon. This rock is much harder than the ordinary Selma and breaks with a metallic ring. It has been used to some extent for building roads near Prairie Rock, but it soon breaks down into soil under the action of the weathering agents. A sample of this limestone was analyzed in the laboratory of the U. S. Geological Survey with the following results: TABLE 23. ANALYSIS OF SELMA LIMESTONE FROM PRAIRIE ROCK. (W. S. McNeil, Analyst.) Silica (Si0 2 ) 1.13 Alumina (A1 2 0 3 ) 1 Iron oxide (Fe 2 0 3 ) j Lime carbonate (CaCOj) 98.36 Magnesium carbonate (MgC0 3 ) Tr. Water .40 In southwestern Lowndes County excellent Portland cement materials are found along the divide between Tombigbee and Noxubee rivers. On Mr. J. B. Brook’s land near Crawford, much of the overburden has been removed, leaving the white Selma chalk at the surface. The limestone from this place contains about the proper proportions of lime carbonate, alumina and iron oxide for Portland cement. There is a small amount of magnesia, but not enough to injure it. To make a suitable cement this limestone must be mixed with a clay containing a low per cent of silica. TABLE 24. ANALYSIS OF SELMA LIMESTONE FROM CRAWFORD. (Analysis furnished by J. B. Brooks.) Silica (Si0 2 ) 8.88 Alumina (A1 2 Oj) 1 5 94 Iron oxide (Fe 2 0 3 ) J Calcium carbonate (CaC0 3 ) 79.73 Magnesia (MgC0 3 ) 1.22 Loss 1.88 A residual clay of the Selma limestone from the same locality was analyzed with the following results. This clay, while it is a fairly good one, contains a rather high per cent of iron oxide and alumina to use with the limestone. Plate II. RESIDUAL CLAY AND LAFAYETTE OVERLYING SELMA CHALK, MACON. SELMA CHALK. 53 TABLE 25. ANALYSIS OF CLAY FROM CRAWFORD Silica (SiOs) Alumina (Al 2 Os) Iron oxide (Fe 2 Oa) Calcium carbonate (CaC0 3 ) Magnesium carbonate (MgC0 3 ) Loss The Selma limestone may be seen along many of the streams, and in the railway cuts between Macon and Scooba. As a general thing there is only a thin covering of overburden on the -ridges and slopes. Five miles east of Shuqualak, Noxubee River has cut into the Selma limestone and formed a bluff on the east bank 50 feet high. A sample of this limestone collected by the writer* and analyzed in the laboratory of the U. S. Geological Survey, gave the following results: TABLE 26. ANALYSIS OF SELMA LIMESTONE 5 MILES EAST OF SHUQUALAK. (W. S. McNeil, Analyst.) Silica (Si0 2 ) 8.06 Alumina (A1 2 0 3 ) 1 ,-04. Iron oxide (Fe 2 0 3 ) / Lime carbonate (CaCOj) 84.61 Magnesium carbonate (MgC0 3 ) .06 Water 1.32 The high percentage of silica in the Selma at Wahalak, Bodea Creek and Scooba, indicates a change from the deep sea in which the Selma was deposited, to the more shallow waters which received the more siliceous deposits of the Ripley and the Porter’s Creek forma- tions. The following analyses! of Selma limestone were made in the labor- atory of the U. S. Geological Survey: TABLE 27. ANALYSES OF SELMA LIMESTONE FROM KEMPER COUNTY. (W. S. McNeil, Analyst.) 1 2 3 Silica (Si0 2 ) 16.48 10.60 20.00 Alumina (A1 2 0 3 ) \ 6 . 97 5 . 90 8.92 Iron oxide (Fe 2 0 3 ) J Lime carbonate (CaC0 8 ) 74.34 82.47 68.91 Magnesium carbonate (MgCOs) .67 Tr. Tr. Water .67 .82 1.06 1. Two and one-half miles east of Scooba. 2. Seven miles east of Sucarnochee. 3. One and one-half miles south of Wahalak. ♦Bull. 283, U. S. Geol. Survey, p. 216. fBull. 243, U. S. Geological Survey, pp. 206 to 219. 69.10 | 17.10 1.60 .72 9.18 54 CEMENT MATERIALS. AVAILABLE CLAYS IN AND ADJACENT TO THE SELMA AREA. As above stated, a mixture of clay with a pure limestone is neces- sary in the manufacture of Portland cement. The amount of clay varies with the amount of lime carbonate in the limestone. A pure limestone like that from Prairie Rock (see page 52) requires about one part of clay to two parts of limestone, while the limestone from near Wahalak requires the addition of a purer limestone. There are two possible sources of clay for Portland cement in the Selma area and adjacent to it. These are (a) residual Selma clays; {b) Porter’s Creek clay. Residual Selma Clays. Highly plastic clays, resulting from the decomposition of the Selma limestone, occur to greater or less extent over the entire Selma area. Where disintegration is complete the residual Selma clays are low in lime carbonate and comparatively high in alumina and silica. In the absence of any other clays they may be used with the limestones in making cement. In fact, the Alabama Portland cement plant at Demopolis, Alabama, uses the residual clay which occurs along Tombigbee River. The limestone used at this plant is comparatively low in lime carbonate and, therefore, requires only a small amount of clay to reduce the lime to the proper percentage. TABLE 28. ANALYSES OF SELMA LIMESTONE USED AT THE ALABAMA PORT- LAND CEMENT PLANT, DEMOPOLIS, ALABAMA. 1 2 Silica (Si0 2 ) 12.50 9.88 Alumina (Al,Oa).. 1 Iron oxide (Fe 2 03 ) J Lime carbonate (CaCO*) 80.71 77.12 Magnesium carbonate (MgO) 1.05 1.08 Sulphur trioxide (SOj) 1.62 n. d. Water 1.36 5.72 1. R. S. Hodges, analyst. 2. Sen. Doc. No. 19, 58th Congress, 1st Session, p. 22. No analysis of the clay used at the above mentioned plant is available. The following is an analysis of the residual Selma clay from Uniontown, Alabama: porter’s creek clay. 55 TABLE 29. ANALYSIS OF RESIDUAL CLAY FROM UNIONTOWN, ALABAMA. (R. S. Hodges, Analyst.) Silica (Si0 2 ) 69.57 Alumina (A1 2 0 3 ) \ 1Q Iron oxide (Fe 2 0 3 ) / Lime (CaO) 0.37 Ignition 9.68 TABLE 30. ANALYSES OF RESIDUAL SELMA CLAYS FROM MISSISSIPPI. 1 2 3 4 5 6 7 Silica (Si0 2 ) 63.63 75.95 72.32 65.30 56.97 63.35 67.60 Alumina (A1 2 0 3 ) 10.34 9.62 8.74 12.63 15.09 13.70 12.55 Iron oxide (Fe 2 0 3 ) 8.25 5.08 7.44 12.18 10.40 7.90 7.60 Lime (CaO) 3.75 1.25 1.55 1.50 1.00 0.80 .80 Magnesia (MgO) .50 .74 .47 .63 0.54 0.60 .78 Volatile matter (C0 2 ) 7.77 2.52 5.58 2.27 10.90 6.50 5.00 Sulphur trioxide (S0 3 ) 34 .34 .51 0.25 0.34 0.34 .17 Moisture 4.25 3.50 3.45 4.75 2.95 6.02 5.50 1. West Point. 2. West Point. 3. West Point. 4. Starkville. 5. Agricultural College. 6. Agricultural College. 7. Agricultural College. Porter's Creek Clay. Immediately above the Selma limestone, south of Houston, the Porter’s Creek clay outcrops in a belt 2 to 15 miles wide. North of Houston the Ripley and Clayton limestones intervene between the Selma and the Porter’s Creek formations. It is known as the “Flat- woods” country, and in places is characterized by low flat land resembling the broad bottom of a large river. The Porter’s Creek clay is a dark gray clay which has a tendency to break into rectangular blocks when exposed to the sun. It contains small flakes of mica, which in places have been segregated into small dikes. Excellent exposures of the Porter’s Creek formation occur through- out the State where the Lafayette has been removed. The Mobile, Jackson and Kansas City Railway has made deep cuts into the clay at Walnut, Ripley, and along the divide between Houston and Maben. The Southern Railway, from West Point to Winona, cuts into the Porter’s Creek in the hills between Maben and Pheba. A sample of the residual Porter’s Creek from 1 mile west of Stark- ville was analyzed with the following results: 56 CEMENT MATERIALS. TABLE 31. ANALYSIS OF RESIDUAL PORTER’S CREEK CLAY, FROM 1 MILE WEST OF STARKVILLE. Silica (Si0 2 ) 75.60 Alumina (AI2O3) 7.00 Iron oxide (FejOj) 8.24 Lime (CaO) 1.20 Magnesia (MgO) .67 Volatile matter (CO 2 ) 3.91 Sulphur trioxide (SO 3 ) .25 Moisture... 2.97 The following analyses of the Porter’s Creek clays were made from different localities in the State: TABLE 32. ANALYSES OF PORTER’S CREEK CLAY. Silica, (Si0 2 ) Alumina (Al 2 03 ).».- • • Iron oxide (Fe 20 j). . . . Lime (CaO) Magnesia (MgO) Volatile matter (C0 2 ). . Sulphur trioxide (SOs). Moisture 1 2 3 57.25 71.47 61.62 6.17 9.45" 8.87 18.95 6.97 16.29 1.05 .40 .91 .95 .63 .69 7.75 5.04 7.77 .21 .13 .28 7.59 5.65 4.50 1 . Residual clay from near Macon. 2. Residual clay from Wahalak. 3. Porter’s Creek clay from Winston County. The Illinois Central Railway from Starkville to Ackerman crosses the Porter’s Creek formation, showing deep cuts of laminated grayish clay. Again, on the Mobile and Ohio Railway, between Scooba and Lauderdale, occurs the same characteristic clay which has been traced across Alabama, Mississippi, western Tennessee and Kentucky. A sample of the Porter’s Creek clay from the town of Scooba was analyzed in the laboratory of the U. S. Geological Survey* with the following results: TABLE 33. ANALYSIS OF PORTER’S CREEK CLAY FROM SCOOBA. (W. S. McNeil, Analyst.) Silica (SiO z ) 61.92 Alumina (AI 2 O 3 ) 19.47 Iron oxide (Fe20s) 2.81 Magnesia (MgO) 1.98 Soda (Na 2 0) 50 Loss on ignition .' 12.29 ♦Geology and Mineral Resources of Miss., U. S. Geol. Survey, Bull. No. 283, p. 55. JACKSON FORMATION. 57 It will be seen from the above analyses that the Porter’s Creek clay is an excellent quality of clay for use in making cement. JACKSON FORMATION. Heretofore no attention has ever been paid to the calcareous marls of the Jackson formation for Portland cement. During the course of the present survey, experiments have been made using the marl for cement. Samples were collected from two of the most important places where the marl comes to the surface, and analyzed. The formation was so called from the typical exposures in the bank of Pearl River at Jackson. It underlies a large area of central Missis- sippi, just north of the Vicksburg limestone area. It comprises what is known as the “central prairie” region. The marl outcrops in com- paratively few places owing to the overlying surface formations and residual soil. The surface of the country is not so broken as the region to the north and also to the south. The materials composing the formation are principally calcareous, clayey marls, and unconsolidated limestones, clays and sands. The sandy portion is confined to about the uppermost 50 feet of the for- mation. The remaining 300 feet are marls and clays. The marls are easily recognized by the great amount of shells which they contain. Throughout the entire Jackson area where the marls are near the surface they have undergone a chemical change. In the two analyses of Table 34a the nature of the change is apparent. No. 1 is an analysis of a partly weathered Jackson marl; No. 2 is the analysis of the clay derived from the marl. There has been a loss of lime carbonate in the marl and a porportionate gain of silicon dioxide and aluminum oxide in the clay. These changes have been brought about by weathering. The weathering of the marl, therefore, accounts for the presence of the green plastic clay which is found over the entire Jack- son area from which the overlying Lafayette and yellow loam have been removed. DISTRIBUTION. Yazoo City . — Perhaps the best exposure of the Jackson calcareous marls in the State is found in the bluff at Yazoo City. This formation is exposed in the bluff for a distance of about 10 to 12 miles north and 15 miles south of the city. The following is a section of the bluff at the city reservoir: 58 CEMENT MATERIALS. Section of the Bluff at Yazoo City. Feet Yellow loam brick clay 10-12 Gray calcareous Loess, which stands in perpendicular walls 100 Lafayette pebbles 12 Jackson marls, containing Zeuglodon bones and other Jackson fossils \ 180 A sample of the marl taken from this place was analyzed with the following results: TABLE 34, ANALYSIS OF JACKSON MARL-CLAY, YAZOO CITY Silica (Si0 2 ) Alumina (AI 2 O 3 ) Iron oxide (FejOj) Lime (CaO) Magnesia (MgO) Volatile matter (C0 2 ) Moisture 40.90 13.50 5.55 14.62 .88 19.25 The above analysis w r as made from the surface and represents the transitional stage between the more highly calcareous marl and the plastic residual clay. Jackson . — The Jackson marls are exposed in the bank of Pearl River between the wagon bridge and the Alabama and Vicksburg Rail- road bridge. A continuation of the exposure is found extending up Town Creek. Other exposures are found in the bed of Moody’s Branch near the city waterworks’ stand-pipe, and in the railway cut J mile north of the Asylum station. The Jackson clays, underlain by calcareous marls, are found in the deep cut on the Illinois Central Railway 1 mile south of Jackson. At the latter place the marl weathers to a slightly pinkish clay, which possesses a jointed structure. The clay contains in places small patches of very fine sand. The quality of the unweathered marl and the clay from this place is shown in the following analyses: TABLE 34a. ANALYSES OF JACKSON MARL AND CLAY 1 MILE SOUTH OF JACKSON. 1 2 Silica (Si0 2 ) 35.72 59.82 Alumina (A1 2 0 3 ) 13.79 12.24 Iron oxide (Fe 2 0 3 ) 5.38 6.10 Lime (CaO) 17.00 2.90 Magnesium oxide (MgO) 1.99 1.68 Sulphur trioxide (SO 3 ) 0.12 2.11 Volatile matter (C0 2 ) 17.91 7.55 Moisture 5.85 6.08 VICKSBURG FORMATION. 59 VICKSBURG FORMATION. The Vicksburg formation outcrops in a narrow belt of territory in Mississippi from 1 to 12 miles wide, extending across the State in an approximately northwest, southeast direction. The accompanying geological map of the State shows the area underlain by the Vicksburg and its relation to the Jackson marls on the north and the Grand Gulf group on the south. The Vicksburg and the Jackson in Mississippi are mapped as two distinct formations, while in Alabama they are described together under the term St. Steven’s limestone. The Vicksburg is the equiva- lent of the upper, and the Jackson of the lower part of the St. Steven’s limestone. The character and composition of the St. Steven’s limestone has been described by Dr. E. A. Smith in Bulletin No. 243, pp. 77-81, U. S. Geological Survey. The large number of analyses of this lime- stone made in the laboratory of the Alabama Survey shows that it is well adapted to the manufacture of Portland cement. It carries from 75 to 95 per cent of calcium carbonate, with very little magnesium carbonate. In Mississippi the Vicksburg formation includes thin beds of fine grained non-magnesium limestone from 1 to 4 feet thick, alternating with highly calcareous marl beds more or less indurated in places and bearing a rich fauna of Oligocene age. Some of the ledges of limestone make excellent building stone and lime, but owing to the great amount of interbedded marl and surface material, quarrying Jthe limestone has been found to be unprofitable. The alternating nature of the limestone and marl is shown in the following section of the bluff at Vicksburg,* between the city and the National Cemetery: Section of the Bluff in Vicksburg. Inches 22. First stratum of limestone from top, overlain by Loess. 10 21. Gray to yellowish marl 9 20. Heavy-bedded limestone 46 19. Indurated marl 34 18. Thin, calcareous, plastic clay 2 17. Indurated marl 6 16. Clay similar to No. 10 2 15. Indurated marl 5 ♦Bull. 283, U. S. Geol. Survey, p. 38. 60 CEMENT MATERIALS. Section of the Bluff in Vicksburg — Continued. Inches 14. Clay 4 13. Hard limestone 18 12. Clay and marl from $ to 2 inches thick 15 11. Indurated marl 21 10. Limestone 18 9. Gray marl 18 8. Limestone 18 7. Marl 3-6 6. Hard limestones 52 5. Marl : 6 4. Limestone 27 3. Marl 17 2. Limestone 20 1. Marl 45 In the above section there are 17 feet and 5 inches of hard lime- stone, and 16 feet and 8 inches of marl and clay. The impractica- bility of using the hard limestone without using the marl and the clay is at once apparent. One of the special features in the study of this formation has been to determine the possibility of utilizing the marls in combination with the limestone in the manufacture of Portland cement. A large number of analyses of the marls from different localities show that they contain no large amounts of injurious properties, and can be used for cement as they come from the quarry. The marls and the clays supply t,he silica and alumina for Portland cement and are therefore of equal value to the limestone. In fact, by taking a general average of the analyses of the limestones and the interbedded marls we obtain the desired mixture for a Portland cement, without the addition of other materials. In the central and the eastern parts of the State the Vicksburg formation is more homogeneous than it is in the western area. In Smith County the Vicksburg is a soft porous limestone which is known as the “chimney rock.” It is quarried for chimneys and foundation pillars by sawing it into any desired shape with a large saw. On exposure to the air it hardens and lasts for 30 to 40 years. The “chim- ney rock” is one of the purest forms of the Vicksburg limestone. DISTRIBUTION. Vicksburg . — The typical locality of the Vicksburg formation is in the bluff in and near the city of Vicksburg. In the bluff overlooking Plate III, BLUFF AT VICKSBURG SHOWING VICKSBURG LIMESTONE. (Photo by W. N. Logan.) VICKSBURG FORMATION. 61 the Mississippi River just below the oil mill, J mile south of the con- fluence of the Yazoo and the Mississippi rivers, the following exposure of the Vicksburg formation was observed. The limestone outcrops on the river for a distance of 800 feet. On the slope facing the river between the oil mill and the city the limestone underlies a thin veneer of soil. It is exposed in the branches and in a few places along the track of the Yazoo and Mississippi Valley Railway from the oil mill to the National Cemetery. The top of the Vicksburg forms a bench-like terrace which extends back to the foot of the Loess bluff. Section of Vicksburg Limestone at the Oil Mill , 2\ Miles South of Vicksburg. Feet 9. Loess in the bluff back from the river 100 8. Marl 2 7. Ledge of hard limestone 3 6. Bed of soft marl 3 5. Ledge of limestone 5 4. Marl stratum 5 3. Ledge of hard limestone 5 2. Hard limestone 3 1. Bed of compact marl 5 Water’s edge. The thickness of the exposure in the above section is about one- third of the entire thickness of the Vicksburg formation. Analysis of each stratum from Nos. 1 to 7 inclusive was made with the following results. The numbers of the analyses correspond to the numbers in the above section. TABLE 35. ANALYSES OF VICKSBURG LIMESTONE AND MARLS FROM VICKSBURG. 1 2 3 4 5 6 7 Average 8 Silica (Si0 2 ) 32.45 6.43 7.39 25.27 5.58 13.62 3.10 13.41 7.08 Alumina (A1 2 0 3 ) 2.12 .31 1.02 4.50 1.00 3.00 .25 1.74 .61 Iron oxide (Fe 2 0 3 ) 2.05 2.00 2.48 5.37 2.18 2.75 1.62 2.63 2.50 Lime (CaO) 34.20 50.25 47.50 29.50 49.97 40.37 50.63 43.20 50.44 Volatile matter (C0 2 ) 26.65 39.00 38.65 24.10 39.26 33.66 41.00 34.62 37.22 Magnesium oxide (MgO). . .38 1.36 1.45 1.99 1.01 1.72 .99 1.29 1.07 Sulphur trioxide (SO3) 08 .36 .51 2.76 .30 .98 .60 .79 0.38 Moisture 1.60 .61 1.10 3.95 .82 2.75 .60 1.63 0.40 No. 8 is a limestone from Steel’s Bayou, Vicksburg. A small fragment of limestone from each ledge including Nos. 2, 3, 5 and 7 was pulverized and the mixture analyzed with the results given in No. 1 below. A similar analysis was made from a mixture of the marls with the results given in No. 2. 62 CEMENT MATERIALS. TABLE 36. ANALYSES OF VICKSBURG LIMESTONE AND MARLS FROM VICKSBURG. (Dr. A. M. Muckenfuss, Analyst.) 1 2 Average Silica (Si 02 ) . 4.95 24.97 14.96 Alumina (Al 2 Os) 56 6.49) 5.46 Iron oxide (Fe 20 j) 2.47 1.36/ Lime (CaO) 50.11 . 33.97 42.04 Carbon dioxide (CO 2 ) 39.30 26.38 32.84 Magnesia (MgO) 1.13 1.60 1.37 Alkali (K 2 0) 0.15 0.70 .43 Sulphuric acid (SOs) 0.25 1.00 .63 Phosphoric acid (P 2 O 5 ) 0.03 0.07 .06 Insoluble matter, volatile (organic) 0.84 2.24 1.54 Moisture 0.20 0.82 .51 The value of the Vicksburg limestone as a Portland cement rock is shown by comparing the general average of the above analyses to the analyses of actual cement mixtures given in the following table. The amount of combined impurities in the Vicksburg limestone is smaller than that in the actual mixtures given below : TABLE 37. COMPOSITION OF ACTUAL MIXES USED IN AMERICAN CEMENT PLANTS Silica (Si 02 ) Alumina (AI2O3) Iron oxide (Fe 203 ). . . Lime (CaO) Magnesia (MgO) Carbon dioxide (CO 2 ) Water 4.35 14.77 12.85 15.18 (4.92 L 1 .21 43.03 42.76 42.97 1.74 1.02 n.d. 35.61 34.71 n.d. n.d. n.d. n.d. 6.42 8.2 6.56 n.d. 7.20 6.00' 11.8 13.52 13.46 13.85 12.62 14.94 12.92 2.66 4.83 1.10 1.77 41.8 42.07 41.25 41.40 42.26 42.34 42.30 0.8 2.07 n.d. n.d. 2.67 2.21 2.08 n.d. 35.31 n.d. n.d. 34.86 36.42 fn 10 35.68 35.49 d. n.d. n.d. The Vicksburg outcrops at intervals in the bluff from the city of Vicksburg to the town of Redwood or beyond; the limestone occurs beneath a thick Lafayette and Loess overburden which attains a maximum thickness of about 175 feet. In the hills south of Vicksburg the Grand Gulf clays are found on the hillsides and in the bluffs beneath the Loess and Lafayette. In places it is a highly plastic gray clay interbedded with aluminous sandstone. From five miles south of Vicksburg, on the old Roche land, a sample of Grand Gulf clay was analyzed with the following results* : ANALYSIS OF CLAY 5 MILES SOUTH OF VICKSBURG. Silica (SiOa) 58.50 Altunina (AI 2 O 3 ) 19.04 Ferric oxide (Fe 2 Os) 1.93 Lime (CaO) 1.48 Magnesia (MgO) 1.66 Sulphur trioxide (SO3) Trace Moisture 3.19 Loss on ignition 8.26 ♦Bull. 283, U. S. Geol. Survey, p. 68 Plate IV. LEDGE OF VICKSBURG LIMESTONE, CLINTON. VICKSBURG FORMATION. 63 Byram . — The Vicksburg formation outcrops in the hills northwest of Byram. One mile north of the station the rock is exposed in the railway cut. From the little hill to the west of this exposure the hard limestone was used formerly for making lime. Hard ledges of limestone interbedded with beds of indurated marl are exposed in the banks of Pearl River from about J of a mile below to miles above Byram. In places the same ledge may be seen in the bank of the river only a few feet above the water for a distance of J mile. There is a gentle fold in the rocks with the axis extending in an approximately east and west direction (see Plate V). Samples of the limestone and marl from the bank of the river at Byram were analyzed with the following results: TABLE 38. ANALYSES OF VICKSBURG LIMESTONE AND MARL FROM BYRAM. Silica (Si02) Alumina (AI2O3) Ferric oxide (Fe 203 ). .. Lime (CaO) Magnesia (MgO) Volatile matter (C0 2 ). Sulphur trioxide (SO 3 ) Moisture Limestone Mafl 2.28 26.42 2.42 8.25 2.19 5.20 50.55 27.77 1.40 1.44 40.87 26.00 .30 2.00 .31 3.00 About 2\ miles north of Byram on the east bank of Pearl Rive r the following section is exposed: Section of Vicksburg Formation 2\ Miles North of Byram* Inches Gray rotten limestone containing grains of glauconitic sand 24 Harder gray limestone 24 Indurated brown marl 24 Hard, compact, gray limestone 16 Soft yellow marl 14 Very hard gray limestone 10 Gray marly clay 8 Compact limestone 20 Indurated white to gray marl 20 Ferruginated sandy limestone 72 Green-sand marl base of exposure 60 Plain . — The Vicksburg limestone outcrops in the first cut south o^ Plain, on the Gulf and Ship Island Railway. The exposure here as at ♦Unpublished notes obtained by the writer while employed on the U. S. Geol. Survey. 64 CEMENT MATERIALS. Vicksburg is composed of alternating beds of limestone and marl. At the top of the formation is a plastic, calcareous red clay, which is formed from the decomposition of the limestone and the marl. Samples of each stratum in the cut were analyzed with the following results : TABLE 39. ANALYSES OF VICKSBURG LIMESTONE AND MARLS FROM NEAR PLAIN. Average Silica (Si0 2 ) 7.57 Alumina (A1 2 0 3 ) 1.23 Iron oxide (Fe 2 0*) 5.50 Lime oxide (CaO) 46.33 Magnesium oxide (MgO) 0.02 Volatile matter (C0 2 ) 38.54 Sulphur trioxide (SO*) 09 Moisture 27 1.85 4.95 12.52 14.11 17.53 9.76 1.37 0.00 4.75 2.87 1.42 1.94 1.75 4.25 5.50 6.60 15.15 6.46 52.12 47.50 39.75 39.78 29.87 42.56 0.49 1.16 0.81 0.40 0.02 .48 41.87 39.25 34.50 34.33 27.45 35.99 25 17 17 .25 1.25 1.56 1.62 5.25 1.70 The Vicksburg limestone can be easily traced by the outcrops in the hills from the exposure in the railway cut south of Plain westward to Pearl River, and eastward to Brandon. At no place is there a great thickness exposed, rarely more than 20 feet, -and frequently much less. Brandon . — The Vicksburg limestone is exposed at the railway station at Brandon and for J mile to the west. Another exposure is found at the old Yost lime kiln site, 1 mile east of the station. The most complete exposure of the Vicksburg, east of Pearl River, is found at the old Robinson quarry, about 4 miles southeast of Brandon. The formation is made up of hard ledges of crystalline limestone alternating with beds of calcareous marl of about equal thickness. This rock was quarried for some time by a firm in Jackson. It was crushed and used in the foundation of the new State Capitol. Work was discontinued because of the great amount of useless marl which had to be removed to get the rock. The analyses as given below show that the marl and limestone could all be used in making Portland cement. This material is easily quarried as there is little or no superincum- bent matter. A spur from the main line of the Alabama and Vicksburg Railway has been built from Rankin to the quarry, thus giving an easy outlet for the material. Plate VICKSBURG LIMESTONE ON PEARL RIVER, BYRAM. VICKSBURG FORMATION. 65 TABLE .40. ANALYSES OF VICKSBURG LIMESTONE FROM ROBINSON QUARRY, 4 MILES SOUTHEAST OF BRANDON. Silica (Si0 2 ) 4.22 4.55 5.56 1.58 16.88 Alumina (A1 2 0 3 ) 75 .00 1.09 4.40 5.70 Iron oxide (Fe 2 0 3 ) 4.37 4.25 4.01 3.31 3.59 Lime oxide (CaO) 49.62 49.92 48.44 48.40 36.86 Magnesium oxide (MgO) 09 .09 .78 1.27 .99 Volatile matter (C0 2 ) 40.05 39.61 38.12 39.70 33.16 Sulphur trioxide (S0 3 ) .36 .72 .24 .45 v .24 Moisture 88 .95 1.61 .60 2.10 Bay Spring . — There are numerous outcrops of the Vicksburg for- mation between Brandon and Bay Spring, but as they are so far removed from lines of transportation it is hardly possible that the limestone will soon become of value for cement, and consequently only one of the most important outcrops will be described in this report. On. the east side of Tallahala Creek, about 4 miles west of Bay Spring, the Vicksburg limestone outcrops in the road and on the side of the hill. Above the limestone is a pink, plastic clay very similar to the clay overlying the limestone 1J miles south of Plain (see pre- ceding page). The thickness of the Vicksburg here is 65 feet. The uppermost member of the Vicksburg is a ledge of hard bluish gray limestone, which is so much more resistant than the overlying Grand Gulf clay that it forms a marked bench along the hillside at this place. One thing noticeable about the Vicksburg limestone at this locality is the absence of marl beds alternating with harder ledges of limestone. The top of the formation is capped with a hard ledge of limestone, but all the material underneath this to the bottom of the hill is a soft, porous, white to yellowish limestone. The harder ledges of limestone were formerly used for burning lime. On Mr. Houston’s land, 2 miles west of Sylvarina, is a quarry where the soft, porous limestone is sawed out for building chimneys. The rock for 3 to 4 feet below the surface has disintegrated into a rotten mass, easily picked to pieces with a spade. Below this it is sufficiently compact to be used for building chimneys. The quarry has been worked for 17 years. Chimneys built of this rock first disintegrate at the top. The rock is very porous; it fills with water which freezes in the winter and causes it to break. The rock has also been used for making lime and 5 66 CEMENT MATERIALS. doubtless is very desirable for this purpose, since it is almost pure lime carbonate. No detailed work has been done on the Vicksburg limestone by the present survey along the New Orleans and Northeastern, and the Mobile and Ohio railways. The hard upper ledges outcrop in the hills north and east of the town of Vossburg. Two samples of limestone from near Nancy, Clarke County, were collected by W. N. Logan, and analyzed with the following result: TABLE 41. ANALYSES OF VICKSBURG LIMESTONE FROM NEAR NANCY, CLARKE COUNTY. Silica (Si0 2 ) Alumina (A1 2 Oj) Iron oxide (Fe 2 03 ) Lime oxide (CaO) Magnesia (MgO) Volatile matter (C0 2 ) . Sulphur trioxide (SO3) Moisture 7.31 6.77 13.61 4.68 4.00 2.00 36.62 45.51 .29 .64 35.20 35.40 2.78 3.00 1.00 1.79 “Near Red Hill,* in Wayne County, on Limestone Creek, the Mobile and Ohio Railway is cut through a considerable hill, where the limestone group of the Eocene formation is well exhibited. Lime- stone Creek, which runs south of the cut on the railroad and empties about 400 yards from it, into the Chickasawhay River, contains large ledges of hard, compact limestone; and southeast of the cut about l£ miles the sandstone which appears south of the cut and not well cemented, crops out as a hard limestone, an excellent material for building purposes.” At the confluence of Limestone Creek and Chickasawhay River Dr. Harper gives the following section of the limestone: Section of Vicksburg Limestone at the Mouth of Limestone Creek, Wayne County. Surface soil, chiefly sand — Yellowish limestone — Calcareous sand containing Pecten — Calcareous marl containing Orbitoides, Ostrea, Pecten, Area, Flabellum, Cardita, etc — Shell marl — No thicknesses are given. Three analyses of the limestone from Red Hill, Wayne County, are given by Dr. L. Harper (f) as follows: ♦Geology and Agriculture of Mississippi, 1857, L. Harper, p. 140. tlbid, p. 166. Plate VI. VICKSBURG LIMESTONE, ROBINSON QUARRY, NEAR RANKIN. (Photo by W. N. Logan.) VICKSBURG FORMATION. 67 TABLE 42. ANALYSES OF VICKSBURG LIMESTONE FROM RED HILL, WAYNE Silica (Si02) COUNTY. (Dr. L. Harper, Analyst.) 6.30 15.05 9.20 Alumina (AI2O3) | 7.20 5.35 6.65 Iron oxide (Fe203) Lime (CaO) 48.44 44.58 47.12 Carbon dioxide (CO2) . . >38.06 35.02 37.03 Water n. d. n. d. Dr. E. W. Hilgard (*), in speaking of the occurrence of the Vicks- burg limestone in Wayne County, says: “On the Chickasawhay , between Red Bluff and the latitude of Waynesboro, both marls and limestones crop out with frequency; the same is the case on the creeks on the east side as on Cakchey’s Mill Creek and Limestone Creek, especially near the mouth of the latter, at the foot of the hill on which Dr. E. A. Miller lives — the most southerly outcrop of the calcareous Vicksburg on the Chickasawhay. The sections exhibited here in the river banks and cuts of the railroad correspond so closely to those between Yost’s lime kiln and Brandon depot that the spec- imens can hardly be distinguished from each other when placed side by side, the only difference being the great abundance of Orbitoides in the soft white marl intervening between the strata of rock. The ledges of hard limestone (in Wayne County) are not so well defined — the rock being softer and whitish.” (*)Geology of Mississippi, Hilgard 1860, p. 146 68 CEMENT MATERIALS. ADVANTAGEOUS LOCATIONS FOR CEMENT PLANTS. To build a Portland cement plant at a point remote from trans- portation lines is to invite financial loss. And under the present system of levying freight rates it is almost equally perilous to build a plant where there is but one transportation outlet, unless satis- factory arrangements have been made previous to the erection of the plant. In Mississippi there are four general localities where raw materials, and good transportation facilities can be obtained. TISHOMINGO COUNTY. The Southern Railway from Memphis to Chattanooga passes near the northern outcrop of the oolitic limestone in Tishomingo County near where the road crosses Bear Creek. At this point it is only 8 miles to the Tennessee River. The largest boats of that river run as far as the mouth of Bear Creek. A cement plant built at this point would have an outlet to the north by boat and a railway con- nection to the east, west and south. Coal could be obtained by river or from the nearby Alabama fields at a minimum cost. A Portland cement plant at Mingo bridge could use the oolitic limestone and the overlying shale. Bear Creek furnishes sufficient water to run a mill by water power. The newly constructed line of the Illinois Central Railway connecting Birmingham, Alabama, and Jackson, Tennessee, with an outlet to the north and south, runs within 3 miles of this place. STARKVILLE AND WEST POINT. The Selma limestone and Porter’s Creek clay are in proximity along the Mobile and Ohio Railway in Kemper County, along the Illinois Central in Oktibbeha County, and along the Southern in southern Clay County. The relations of these locations to transpor- tation lines are clearly indicated on the map. The Mobile and Ohio furnishes an outlet to the north and south. The Southern line from LOCATIONS FOR PLANTS. 69 Greenville, Mississippi, to Birmingham, Alabama, offers an outlet to the east and west. The Aberdeen branch of the Illinois Central connects with the main line from Louisville to New Orleans at Durant, thus giving an outlet into a new territory. Starkville and West Point offer exceptional advantages for Port- land cement plants, inasmuch as limestone and clay are found near in great abundance, and the coal field of Alabama is less than 100 miles away. In fact either of these places is closer to the coal field by rail than the Alabama Portland Cement plant at Demopolis. With a bed of limestone 800 to 1,000 feet thick underlying Nox- ubee. Clay, Lee, eastern Oktibbeha and Chickasaw counties, and an inexhaustible supply of clay just west of the Selma area, there is a sufficient amount of raw material to supply the Portland cement trade of the entire United States for an indefinite length of time. Starkville and West Point afford good advantages in regard to proximity of raw material and fuel for a cement plant; and they have a fair outlet for the finished product. COLUMBUS. The town of Columbus has plenty of limestone near and has some advantages over West Point and Starkville in being closer to the coal field of Alabama. With the opening of the Tombigbee River to navigation cheaper rates could be had than at any other city in east- ern Mississippi. Good clays can be obtained in the Tuscaloosa and the Eutaw formations in the hills east of Tombigbee River. JACKSON AND VICINITY. The Vicksburg limestone outcrops in the banks of Pearl River at Bryam, in the railway cut 1J miles south of Plain, and again at the Robinson quarry near Rankin. All of these outcrops are on railway lines and within a radius of 14 miles from Jackson. The limestones at all of these places have been analyzed and found to be desirable materials for Portland cement. Jackson is a good distributing point with seven railway lines radiating to the north, east, south and west. Two railway lines, the Illinois Central and the Gulf and Ship Island, connect Jackson with deep water routes to the Gulf. 70 CEMENT MATERIALS. VICKSBURG. Vicksburg offers more natural advantages for the location of a cement plant than any other city in the State. Raw material of limestone and marl are found in the bluffs facing the river. The Mississippi River and the Yazoo and Mississippi Valley Railway afford transportation to the north and south; the Alabama and Vicksburg Railway affords transportation to the east and west. Coal could be obtained by river from Pittsburg, by the Yazoo and Mississippi Valley Railway from Illinois and western Kentucky, and by the Alabama and Vicksburg Railway from the Alabama coal field. INDEX, PAGE PAGE Ackerman 56 Cement, Parian 16 Acknowledgments 10 1 Portland 19 Advantageous locations for Puzzolam 18,19 plants 68 Cement industry in the south . 11, Alabama 35, 41, 42, 46, 54, 55, 12, 15 56, 59, 68-70 , in the U. S 12 Alcorn Co 24 Chalk 23 Alkali waste 25,26 Chickasaw 24, 48, 69 Analysis of alkali waste 26 Chickasawhay River. . . . 66,67 , cement 20 Clarke Co 66 , cement materials, 18, 22, 24, 25, 54 Classification of cements 16 , clays 40, 53, 55, 56, 58 Clay Co .24, 48, 68, 69 , kiln coals 33 Clays 27,40, 53, 55, 56, 58 , lignites 35 Coal 32,33 , limestones 38, 39, 47, 49, Columbus 49, 69 50-54, 61-67 Complex cement 17 , marls 61-64 Composition of P. cement 20 oyster shells 25 Condition of C. industry j in U.S. 12 > slag 26 Contents 4 Argillaceous limestone . . 21 Coonewah Creek 47 Artesia ...... 49 Corinth 43,44 Aspdin, Joseph 12 Cost of crushing, drying, etc. . 33 Available clays 54 Cost of drying 30 Cretaceous formation . . . . . . .27, 38, 40 Baldwin 46 Crawford 52,53 Bay Spring 65 Cypress Pond 38,39 Bear Creek . . . .38, 39, 68 Biloxi 10,25 Danville 45 Bodea Creek 53 Demopolis, Ala 54 Booneville 45 Devonian . . . .37, 38, 40 Brandon 64, 65, 67 Dry process 29 Britton, J. B 40 Brooks, J. B 52 Early history of P. cement. ... 12 Brown, Calvin 10,34 Eckel, E. C 10, 16, 18, 19, Burning 32 22, 23, , 26, 27, 33, 36 By ram 63,69 Edison plant _ 30 Eutaw 41,46,69 Cakchey’s Mill Creek _ . . 67 Carbonate Cement 16 Flatwoods 55 Carboniferous 38-40 Fresh-water marl 24 Cements, carbonate . . . . 16 Fuels 32-35 classification of . . . . 16 Fulton 40 complex 17 hydrate 16 General geology 36 Keene’s 16 Geological commission . . 2 Natural 17 Geological corps 2 72 INDEX. PAGE Geology 36-67 Grand Gulf 62, 65 Greenville 69 Grinding raw material 28 Grinding the clinker 35 Guntown 46 Hand, W. F 10,38,40,51 Harper, L 66 Hilgard, E. W 38, 40, 48, 67 . History of P. cement 12 Hodges, R. S 54, 55 Houston 55 Hydrate cements 16 Hydraulic properties 18 Illinois 35 Illustrations, list of 9 Index 71 Indiana 38 Introduction 11 Itawamba Co 49 Iuka 39,40 Jackson 57; 58, 69 Jackson formation 57, 59 J umperto wn 45 PAGE Maben 55 Macon 50-53, 56 Macon Creek 51 McNeil, W. S 51,53,56 Magnesia 18,23 Map after page 74 Marls 24,61-64 Methods of manufacture 28 Mingo 38, 39, 68 Mississippi River 61, 70 Mitchell, D.L 10 Monroe Co 24, 49, 50 Nancy.... „ 66 Natural gas 34 New Jersey 21 Noxubee Co 24, 50, 69 Noxubee River 48, 51-53 Object of this report 12 Oil as fuel 34 Okolona 48, 49 Oktibbeha Co 24, 42, 49, 50, 68, 69 Old Town Creek., 46 Osborn 50 Output of P. cement in U. S. .. . 13,14 Oyster shells 25 Keene’s cement 16 Kemper Co 50, 68 Kentucky 35, 38, 56, 70 Lafayette formation 38, 39, 42, 43, 45-49, 55, 57, 58, 62 Lauderdale 56 Lee Co 45,47,49,69 Lehigh district 21, 22 Letter of transmittal 3 Limestone 21, 22, 24, 29, 38, 47, 49-54, 59-66 Limestone Creek 66 List of illustrations 9 List of tables 7 Loess. 59, 61, 62 Logan, William N 10, 47, 50, 66 Lowndes Co 24, 50, 52 Panama canal 15 Parian cement 16 Pearl River 57, 58, 63,69 Pennsylvania 21,34 Pheba 55 Plain 63-65, 69 Plaster of Paris. . . . 16 Pontotoc 4r Pontotoc Co 47 Pontotoc Ridge 48 Porter’s Creek clay 43, 53-57, 68 Portland cement, imported .... 11 Portland cement material of Miss 36 Post oak land 42 Potter’s clay 40 Prairie rock 52,54 INDEX. 73 PAGE Prairie soil 42,49 Preparing raw material 28, 29 Preparing slag for cement 31 Producer gas 34 Production of cement in U. S. . 14 Puzzolan cement 18, 19 Rankin 64, 69 Raw materials 21 Red Bluff 67- Redwood 62 Red Hill 66,67 Residual Selma clays 54 Retarder 36 Rienzi . . . 45 Ripley 55 Ripley formation 53,55 Rotary dryer 29, 30 Rotten limestone. See Selma Chalk. Scooba 51, 53, 56 Selma chalk 24, 40-53, 68, 69 Shale 27 Short P. O 37 Shuqualak 53 Slag 26 Slate 28 Smith Co 60 Smith, Eugene A 59 South, cement industry in 11, 15 Specific gravity of P. cement. . . 18, 20 Stanger and Blount 35 Starkville 49, 50, 55, 56, 68, 69 State capitol 64 Sucamochee 53 Sylvarina .' . 65 PAGE Tallahatta Creek 65 Tchouticabouff River 25 Tertiary formation 27 Temperature for burning 19 Tennessee 42, 44, 56, 68 Tennessee River 37, 68 Thickness of Selma chalk 42 Thrasher 45 Tibby Creek 48 Tishomingo Co 29, 37, 39, 40, 68 Tombigbee River .41, 46, 48, 49, 52, 69 Town Creek 58 Tupelo 45,47,49 Tuscaloosa clays 40 Tuscumbia River 43, 45 Verona 47, 48 Vicksburg 59-62, 64, 70 Vicksburg formation 57, 59-67, 69 Vossburg 66 Wahalak 53,56 Walnut 55 Wayne Co 66,67 Waynesboro 67 Well records 48 Wenasoga 44 West Point 49, 55, 68, 69 West Virginia 34 Wet process 31 Wheeler 46 Whetstone 37 Winona 55 Winston Co 56 Table of contents 4 Tables, list of 7 Yazoo City 57, 58 Yazoo River 61 Yellow Creek 37 Mississippi State Geological Survey ALBERT F. CRIDER, DIRECTOR. BULLETIN NO 2 CLAYS OF MISSISSIPPI PART I. Brick Clays and Clay Industry of Northern Mississippi By WILLIAM N. LOGAN i s L, m— m— ♦♦♦« BRANOON-NASHVILLE STATE GEOLOGICAL COMMISSION. His Excellency, James K. Vardaman Governor Dunbar Rowland Director of Archives and History A. A. Kincannon Chancellor of the State University J. C. Hardy President Agricultural and Mechanical College Joe N. Powers State Superintendent of Education GEOLOGICAL CORPS. Albert F. Crider Dr. William N. Logan Dr. Calvin S. Brown. . • Director Assistant Geologist Assistard Geologist LETTER OF TRANSMITTAL. State Geological Survey. Jackson, Mississippi, July 20, 1907. To Governor James K. Vardaman , Chairman , and Members of the. Geological Commission: Gentlemen — I submit herewith a report on the clays and clay industry of northern Mississippi by Dr. William N. Logan, and respect- fully recommend its publication. Very respectfully, Albert F. Crider, Director. TABLE OF CONTENTS. PAGE Letter of transmittal 3 List of illustrations 16 List of tables 19 CHAPTER I. , ORIGIN AND CLASSIFICATION OF CLAY. Position and relation of clay to other earth materials 23 Lithosphere 23 Regolith 23 Durolith 23 Rocks of the regolith 24 Sand 24 Clay 24 Loess 24 Marl 24 Peat 25 Gravel, pebbles and bowlders 25 Rocks of the durolith 25 ' Sandstone 25 Conglomerate 25 Shale 26 Limestone 26 Marble 26 Granite 26 Classification of rocks 27 Composition of the lithosphere 28 Rock alteration and decomposition 30 Origin of clay 32 Residual clay 33 Transported clay 35 Classification of clays 36 CONTENTS. 5 Position and relation of clay to other earth materials — Continued. Lithosphere — Continued. page Uses of clay 39 Brick clays 39 Common brick 39 Vitrified brick 39 Fire brick 40 Tile clay 40 Flue clay 40 Stoneware clay 40 Earthenware clay 40 China clay 40 Cement clay 40 Ballast clay 40 Paper clay 40 Fuller’s earth 40 Adulterant clays 40 Terra cotta clay 40 Miscellaneous clays 40 Occurrence of clays 41 CHAPTER II. CHEMICAL PROPERTIES OF CLAY. Chemical elements of clay 43 Chemical compounds of ultimate analysis 46 Silica 47 Alumina 47 Iron oxide 48 Calcium oxide 48 Magnesia 49 Alkalies 49 Minerals in clays 50 Kaolinite 50 Silica 51 Iron 52 Limonite 52 Hematite 53 6 CONTENTS. Minerals in clays — Continued. Iron — Continued. page Siderite 53 Pyrite 54 Marcasite 54 Ilmenite 54 Gypsum 55 Calcite 56 Feldspar 57 Mica 58 Hornblende 58 CHAPTER III. PHYSICAL PROPERTIES OF CLAY. Structure 61 Shrinkage 62 Air shrinkage 62 Fire shrinkage 64 Specific gravity 65 Color 65 Hardness 66 Feel 67 Odor 67 Taste 67 Slaking 67 Plasticity 68 Factors of plasticity 69 Fusibility 70 Mechanical analysis 75 Bonding power 77 Tensile strength 77 Porosity 81 CHAPTER IV. PROCESSES OF CLAY MANUFACTURE. Mining 83 Pick and shovel method 83 CONTENTS. 7 Mining — Continued. page Plow and scraper method 84 Steam shovel method 84 Transportation 85 Wheelbarrow haulage 85 Cart haulage 85 Wagon haulage 85 Scraper haulage 86 Car haulage 86 Selection of timber for tracks 86 Grinding 89 Crushers 89 Rolls 89 Granulators 89 Disintegrators 90 Reduction mills 92 Dry pans 92 Ball mills 92 Screening 93 Rotary screen 93 Inclined stationary screen 94 Inclined vibratory screen 94 Revolving screen 95 Tempering 95 Soak pit 95 Ring pit 95 Pug mill 96 Wet pan 97 Molding 97 Soft-mud process 99 Hand molding 99 Machine molding 99 Stiff-mud process 102 Plunger type machine 102 Auger type machine 102 Repressing brick 105 Dry press process 107 8 CONTENTS. PAGE Drying 109 Principles of drying 109 Methods of drying brick 117 Open yard dryer 117 Rack and pallet dryer 117 Shed dryer 118 Artificial dryers 118 Burning 119 Types of kilns 120 Up-draft kiln 121 Scove kiln 121 Dutch or clamp kiln 121 Down-draft kilns 122 Beehive kiln 122 Rectangular kiln 122 Continuous kilns 122 CHAPTER V. FUEL. Classes of fuels 124 Wood 124 Coal 125 Varieties of coal 125 Peat 125 Lignite 125 Bituminous coal 126 Anthracite 126 Determination of the calorific value of coals . 126 Mississippi lignites 129 Oil 130 Gas 131 CHAPTER VI. PROPERTIES OF BRICK. Early history of brick 133 Brick tests 133 CONTENTS. 9 Brick tests — Continued. page Crushing strength 134 Absorption 134 Impact strength 136 Rattler test 136 Tensile strength 137 Transverse strength 137 Weight of brick 138 Size of brick 138 Number of brick in construction work 141 Varieties of brick in a kiln 141 CHAPTER VII. IMPERFECTIONS OF BRICK. Defects of form 143 Swollen brick 143 Warped brick 144 Cracked brick 144 Defects of color 145 Light color in red burning brick 145 Efflorescence 146 Kiln white 146 Wall white 147 Defects of structure 150 Laminations 150 Granulations 150 Serrations 151 Brittleness 151 CHAPTER VIII. GEOLOGY OF MISSISSIPPI CLAYS. Paleozoic 153 Devonian 153 Sub-Carboniferous (Mississippian) 154 Mesozoic 155 Cretaceous 155 10 CONTENTS. Mesozoic — Continued. » Cretaceous — Continued. page Tuscaloosa 155 Eutaw (Tombigbee) 157 Selma chalk (rotten limestone) 158 Ripley 159 Cenozoic 160 Tertiary 160 Eocene 160 Midway 160 Wilcox (Lagrange) 160 Claiborne 161 Tallahatta buhrstone 161 Lisbon and undifferentiated Claiborne 161 Jackson 162 Oligocene 163 Vicksburg 163 Miocene 164 Grand Gulf 164 Quaternary 165 Lafayette 165 Natchez 167 Loess 167 Columbia 167 Recent deposits 168 CHAPTER IX. THE CLAYS AND CLAY INDUSTRIES OF NORTHERN MISSISSIPPI BY COUNTIES. Alcorn County 169 Geology 169 Clay industry 170 Corinth 170 Rienzi 171 Attala County 172 Geology 172 CONTENTS. 11 Attala County — Continued. page Clay industry 172 Kosciusko 172 Carroll County 173 Geology 173 Clay County 175 Geology 175 Clay industry 175 West Point 175 Chickasaw County 180 Geology 180 Clay industry 180 Okolona 180 Houston 181 New Houlka 181 Choctaw County 182 Geology 182 Coahoma County 183 Geology 183 Clay industry 183 Clarksdale 183 DeSoto County 186 Geology 186 Clay industry 186 Lake View 186 Hernando 188 Grenada County 188 Geology 188 Clay industry 189 Grenada 189 Holcomb 191 Hinds County 191 Geology 191 Clay industry 191 Jackson 191 Holmes County 193 Geology 193 12 CONTENTS. Holmes County — Continued. page Clay industry : 193 Lexington 193 Durant 196 Kemper County 197 Geology 197 Clay industry 197 Wahalak 197 Lafayette County 197 Geology 197 Clay industry 198 College Hill Station 198 Lauderdale County 199 Geology 199 Clay industry 199 Lockhart 199 Meridian 200 Lee County 200 Geology 200 Clay industry 201 Baldwin 201 Saltillo 202 Verona 202 Nettleton 203 Leflore County 203 Geology 203 Clay industry 203 Greenwood 203 Minter City 204 Lowndes County 205 Geology 205 Clay industry 205 Columbus 205 Madison County 206 Geology 206 Clay industry 206 Canton 206 CONTENTS. 13 PAGE Marshall County 207 Geology 207 Clay industry 208 Holly Springs 208 Montgomery County 210 Geology 210 Clay industry 210 Winona 210 Monroe County 211 Geology 211 Clay industry 211 Aberdeen 211 Amory 212 Newton County 214 Geology 214 Clay industry 214 Newton 214 Noxubee County 215 Geology 215 Clay industry 215 Macon 215 Oktibbeha County 218 Geology 218 Clay industry 218 Starkville 218 Agricultural College. . . 220 Maben 222 Panola County 223 Geology 223 Clay industry 223 Sardis 223 Batesville 224 Pontotoc County 225 Geology 225 Clay industry 225 Pontotoc 225 Prentiss County 226 Geology 226 14 CONTENTS. Prentiss County — Continued. page Clay industry 226 Boone ville 226 Thrasher 227 Rankin County 227 Geology 227 Clay industry 227 Brandon 227 Rankin State Farm 229 Scott County 230 Geology 230 Clay industry ' 230 Forest 230 Morton 231 Sunflower County 232 Geology 232 Clay industry 232 Indianola 232 Moorhead 234 Tate County 234 Geology 234 Clay industry 234 Senatobia 234 Tippah County 235 Geology 235 Clay industry 235 Ripley 235 Tunica County 236 Geology 236 Clay industry 236 Robinsonville 236 Union County 237 Geology 237 Clay industry 237 New Albany 237 Warren County 239 Geology 239 CONTENTS. 15 Warren County — Continued. page Clay industry 240 Vicksburg 240 Washington County 242 Geology 242 Clay industry 242 Elizabeth 242 Greenville 242 Hampton 243 Webster County 244 Geology 244 Winston County 244 Geology 244 Clay industry 245 Louisville 245 Yalobusha County 245 Geology 245 Clay industry 245 Water Valley 245 Yazoo County 246 Geology 246 Clay industry 247 Yazoo City 247 Directory of Mississippi Clay Workers 248 Acknowledgments 250 Index 251 LIST OF ILLUSTRATIONS. PLATE opp. page I. Mantle rock resting on bed rock, Vicksburg 22 II. Roadbed in the Loess, Natchez 24 III. A — Brickettes for tensile strength test. 62 B — Electric furnace for testing clays 62 IV. Stiff-mud brick machine of the auger type 68 V. Either-side rocker dump car 70 VI. Swivel-dumping clay car 72 VII. Conical corrugated clay crusher 74 VIII. Horizontal granulator 76 IX. Reduction mill 78 X. Dry pan 80 XI. Stiff-mud brick machine, end cut 84 XII. Rotary clay screen of the octagon form 86 XIII. Pug mill 88 XIV. Wet pan 96 XV. Soft-mud brick machine and pug mill 98 XVI. Clay disintegrator 108 XVII. Rotary automatic brick cutter 110 XVIII. Steam-power double-mold brick repress 112 XIX. A — Open-yard system of drying, Holly Springs 118 B- — Hand molding, and starting a scove kiln, Holly Springs 118 XX. A* — Setting brick in a scove kiln, Starkville 120 B — Shed dryer, brick hacked on ground 120 XXI. A — Burned brick in scove kiln, good burn 122 B — Over-burn in scove kiln, bottom brick slaggy 122 XXII. Eutaw sands on Tombigbee River, Columbus 156 XXIII. A — Denudation in Lafayette after deforesting, Brandon 164 B — Soft-mud brick hacked under covered shed 164 XXIV. Sodding Loess slopes with Bermuda grass as a pro- tection against erosion, National Park, Vicks- burg 166 LIST OF ILLUSTRATIONS. 17 PLATE OPP. PAGE XXV. Outcrop of Buhrstone shale-clay, Vaiden 170 XXVI. A — Quartz bowlders of the Buhrstone, Near West. . . 172 B — Erosion in the Lafayette. Vaiden 172 XXVII. Up -draft clamp kilns, end view, West Point 174 XXVIII. Taking brick from off-bearing belt of an end-cut machine 176 XXIX. A — Power house of the Bullard brick plant, Jackson 192 B — Clay pit of the Bullard brick plant, Jackson 192 XXX. A — Power house of the Love brick plant, Durant 196 B — Up-draft clamp kilns, Durant 196 XXXI. Public building at Durant built of Mississippi pressed brick 198 XXXII. A — Brown loam and Lafayette overlying the Jack- son, Canton clay pit 204 B — Stratified Lafayette with talus, railroad cut, Newton 204 XXXIII. Allison clay pit, Holly Springs 206 XXXIV. A — Typical erosion in Columbia loam, State Exper- iment Farm, Holly Springs 208 B — Lafayette overlying Wilcox, Holly Springs 208 XXXV. A — Clay partings in the Lafayette sands, Newton. . .214 B — Erosion in the Lafayette sands by underground water, Newton 214 XXXVII. A — Resistant layer in the Columbia loam, Brandon . 226 B — Lafayette sands, Brandon 226 XXXVIII. A — Terrace in the Loess at the National Cemetery, Vicksburg 228 B — Vicksburg limestone, near Brandon 228 XXXIX. A — Lignitic stratum in the Jackson sands, Morton. . 230 B — Local fault in the Jackson strata, Morton 230 XL. A — Vicksburg limestone, Vicksburg, distant view. . . 238 B — Vicksburg limestone, Vicksburg, near view 238 XLI. Erosion in Brown loam and Loess, National Park, Vicksburg 240 XLI I. Typical Loess topography, Vicksburg 242 18 LIST OF ILLUSTRATIONS. PAGE Figure 1. Brickette mold 78 2. Outline of brickette 79 3. Side-dumping clay car 87 4. Double-friction hoisting drum 88 5. Clay disintegrator 90 6. Pebble cylinder machine 91 7. Horse-power soft-mud brick machine 98 8. Brick mold sanding machine 100 9. Automatic continuous rotary brick cutter 103 10. Hand -power repress brick machine 106 11. Six-mold dry press brick machine 107 12. Steel-rack car for transporting brick on palettes 115 13. Section of the Lafayette, Lexington 194 14. Cross bedding in the Lafayette, Lexington . 195 LIST OF TABLES. P'AGE 1. Composition of the lithosphere 29 2. Loss of constituent minerals in the decomposition of crystal- line rocks 34 3. Loss of constituent minerals in the decomposition of lime- stone 34 4. Chemical components of clay 43 5. Analyses of sojne Mississippi clays 44 6. Aluminous minerals found in kaolin 51 7. Chemical composition of feldspars (Dana) 57 8. Effect of coal and cinder dilution on the tensile strength of raw and burned clays 63 9. Shrinkage in Mississippi clays 64 10. Composition and fusing points of seger cones 72 11. Methods of grouping in mechanical analysis 75 12. Mechanical analyses of Mississippi clays 77 13. Tensile strength of Mississippi brick clays 80 14. Durability of different woods 87 15. Crushing machinery used in Mississippi brick plants 93 16. Summary of tempering machinery used in Mississippi brick plants 97 17. Methods of molding Mississippi brick 108 18. Number of grains of saturated water vapor in a cubic foot at various temperatures 110 19. Calorific value of different fuels 123 20. Calorific value of Alabama coals 129 21. Composition of Mississippi lignites 129 22. Amount and cost of petroleum for boiler fuel 130 23. Composition of fuel gases 132 24. Fuel value of gases 132 25. Absorption tests of Mississippi bricks 135 26. Size of some Mississippi bricks 139 27. Analysis of tripoli from the sub-carboniferous near Eastport 154 28. Analysis of Eastport limestone 154 20 LIST OF TA'BLES. PAGE 29. Analysis of Cypress Pond limestone 155 30. Analysis of Mingo shale 155 31. Analysis of ocherous clay from the Tuscaloosa, six miles north of Iuka 156 32. Analysis of clay from Penniwinkle Hill 156 33. Analyses of Tuscaloosa clays from Tishomingo County 157 34. Analyses of Selma chalk 158 35. Analysis of Ripley sandstone 159 36. Analysis of clay, Ripley 159 37. Analyses of Flatwoods clays 160 38. Analysis of Wilcox clay, Grenada 161 39. Analyses of Wilcox pottery clays 161 40. Analysis of Barnett clay 163 41. Analyses of Vicksburg limestone 163 42. Analyses of Grand Gulf clay stones 164 43. Analyses of Grand Gulf clays 165 44. Analysis of residual Selma clay, Corinth 170 45. Analysis of Selma limestone, Corinth 171 46. Analysis of residual clay, Vaiden 174 47. Analysis of residual clay, Vaiden 174 48. Analyses of Selma limestone and residual clay, West Point . . 175 49. Analysis of surface clay, West Point 177 50. Analysis of clay used at the Welch-Trotter brick plant, West Point 178 51. Analyses of clays, West Point 178 52. Analysis of surface clay, West Point 179 53. Analysis of Selma limestone, Okolona 180 54. Analysis Selma chalk, Okolona 181 55. Analysis of brick clay, New Houlka 182 56. Cost of building 300 feet of road with burned clay ballast, Clarksdale 184 57. Analyses of clays used by the Clarksdale Brick and Tile Co., Clarksdale 184 58. Analysis of buckshot clay used at the Rheinhart Brick and Tile Factory, Clarksdale 185 59. Analysis of clay, Lake View 187 60. Analysis of alluvial clay, Lake View 188 LIST OF TABLES. 21 PAGE 61. Analyses of Columbia clay, Grenada 189 62. Record of artesian well at the Bledsoe Brick yard, Grenada . 190 63. Analysis of shale-clay, Grenada 190 64. Analysis of brick clay, Jackson 191 65. Analysis of brick clay, Jackson 192 66. Analysis of Columbia clay, Lexington 196 67. Analyses of clays from the Wilcox, Lafayette County 198 68. Analysis of Wilcox stoneware clay, Lockhart 199 69. Analysis of Wilcox clay, Lockhart 200 70. Analysis of brick clay, Meridian 200 71. Analysis of clay used by the Baldwyn Brick and Tile Co., Baldwyn 201 72. Analyses of clays, Greenwood 204 73. Analyses of alluvial clays, Minter City 205 74. Analyses of clays, Canton 207 75. Analysis of fire clay, Holly Springs 208 76. Analyses of stoneware clays, Holly Springs 209 77. Analysis of brick clay, Holly Springs 210 78. Analysis of joint clay, Aberdeen 212 79. Analysis of yellow loam clay, Amory 213 80. Analyses of clays, Newton 215 81. Analyses of Selma limestones, Macon 216 82. Analysis of residual Selma clay, Macon 216 83. Analysis of clay, Macon 217 84. Analyses of limestone and clay Starkville 218 85. Analyses of Selma limestone and overlying clay, Starkville... 219 86. Analyses of limestone and clays, Agricultural College 220 87. Analyses of limestone and clays, Agricultural College 222 88. Analysis of white clay, Maben 222 89. Analysis of. Columbia clay, Sardis 224 90. Analysis of unweathered Loess, Batesville 224 91. Analysis of Columbia clay, Pontotoc 225 92. Analysis of Columbia clay, Brandon 228 93. Analysis of Columbia clay, Brandon 229 94. Analysis of clay, Rankin County State Farm 229 95. Analyses of clays, Forest 230 96. Analysis of Jackson clay, Morton 231 97. Analysis of alluvial clay, Indianola 232 22 LIST OF TABLES. PAGE 98. Analyses of brick clays, Indianola 233 99. Analysis of buckshot clay, Moorhead 234 100. Analysis of brick clay, Ripley 236 101. Analysis of Lafayette clay, New Albany 237 102. Analysis of brick clay, New Albany 238 103. Analysis of brick clay, New Albany 238 104. Analysis of Lafayette clay, New Albany 239 105. Analysis of clay, Elizabeth 242 106. Analysis of alluvial clay, Greenville 243 107. Analysis of pottery clay, near Webster 244 108. Analysis of surface brick clay, Yazoo City 247 109. Directory of Mississippi clay workers 248 Plate MANTLE ROCK RESTING ON BED ROCK, VICKSBURG. ALL ROCK ABOVE ROADBED IS MANTLE ROCK, CHAPTER I ORIGIN AND CLASSIFICATION OF CLAY. POSITION AND RELATION OF CLAY TO OTHER EARTH MATERIALS. Structurally the known and knowable portion of the earth may be divided into three great spherical envelopes. An outer gaseous sphere, the atmosphere; a liquid sphere, the water sphere or hydro- sphere; and a solid rock sphere called the lithosphere. LITHOSPHERE. The lithosphere consists of a loose mantle of earthy material, the regolith, at the surface and a more compact, indurated sub- stratum, the durolith, to which the term “bed rock” is often applied. Regolith. The regolith consists of unconsolidated beds of sand, gravel, pebbles, bowlders and clay, or of mixtures of these together with organic matter forming loams, marls, peat, and soils. The regolith varies in thickness from a few inches to several hundred feet. It is often but the residual product resulting from the weathering of the bed rock. Its thickness, therefore, may represent the amount of bed-rock decay that has taken place at that point or it may represent the amount of decay which has taken place on some neighboring higher area, the debris of which has been transported to this point. Durolith. The durolith consists of beds of consolidated and more or less indurated rocks such as shale, sandstone, limestone, coal, granite and marble. In some regions the durolith is completely concealed by the regolith so that it may be studied only by means of deep cuts and the records of wells which pierce its strata. As to the thickness of the durolith we have little knowledge. The most profound excava- tions of Nature do not descend to depths much greater than one mile. The deepest excavations or borings made by man transcend this limit only by a small degree. Therefore, our knowledge of the thick- ness of the crust of the earth, as well as our knowledge of its internal mass, we gain only by inference. 24 CLAYS OF MISSISSIPPI. Rocks of the Regolith, The mantle rocks are unconsolidated fragments of rock waste and organic decay forming sand, clay, marl, loess, and gravels. Sand . — Sand is composed of hard particles, usually of quartz, though sands of feldspar, magnetite, mica, gypsum and other minerals are not uncommon. Most quartzose sands contain at least small quantities of some of these minerals. The individual grains of sand may have sharp edges and irregular forms. These are generally particles which have not been eroded by transportation. Sharp sands are for the most part residual sands. Transported sands are more regular in form and have a rounded surface, or sub-angular edges. The size of the sand particles are extremely variable. They range from the coarseness of gravel to the impalpability of dust. In color there exists a multiplicity of tints and shades. In some sands the coloring matter is inherent; in many, however, it is due to the pres- ence of an enclosing film of pigment such as oxide of iron. Clay . — Clay is a soft rock which is usually smooth or greasy to the touch. When mixed with the proper proportion of water it may be readily molded into desired forms which will have the power of retaining their shape. This property, plasticity, is not possessed in a high degree by other rocks and is therefore one of the deter- minative characters of clay. Clay is a mechanical mixture of min- erals. The proportion of these mineral constituents may vary; hence the composition of clays varies greatly. Aluminous clays are those containing a large quantity of the mineral kaolinite, which is the basis of all clays. Arenaceous clays contain a large quantity of sand. Calcareous clays contain much carbonate of lime. Ferru- ginous clays are those containing considerable proportion of some iron compound. Loess . — Loess is a silty material composed of very fine particles of clay, sand, limestone and other earthy materials and also some organic matter. In cuts and excavations it tends to maintain verti- cal faces and a columnar structure. In many places it contains irregular concretions of calcium carbonate and the shells of species of gastropods. Marl . — Marl is a mixture of clay, sand, and limy material. Shell marl is admixture of clay, sand and the shells and bones of animals, such as snails, mussels, fish and oysters. Marls may be of marine Plate II. ROADBED IN THE LOESS, NATCHEZ, ORIGIN AND CLASSIFICATION OF CLAY. 25 origin formed under sea water or they may be of lacustrine origin, formed in lakes. Peat .- — Peat is a dark substance composed mainly of vegetable matter which has undergone changes under water. It is formed by the accumulation of vegetable matter in lakes, ponds and marshes. Its amount of organic matter depends inversely upon the amount of earthy matter deposited with the vegetation. Gravel, Pebbles and Bowlders. — Gravel, pebbles and bowlders are fragments of hard rocks of sizes varying from a pea in gravel and pebbles, to rounded fragments several feet in diameter in bowlders. Since this material can be transported only by streams of high velocity, these deposits are usually found where such streams suddenly lose their velocity. Mountain streams which descend to plains deposit such rocks. G, ? Rocks of the Durolith. The rocks of the durolith are more compact than those of the regolith. They may exist without planes of division or they may be formed of layers; in the former case they are said to be massive, in the latter to be stratified. Sandstone, shale, limestone, conglomerate, coal, granite, gneiss, marble and slate are some of the more common kinds of bed-rock. Sandstone .— Sandstone is a rock formed of grains of sand bound together by some cementing substance. The ' cement may be iron, lime or silica. Coarse sandstones are composed of large sand grains. Where the grains are small the texture of the rock is fine. Sand- stones may be massive or stratified. Crossbedded sandstones are those in which the bedding planes do not lie in parallel lines, but in which one set of planes lies oblique to another set. The color of sand- stones is usually dependent on the presence of films of coloring matter coating the individual grains. Conglomerate . — Conglomerate is formed by the cementation of gravel and pebbles. As in the case of sandstone, the cement may be iron, lime or silica. If the pebbles are rounded, the rock is called pudding stone; if the fragments are irregular or angular, the rock is called breccia. Such rocks may be deposited under the sea, in which case they may be identified as marine in origin by the organic remains usually found in them. Many beds of such rocks devoid of organic 26 CLAYS OF MISSISSIPPI. remains are supposed to have been deposited in lodgement areas upon the land. Shale . — Shale is compressed clay which has a form of cleavage causing it to split into flakes or blocks. Its physical properties are similar to those of clay, though it is usually harder and more dense. Shale is formed of clay which has been carried by the action of streams from the land and deposited either in the sea or in lakes. After deposition the clay is subjected to the pressure of overlying rocks, and to crustal movements which increase its density and develop its structure. Since the clay particles are smaller and lighter than other rock fragments, they are carried further out. The sorting action may result in beds of marked purity. The color of shales is generally dark or blue and is due to the presence of either some iron compound or of organic matter. The removal of the coloring matter by weather- ing usually results in lighter colors. Limestone . — Limestone is composed, for the most part, of calcium carbonate derived from the skeletons of animals. All marine animals secreting either an endo-skeleton or an exo-skeleton may contribute to the formation of such beds. Deposits of coral form one of the chief sources of such lime material. Skeletons of shell -fish dropped within the littoral zone of the sea become broken and the fragments cemented together to form shell rock which by further changes may form compact limestones. Shells of animals of microscopic size form beds of chalk, sometimes of great extent and thickness. Marble .— Marble is a metamorphic limestone of crystalline nature. Slate may have been formed likewise from the metamorphism of shale. Granite .— Granite is a crystalline rock of igneous origin. It is composed mainly of varying amounts of feldspar, mica, quartz and hornblende, with very much smaller amounts of other minerals. The crystals are usually of microscopic size and closely interlocked. The color of the granite is largely dependent on the feldspar, which is usually either pink or gray. The disintegration and the decomposi- tion of granite result in the formation of beds of sand and kaolin, the former being derived from the quartz and the latter from the feldspar. Wherever granite under the influence of metamorphic action has become foliated, it forms a rock termed gneiss. ORIGIN AND CLASSIFICATION OF CLAYS. 27 Rocks are usually classed as: (1) fragmental rocks, those formed from the particles of older rocks; (2) igneous rocks, those formed from the cooling of molten magmas; (3) metamorphic rocks, those which have undergone alteration under the influence of heat and pressure. Fragmental rocks, which are deposited under water, are called aqueous or sedimentary. Those deposited by wind are called eolian rocks. Limestone, sandstone and shale are common examples of fragmental rocks; granite, syenite and gabbro are examples of igneous rocks; while marble, slate and anthracite coal are examples of meta- morphic rocks. Classification of Rocks. I. Fragmental rocks, also called aqueous or sedimentary, deposited by winds, water and ice on land and in water. A. Sand group. 1. Sand. 2. Gravel. 3. Sandstone. 4. Pudding-stone. 5. Breccia. B. Lime group. 1. Chalk. 2. Coquina. 3. Limestone. 4. Dolomite. 5. Marl. 6. Travertine. 7. Tufa. C. Clay group. 1. Kaolin. 2. Clay. 3. Shale. 4. Loam. 5. Loess. 6. Till. 28 CLAYS OF MISSISSIPPI. II. Igneous rocks, resulting from the solidification of molten magmas. A. Pyroclastic rocks. 1. Volcanic ash. 2. Lapilli and bombs. 3. Tuffs. 4. Scoriae. 5. Pumice. 6. Puzzolana. B. Lavas or glassy rock. 1. Acidic. a. Obsidian. b. Perlite. c. Trachyte. d. Rhyolite. 2. Basic. a. Basalts. b. Dolerite. C. Phanerocrystalline rocks. 1. Acidic. a. Granite. b. Syenite. 2. Basic. a. Gabbros. b. Peridotites. III. Metamorphic rocks., A. Rocks of sedimentary origin. 1. Marble. 2. Slate. 3. Quartzite. B . Rocks of igneous origin. 1. Gneiss. 2. Schist. Composition of the Lithosphere. The rocks of the lithosphere are composed of a large number of minerals, these minerals in turn being composed of elements. To ORIGIN AND CLASSIFICATION OF CLAY. 29 illustrate, calcite (CaC0 3 ), the principal constituent of limestone, is composed of three elements, calcium, carbon and oxygen. These are united in- the proportion of one part calcium and one part carbon to three parts of oxygen. More than 70 chemical elements have been discovered in the earth. Eight of these elements form nearly 99 per cent of the solid crust of the earth. The estimated composition of the solid portion of the lithosphere is given by F. W. Clarke* as follows: TABLE I. COMPOSITION OF THE LITHOSPHERE. Element Symbol 1 . Oxygen (O) . . 2. Silicon (Si) . . 3. Aluminum (Al) . . 4. Iron (Fe). 5. Calcium (Ca). 6. Magnesium (Mg). 7. Sodium (Na). 8. Potassium (K) . . 9. Titanium (Ti) . . 10. Hydrogen (H) . . 11. Carbon (C)... 12. Phosphorus (P) . . 13. Manganese (Mn) . 14. Sulphur (S)... 15. Barium (Ba) . 16. Strontium (Sr) . . 17. Chromium (Cr) . . 18. Nickel (Ni) 7. 19. Lithium (Li) . . 20. Chlorine (Cl).. 21. Fluorine (FI).. Per Cent in Crust .... 47.02 . . . 28.06 8.16 4.64 . . . . 3.50 . . . . 2.62 . . . . 2.63 2.32 41 17 12 09 07 07 05 02 01 01 01 01 01 Total 100.00 The last thirteen of these elements comprise only 1.05 per cent of the solid crust, while the precious metals such as gold and silver, and the baser metals such as copper, lead and zinc, constitute such a small percentage of the rocks as to be considered negligible quantities. As already stated the elements are united to form minerals which make up the rocks of the lithosphere. Oxygen uniting with silicon produces an oxide (Si0 2 ) which acts as an acid. The acid uniting with bases such as aluminum, potassium and calcium forms silicates, and uniting with other elements it forms oxides of iron, calcium, ♦Analysis of Rocks, Bui. 168, U, S. Geol. Survey, 1900, p. 15. 30 CLAYS OP MISSISSIPPI. magnesium, etc. These by the union with acids produce sulphates, chlorides, carbonates and other combinations. Rock Alteration and Decomposition. The disintegration of rocks is brought about by the action of two sets of forces. The internal dynamical forces of the earth produced by the loss of heat and consequent shrinkage of the 1 earth, result in faulting, folding, oscillation and deformation, accompanied by vulcanism and earthquakes. These movements disrupt the rocks and contribute to their decay. The forces of the atmosphere, the hydrosphere and the life sphere are agents of destruction. Air which contains nitric acid, carbon dioxide, oxygen and watery vapor is an active agent of rock decay. Fresh faces of rocks soon lose their brightness and freshness under the corroding effect of the atmosphere. Sudden changes of temperature set up strains in rocks which they are not able to withstand and consequently they are broken up, and their fragments exposed to other weathering agents. The wind catching up particles of rocky material blows them with violent force against the surfaces of rocks and wears them away. Water running over the surface of rocks wears them by means of the rock particles which it carries with it. Falling water beats upon and erodes the surface of soft rock. Waves erode the rocks on the shores, breaking them apart and using the fragments as tools for further destruction. Water also exerts a chemical action on rocks. Some rocks may be dissolved by pure water but others are soluble only in waters containing acids. Limestones which yield readily to the action of acid-bearing waters are dissolved and carried away in large quantities by surface and underground waters which contain acids derived from decom- posing mineral and organic matter. Caverns, sink-holes, and under- ground streams and passages which represent the dissolved and eroded portions of limestone beds are generally characteristic of limestone regions. Carbon dioxide formed by plant decay and collected from the atmosphere by falling water is one of the most important solvents. In the presence of moisture oxygen becomes an effective agent of rock decay. Compounds of iron in the rocks, are attacked by oxygen and decomposed, thus contributing to the decay of the rock. ORIGIN AND CLASSIFICATION OF CLAY. 31 The process of oxidation may be accompanied by the process of hydration, in which case the oxidized mineral takes up water. Hydra- tion usually produces a softer mineral, one more easily eroded and thus weakens the rock. Roots of trees growing in crevices exert a mechanical action which splits the rocks apart, and a chemical action which dissolves them by virtue of vegetable acid from the roots. Man by digging wells, excavating tunnels and cultivating the soil also breaks up the rocks. The decomposition and the alteration of rocks containing silicates of aluminum is the source of clay. The group of silicates known as feldspars constitutes the most fruitful source of clay. Feldspar is one of the principal constituents of granite and other igneous or met- amorphic rocks of the granitoid group. For this reason the forma- tion of residual deposits of clay is closely associated with the disin- tegration of granite and the subsequent alteration of its silicate min- erals. The disintegration and decomposition of granite is accomplished by the various mechanical and chemical agents which are actively engaged in rock weathering. The alteration of the silicates is accom- plished by the action of mineral and vegetable acids carried through the pores of the rock by circulating waters. One of the most destructive of these acids is carbonic acid(H 2 C0 3 ). This acid first attacks the potash and soda, hence silicates containing these bases are the first to be broken up. Lime and magnesia com- pounds are next attacked, then the silicates containing iron, and lastly the aluminum silicates, the most stable of the compounds. These complex compounds having been broken up into their com- ponent elements, reactions between the elements occur and new com- pounds are formed. Aluminum uniting with silicic acid forms new silicates which are free from the other bases, and, since they are more readily soluble, are carried away by circulating waters. The aluminum silicates thus formed are kaolinite, cimolite, hal- loysite, collyrite, schrbtterite, etc.; also some oxides or hydroxides of alumina, such as gibbsite. These aluminous minerals form beds of rock called kaolin. Kaolin is the basis of all clays. The purity of a clay depends upon the percentage of kaolin which it contains. The higher the percentage of kaolin the purer the clay. 32 CLAYS OF MISSISSIPPI. The other minerals which are usually associated with kaolin in clays are quartz, calcite, hematite, siderite, limonite, pyrite, feldspar, mica, rutile, lignite and dolomite. The kind and the quantity of these mineral impurities affect greatly the usefulness of the clay. The impurities may have originated from the decomposition of the rock which formed the clay, or they may have been deposited with the clay during a process of transportation and deposition, or they may have been deposited in the clay by circulating waters. The quantity of kaolin present and the amount and nature of the impurities serve as a guide to the uses for which clay may be employed, but the phys- ical properties of the clay must also be considered. Origin of Clay. The origin of kaolin has been suggested in the foregoing pages. We have now to consider the origin of the various deposits of clay which are found in the rocks of the lithosphere. The following out- line suggests a method of classification of clay deposits according to their origin: I. Residual clay. A. Clays derived from igneous rocks. a. Kaolin derived from granite and other feldspathic rocks. b. Ferruginous and impure kaolin derived ordinarily from igneous rocks containing hornblende and other ferro- magnesian minerals. B. Clays derived from metamorphic rock. a. Kaolin derived from gneiss and from other feldspathic metamorphic rocks. b. Impure kaolin or clay derived from slate, schist or argillaceous marbles. C. Clays derived from sedimentary rocks. a. Surface clay derived from shale. b. Surface clay derived from argillaceous limestone. c. Surface clay derived from argillaceous sandstone. ORIGIN AND CLASSIFICATION OF CLAY. 33 II. Transported clays. A. Fluvatile clays, those transported by streams. a. Delta clays, those deposited in deltas. b. Estuary clays, those deposited in the broad mouths of rivers. c. Flood-plain clays, those deposited on the flood plain of rivers. B. Lacustrine clays, transported and deposited in lakes. C. Marine clays, transported and deposited in marine waters- a. Unconsolidated beds of clay. b. Shales, compact laminated clays. D. Glacial clays, those transported by ice. a. Till. b. Loess (in part). E. Eolian clays, transported by winds. a. Loess (in part). b. Adobe clays. Residual Clay. — Residual clays are beds of kaolin or the more common varieties of clay formed in place by the decomposition of other rocks. As has already been stated the disintegration of the rocks is brought about by weathering. The alteration of the con- stituent minerals is accomplished by acids carried by meteoric waters. The depth to which kaolinization may take place is necessarily lim- ited to a thin outer zone of lithosphere. Very rarely such deposits are of greater thickness than 100 feet, and the greater majority would fall within the limit of a fourth of that thickness. In exceptional cases kaolinization is thought to be produced by ascending solutions. Under such conditions the deposits may extend to depths greater than those produced by the action of surficial agents. The following table, compiled from Merrill's Rocks, Rock Weather- ing and Soils, pp. 215-17, illustrates the loss of constituent minerals which crystalline rocks may suffer during decomposition: 34 CLAYS OF MISSISSIPPI. TABLE 2. LOSS OF CONSTITUENT MINERALS IN THE DECOMPOSITION OF CRYSTALLINE ROCKS. Gneiss Phonolite Syenite Decom- Decom- Constituent Fresh posed Fresh posed Fresh Decomposed Silica (Si0 2 ) 60.69 45.31 55.67 55.72 59.70 58.50 46.27 Alumina (A1 2 0 3 ) 16.89 26.55 20.64 22.19 18.85 25.71 38.57 Iron oxide (Fe 2 0 3 ) ... . 9.06 12.18 3.14 3.44 4.85 3.74 1.36 Lime (CaO) 4.44 Trace 1.40 1.28 1.34 .44 .34 Magnesia (MgO) 1.06 . 89 . 42 . 44 . 68 Trace .25 Potash (K 2 0) 4.25 2.40 5.56 6.26 5.97 1.96 .23 Soda (Na 2 0) 2.82 1.10 7.12 2.65 6.29 1.37 . 37 Phosphoric acid (P 2 Os) .25 . 47 Ignition 62 13.75 4.33 7.79 1.88 5.85 13.61 Total 100.08% 99.98% 98.28% 99.77% 99.56% 97.57% 101.00% The first analysis under decomposed syenite represents the first stage in decomposition, while the second analysis represents the last stage in which a kaolin-like residue is produced. The increase in the amount of alumina in all the decomposition products is very noticeable. Residual clays also result from the decomposition of some lime- stones and sandstones. Limestones containing just a small per cent of clay will often form clay beds of appreciable thickness through long continued decomposition. Calcium carbonate is dissolved out by meteoric water containing acids and the insoluble clay accumu- lates. The cementing material of sandstones is dissolved and sand particles and clay particles thus freed are separated by the sorting action of running water. The following analyses of limestone and the residual product exhibit the loss of constituent minerals by decomposition: TABLE 3. LOSS OF CONSTITUENT MINERALS IN THE DECOMPOSITION OF LIMESTONE. Constituent Silicon dioxide (Si0 2 ) Aluminum oxide (A1 2 0 3 ) Iron oxide (Fe 2 0 3 ) Calcium oxide (CaO) Magnesium oxide (MgO) . Sulphur trioxide (S0 3 ) . . . Moisture (H 2 0) Volatile matter (C0 2 etc.) Total Limestone 1 Decom- Fresh posed Fresh 32.81 63.63 20.60 11.15 10.34 7.63 4.65 8.75 4.62 22.69 3.75 41.81 1.53 .50 .81 1.55 .34 .25 2.75 4.25 .85 22.61 7.77 23.15 99.74% 99.33% 99.72% 2 Limestone 3 Decom- Decom- posed Fresh posed 65.30 17.03 76.60 12.63 21.00 18.37 12.18 3.33 2.00 1.50 29.29 .90 .63 .25 .72 .70 4.75 .75 .55 2.27 28.20 .97 99.51% 100.32% 100.09% These samples were taken from the Selma chalk and the residual clay overlying it. ORIGIN AND CLASSIFICATION OF CLAY. 35 Transported Clay . — The residue formed by the decomposition of rocks may not be allowed to remain on the surface where it was formed. By the action of gravity, of water, of wind, or of ice it may be transported and deposited at some distant point. The particles of such residium accumulating upon a slope will, influenced by gravity, gradually creep to the bottom of the slope. The water which falls upon the slope and runs away to the lower levels to form the rills, brooks and larger streams becomes filled with the finer particles, the size of the particles carried being dependent on the velocity of the water, which in turn is dependent upon the slope. A stream having a velocity of only one-third of a mile an hour is sufficient for the transportation of clay particles. Because of the minute size of the particles and their light weight, clay is one of the first materials to be taken away from a residual deposit by running water. When- ever the stream carrying the particles retards its velocity, it drops its load in proportion to the loss of velocity. A small decrease in velocity will cause the loss of only the coarser particles. A sudden and complete loss of velocity would mean the deposition of all sizes of the materials held in suspension. The presence of coarse sand in clays may thus be explained. Rivers may carry fine particles of rock material to lake or sea and as the waters of the stream mingle with the waters of the larger body they lose their velocity and deposit their load. Thus it is that estuary and delta deposits are formed. Carried by ocean currents and redeposited on the sub-aqueous coastal shelf, beds of marine sands and clays are formed, the coarser material being deposited nearest the shore. Deposits of sand, silt and clay are made on the flood-plains of rivers during the overflow periods. The coarser material is thrown down near the banks of the stream, where the water on leaving the channel loses the greater part of its velocity and therefore its capacity for carrying suspended matter. The finer material is carried farther from the channel and, by the sorting action of water, beds of almost pure clay, the finest material, may be found upon the flood-plain. Lacustrine clays are clay deposits formed along the shores and on the bottom of lakes, the material of which is derived from the land and carried in by streams. In a similar way marine clays are formed on the ocean bed. When these clay beds, in the course of deposition, 36 CLAYS OF MISSISSIPPI. become deeply buried under other deposits they become compacted into a firm clay rock called shale. During the glacial period vast quantities of rock material were transported by ice and deposited in an irregular sheet of mantle rock to which the name “drift” has been applied. The drift contains in many places beds of clay called till. Streams of water coming from the front of the melting glaciers carried away the fine particles of clay and rock flour and spread them in some places over large areas. This fine, silty material is called loess. Part of the loess was trans- ported and redeposited by winds, thus producing our second form of loess deposits under the head of eolian deposits. Adobe clays of the plains are thought to be of eolian origin. Classification of Clays. Clays may be classified according to their origin, according to their mode of occurrence; according to their chemical or physical properties, and according to their uses. A large number of classifi- cations have been suggested by different writers on ceramics. None of these classifications are wholly free from objections for the reason that it is difficult to arrange a grouping which will be free from over- laps. The following classification was arranged by Wheeler:* Kaolin. 1. White ware China clay. Ball clay. Plastic fire clay 2. Refractory < Flint clay. Refractory shale. 3. Potter’s Plastic clay and shale of moderate fusibility. Paving brick clay and shale. 4. Vitrifying Sewer pipe clay and shale. Roofing tile clay and shale. Common brick clay and shale. 5. Brick Terra cotta clay and shale. Drain tile clay and shale. 6. Gumbo Burnt clay ballast. 7. Slip Clays of very easy fusibility. ♦Clays of Missouri, p. 25. ORIGIN AND CLASSIFICATION OF CLAYS. 37 Wheeler’s classification is based primarily on the use of clay. As the term implies the first group of clays is employed in the manu- facture of white burning ware. The refractory clays are the fire clays used in the manufacture of fire brick, gas retorts, crucibles, saggars, muffles, etc. Pottery clays are employed in the manufacture of stoneware. Vitrifying clays are used in the manufacture of pav- ing brick, sewer pipe, and roofing tile. Brick clays are those em- ployed in the manufacture of brick, terra cotta and drain tile. Gumbo clays are alluvial clays employed in the manufacture of burnt ballast for road metal. Slip clays are clays of low fusibility and are used to glaze clay wares such as stoneware. In his Economic Geology of the United States Reis gives the fol- lowing form of classification based partly on mode of origin and partly on physical characters: 1. Residual clays. A. White burning (kaolin, formed from feldspathic rocks). B. Colored burning (formed from igneous, metamorphic, and many sedimentary rocks). 2. Clastic, or mechanically formed clays. A. Water formed (of variable extent, depending on locality and mode of deposit). a. White burning (ball and paper clays). b. Colored burning (brick and pottery clays). B. Glacial clays (often stony, all colored burning). C. Wind -formed clays (some loess). 3. Chemical precipitates (some flint clays). The following classification of Buckley (Clays and Clay Indus- tries of Wisconsin) is based on the origin of the deposits: I. Residual, derived from: A. Granitic or gneissoid rocks. B. Basic igneous rocks. C. Limestone or dolomite. D. Slate or shale. E. Sandstone. II. Transported by: A. Gravity assisted by water. Deposits near the heads and along the slopes of ravines. 38 CLAYS OF MISSISSIPPI. B. Ice. Deposits resulting mainly from the melting of ice of the glacial epoch. C. Water. 1. Marine. 2. Lacustrine. 3. Stream. D. Wind. Loess. The classification offered by Ladd (Clays of Georgia) is based on the origin and occurrence of clays. It is given below: Indigenous. A . Kaolins. a. Superficial sheets. b. Pockets. c. Veins. Foreign or transported. A . Sedimentary. a. Marine. 1. Pelagic. 2. Littoral. b. Lacustrine. c. Stream. B. Meta-sedimentary. C. Residual. D. Unassorted. The indigenous clays are those formed in situ and rest upon the rock from which they were derived. The foreign group includes those which have been transported and redeposited. The marine clays were deposited in sea water, the littoral near the shore, and the pelagic in deep water. The lacustrine clays were deposited in lake basins. Stream clays are deposited on the flood plains and in the deltas of rivers. Meta-sedimentary clays are residual clays derived from once transported sediments such as the lighter pyroclastic rocks. Residual clays are those formed by the decomposition of argillaceous sedimentary rocks, such as limestones and sandstones. Unassorted clays include impufie glacial clays which contain sand, gravel and bowlders and are often called bowlder clays. Beyer and Williams use the following classification of which they say: “In the following scheme, which in the main, is the classification offered by Prof. Edward Orton of Columbus, Ohio, the subdivisions ORIGIN AND CLASSIFICATION OF CLAYS. 39 are somewhat more extensive, and while ultimate basis is that of origin, the physical and chemical properties are taken into account in making some of the lesser subdivisions.” Primary or residual clays Entirely decomposed feldspathic rock. . .Kaolin or China clay. , f English Cornwall-stone. Part, ally decomposed feldspath.c rock | Porzellan Erde of the Germans . Highly refractory Flint fire clay. Plastic fire clay. Secondary or transport- ed clays Deposited in < still water Fire clay. . . [ No. 2 fire clay. Moderately refractory . 3 ) 81 .61 .31 9.39 Calcium oxide (CaO) 19 .37 .94 .34 Magnesium oxide (MgO) . . . 13 .13 .35 .70* Sulphur trioxide (SO 3 ) .... 45 .18 .39 .51 Total 100.12 100.57 99.93 98.21 Stoneware Clays. Per Cent Constituent No. 1 No. 2 No. 3 No. A Moisture (H 2 O) 54 .77 .94 1.51 Volatile matter (CO 2 ) 7.40 6.77 6.64 8.07 Silicon dioxide (Si 02 ) 59.12 62.58 67.70 61.69 Aluminum oxide (AI 2 O 3 ) ■ . 27.44 27.58 19.69 24.91 Iron oxide (Fe20j) 4.39 1.57 3.04 2.04 Calcium oxide (CaO) 34 .40 1.06 .34 Magnesium oxide (MgO) . . . 28 Trace .58 .83 Sulphur trioxide (SO 3 ) Trace .19 .20 Total 99.51 99.67 100.84 99.59 Brick Clays. Per Cent Constituent No. 1 No. 2 No. 3 No. A Moisture (H 2 O) 5.50 4.25 1.08 1.80 Volatile matter (C02etc.) . . 5.00 7.77 2.11 4.37 Silicon dioxide (Si02) 67.60 63.63 80.76 75.21 Aluminum oxide (AI 2 O 3 ) . . . 12.55 10.34 8.50 5.47 Iron oxide (Fe 203 ) 7.60 8.75 4.50 5.47 Calcium oxide (CaO) 80 3.75 1.50 .87 Sulphur trioxide (SO 3 ) 17 .34 .04 .52 Total 100.00 99.33 98.94 98.88 Reis has summarized the facts to be obtained from the ultimate analysis of a clay as follows (see N. J. Geol. Survey, Vol. VI): ♦Includes potassa and soda. CHEMICAL PROPERTIES OF CLAY. 45 “1. The purity of the clay, showing the proportion of silica, alumina, combined water and fluxing impurities. High grade clays show a percentage of silica, alumina and water, approaching quite closely to those of kaolinite. “2. The refractoriness of the clay, for, other things being equal, the greater the total sum of fluxing impurities, the more fusible the clay. “ 3 . The color to which the clay burns. This may be judged approximately, for clays with several per cent or more of ferric oxide will burn red, provided the iron is evenly and finely distributed in the clay, and there is no excess of lime. The above conditions will be affected by a reducing atmosphere in burning, or the presence of sulphur in the fire gases. “ 4 . The quantity of water. Clays with a large amount of chem- ically combined water sometimes exhibit a tendency to crack in burning, and may also show high shrinkage. If kaolinite is the only mineral present containing chemically combined water, the percentage of the latter will be approximately one-third that of the percentage of alumina, but if the clay contains much limonite or hydrous silica, the percentage of chemically combined water may be much higher. “ 5 . Excess of silica. A large excess of silica indicates a sandy clay. If present in the analysis of a fire clay it indicates low refrac- toriness. “6. The quantity of organic matter. If this is determined sepa- rately, and it is present to the extent of several per cent, it would require slow burning if the clay was dense. “7 . The presence of several per cent of both lime (CaO) and car- bon dioxide (C0 2 ) in the clay indicates that it is quite calcareous.” In order to determine the amount of clay substance in any of the analyses given in table 5, we may consider all the clay minerals to have the same chemical composition as kaolinite (A1 2 0 3 , 2Si0 2 + 2H 2 0) . The average composition of some beds of kaolin is very close to the theoretical composition of kaolinite. The latter contains 39.5 per cent of alumina, 46.5 per cent of silica and 14 per cent of water. However, some beds of pure kaolin may exhibit less alumina than is contained in kaolinite. Such would be the case were the predomi- nant mineral cimolite. On the other hand the amount of alumina 46 CLAYS OF MISSISSIPPI. present might exceed the amount in kaolinite. In this case the pre- dominant mineral might be collyrite or a mixture of some other of the aluminum silicates with gibbsite. The amount of alumina in the first kaolin in the table above given falls a little below the amount in kaolinite. To obtain the percentage of kaolinite from the ultimate analysis multiply the quantity of alumina (38.82) by the factor 2.53 and the result obtained, is 98.21 per cent instead of 100 per cent, as it would have been in the case of pure kaolinite. Now, if the amount of alumina be multiplied by the factor, 1,176, the amount of silica which enters into combination with the alumina to form kaolinite may be obtained. The amount of combined silica is found to be 45.65 per cent. But the total amount of silica is only 44.23, so that there is lacking 1.42 per cent of the silica necessary to combine with the alumina to form kaolinite. Two explanations are relevant. The kaolin may be composed largely of a mineral like collyrite, which is higher in percentage of alumina than kaolinite. Under such con- ditions there would be some free silica in the kaolin. The same con- ditions might be brought about as the result of a mixture of these two minerals, collyrite and kaolinite. On the other hand, this compo- sition of the kaolin may be explained by assuming the presence of aluminum oxide (gibbsite) with the aluminum silicate or silicates. Kaolin No. 2 of table 5 contains 1.8 per cent more alumina than is required for kaolinite. It also contains 7.64 per cent less silica than the amount required to satisfy the alumina. Computed as kaolinite it contains 104.48 per cent. This condition very strongly suggests the presence of gibbsite. The amount of kaolin in the first stoneware clay of table 5 is 69.42 per cent and the amount of silica is 26.86 per cent. The de- crease in the amount of clay substance in the brick clays is still more marked. The first in the table contains the highest per cent, 31.75. More than half of this clay consists of uncombined silica. CHEMICAL COMPOUNDS OF ULTIMATE ANALYSIS. Before taking up a discussion of the minerals commonly occurring in clays a short discussion of the chemical compounds revealed by the ultimate analysis will be given. CHEMICAL PROPERTIES OF CLAY. 47 SILICA. The silica, the percentages of which are expressed in the analyses of table 5, may be divided, in respect to its influence on the clay, into three parts. The first portion is that which is combined with the alumina to form the kaolin group of minerals. The second por- tion is combined with other silicates, such as feldspar, hornblende and mica. The third portion is uncombined silica known as free silica or sand. In making a rational analysis of a clay the last two are rarely separated. The usual method is to compute the amount of silica combined to form kaolinite. This amount called combined silica is deducted from the total amount of silica as revealed by the ultimate analysis and the remainder is called free silica. Reis has pointed out that this method is not entirely satisfactory from the clay workers’ standpoint, since some of the silicates have very differ- ent properties from the quartz and may exert a very different influ- ence on the clay ware. The effects produced upon clay by the pres- ence of free silica are to influence its texture, its bonding power, its plasticity, its strength, its fusibility and other physical properties. These effects are discussed under physical properties of clay. » ALUMINA. The alumina revealed by the chemical analysis is derived largely from the kaolin in the clay, but a part may be derived from feldspar and other aluminous minerals. The amount of alumina in the Mis- sissippi clays thus far analyzed ranges from a few per cent to 41 per cent. Alumina is the most refractory substance found in clays. Besides contributing to the refractoriness of the clay it also furnishes the bonding material for holding together the inert particles. With- out its presence the material could not be fashioned into the desired form. Part of the water found in clay is in chemical union with alumina to form some hydrous silicate like kaolinite. Besides the kaolinite there are other minerals which contain water of crystallization, such, for example, as gypsum. The combined water is given up when the clay is subjected to high temperatures. Clay also contains some mechanically combined water which may be driven off at the tem- perature of boiling water. The amount of mechanically combined water is given in the ultimate analysis under the head of moisture. 48 CLAYS OF MISSISSIPPI. IRON OXIDE. The amount of iron oxide varies in different clays. It is generally least in kaolins and highest in brick clays. The chief source of iron oxide in clay is from compounds of iron, but a small amount may be derived from ferro-magnesian minerals. The iron compounds, such as hematite, limonite and siderite, may exist either in a finely divided state or as concretions in the clay. Limonite on the application of heat loses its water of crystallization and becomes red oxide of iron. It is to this last compound that the red color of clay wares is due. Siderite, the carbonate of iron, under the influence of heat gives up its carbon dioxide and becomes ferrous oxide. In the presence of oxygen the ferrous iron may be changed to the ferric oxide, the red oxide. The sulphide of iron may also be reduced to the ferric oxide under the action of heat. Iron is also a fluxing ingredient of clays. When the iron compound is reduced to the ferrous state in the absence of oxygen it will unite with silica forming a ferrous silicate. In the presence of other easily reducible compounds the ferrous silicate may act as a rapid solvent. If there is plenty of oxygen present the ferrous oxide will be further oxidized to the more refractory ferric state. CALCIUM OXIDE (LIME). The amount of lime in clays is generally below five per cent. Some brick clays, however, contain as much as twenty per cent. The origin of the lime is from limestone (calcium carbonate) and gypsum (calcium sulphate). Small amounts of lime may be derived from lime-bearing silicates, some of which are of common occurrence in clays. The effect produced by the presence of lime in clay will depend on the distribution of the lime and the amount present. Lime concretions may produce cracks in bricks by absorbing water and slaking after the brick are burned. In the presence of iron these concretions may fuse and cause cavities or slaggy masses in the brick. The same amount of lime finely divided and uniformly distributed through the clay would have no detrimental effect. However, since lime acts as a flux, its presence in appreciable quantities tends to lower the fusion point of the clay. For this reason vitrifying clays should not contain much lime. In the presence of a considerable CHEMICAL PROPERTIES OF CLAYS. 49 quantity of iron the fluxing action of lime may be rapid and effective . With only a small increase of temperature above incipient fusion the brick may be reduced to a slaggy mass. Lime in considerable quan- tities in a common brick clay may also prevent the development of a red color in the ware. MAGNESIA. The source of magnesia in clay is from magnesium carbonate, from magnesium sulphate, and more rarely from silicates containing magnesium. Dolomite or magnesium limestone is the chief source. This mineral is a calcium-magnesium carbonate (J Ca, i Mg, C0 3 ). By the decomposition of pyrite in clays sulphuric acid may be formed. The latter may attack the magnesium carbonate and form magnesium sulphate. The sulphate is soluble in water and if the drainage of the clay bed is perfect it will cause the sulphate to be carried out by circulating waters. If the sulphate is not separated from the clay it will be brought to the surface of the ware either in drying or burn- ing and produce efflorescence. The action of magnesia under heat is said to correspond to that of lime with the exception that at high temperatures the magnesia is not as rapid a fluxing agent as lime. ALKALIES. The alkalies commonly found in clays are potash (K 2 0) and soda (Na^jO). The per cent of alkalies contained in the clays of Mis- sissippi so far determined is small. Alkalies in clays are commonly derived from silicate mineral, such as feldspar. The compounds of potassium and sodium formed by the breaking down of these com- plex compounds are sulphates, carbonates and chlorides. These compounds being soluble are removed from the clay under perfect drainage conditions. Imperfectly drained clay beds may contain a considerable amount of these compounds. The alkalies act as powerful fluxes. They fuse at a low temperature, the soluble salts at about red heat. The silicates fuse at higher temperatures. The soda silicates fuse at lower temperatures than the potash silicates The feldspars are considered an aid to vitrification since they produce a longer period, between incipient fusion and complete vitrification They are detrimental to high degree of refractoriness 50 CLAYS OF MISSISSIPPI. MINERALS IN CLAYS. The minerals composing clays may be classed as essential and non-essential. The determination of essential components will be controlled by the use for which the clay is intended. Iron, for ex- ample, is an essential element in any clay intended to be red -burning. On the other hand it is non-essential and detrimental to a clay in- tended to be white-burning. The minerals most commonly found in clays are silica, feldspar, mica, iron compounds, such as hematite, limonite, magnetite, siderite and pyrite, kaolinite, calcite, gypsum and hornblende. Others occurring somewhat less commonly are rutile, glauconite, dolomite, garnet and fluorite. Pure clay is a mixture of kaolinite, meershalumi- nite, halloysite, newtonite, cimolite, pyrophyllite, allophane, colly rite, montmorillonite and schrotterite, silicates of aluminium and gibbsite, an oxide of aluminium. Rock formed of one or more of these minerals is called kaolin. All the other minerals found in clay are termed impurities. The clay compounds and the impurities result from the decay of rocks. For example, granite composed, say, of feld- spar, mica and quartz, may, by decomposition, form allophane, cimolite, kaolinite, biotite, quartz, magnetite, damourite, epidote, gibbsite, muscovite, chlorite, diaspore, limonite, pyrophyllite, new- tonite, hematite and hypersthene. Further alteration may result in the formation of other compounds. In the following pages a dis- cussion of the properties of some of the minerals commonly found in clays are given. KAOLINITE. Kaolinite (A1 2 0 3 , 2Si0 2 , 2H 2 0) is an hydrous silicate of aluminum containing 46.5 parts of silicate; 39.5 parts of alumina and 14 parts of water. It is a compact friable or mealy mineral having a greasy feel. It is composed of microscopic scales or crystals which in the aggregate are white in color. It is a soft mineral having a specific gravity of 2.63. Kaolinite results from the decomposition of alumi- nous minerals, especially the feldspars, one of the common and essen- tial constituents of granites and gneisses. It is found in the rocks of all ages from the Archean to the Recent. Some of the varieties of kaolinite contain more alumina and less water than that in the for- CHEMICAL PROPERTIES OF CLAYS. 51 mula given above. Beds of kaolinite and associate minerals are called kaolin. In the decomposition of feldspar to form kaolin, the potash and other bases are removed by the action of meteoric waters containing carbon dioxide. The residual aluminium silicate takes up water, forming an hydrous aluminium silicate or oxide. The aluminous minerals found in kaolin are here given : TABLE 6. ALUMINOUS MINERALS FOUND IN KAOLIN. Silica Alumina Water Kaolinite, H 4 AI 2 (S^Og) 46.05 39.5 14.0 Meerschaluminite, 2HA1 (SiOO + aq 43.15 41.07 15.78 Halloysite, ^A^S^Og) + aq 43.5 36.9 19.6 Newtonite, H 8 Al2(Si20n) + aq 38.5 32.7 28.8 Cimolite, H 6 Al<(Si 03 )g + aq 63.4 23.9 12.7 Pyrophyllite, H2Al2(SiOs)4 66.7 28.3 5.0 Allophane, Al2(Si0 8 )5H20 23.8 40.5 35.7 Colly rite, Al 4 (Si0 8 )9H 2 0 14.1 47.8 38.0 Schrotterite, Al4(SiO 8 )30H2O 11.7 53.1 35.2 Gibbsite, AI 2 O 33 H 2 O 65.4 34.6 SILICA. Silica (Si0 2 ) is usually the most abundant mineral in clays. The composition of silica is silicon, 46.7 parts and oxygen, 53.3 parts. It exists in clay either free or combined. Combined with other substances it forms silicates. The amount of free silica or quartz sand occurring in clay varies from 1 to 50 per cent. The total amount of silica may be much higher, often as much as 70 or 80 per cent. In such clays the percentage of free silica is very high. The size of the quartz grains in clays is extremely variable. They range from those particles large enough to be removed by screening to those of exceedingly small microscopic size. The grains are trans- parent, of milky translucence or stained by iron compounds. Quartz grains which have not been transported are usually angular in form. The transported grains have become rounded by the abrasion incurred during transportation. Since quartz is a very hard mineral, being seventh in the scale of hardness, it is not easily broken up, and because of its insolubility it is not easily decomposed. For these reasons it forms a considerable portion of many sedimentary rocks, and especially of the mantle rock. 52 CLAYS OF MISSISSIPPI. Quartz alone is nearly infusible, being fused at cone 35 of the Seger series, a temperature of about 3,326° F. Although of such high refractoriness it may or may not add to the refractoriness of a clay. Under certain conditions, as when the amount of fluxing materials is high, an addition of quartz may raise the fusion point, but such fusion point will be much lower than the fusion point of pure quartz. Quartz added to clay having a low per cent of fluxing impurities may tend to lower the fusion point of the clay. The addition of quartz to clay will reduce the shrinkage of the clay. It will also decrease the plasticity but the amount of reduc- tion will depend on the size of the quartz grains. Clays containing a high percentage of quartz of coarse grain slake more readily than other clays. Clays containing a high percentage of very finely divided quartz slake slowly and are very sticky clays. Quartz of coarse grain adds to the porosity and absorption power of a clay. IRON. The element iron may occur in clays in a number of forms. It may be present as a sulphide, an oxide, a carbonate, an hydroxide, a sulphate or a silicate. In the manufacture of some clay wares a limited amount of iron is desirable. For instance in red ware such as brick and tiling the color is dependent on the oxidation of the iron compounds in the clay. A very low per cent of iron is desirable in a clay to be used in the manufacture of white ware of any kind. Some clays burn white notwithstanding the presence of a large per cent of iron; especially is this true when a considerable portion of carbonate of lime is present. The iron compounds commonly found in clays are limonite, hematite, siderite and pyrite. Limonite . — Limonite is an hydroxide of iron (2Fe 2 0 3 , 3H 2 0). It contains 59.8 per cent of iron, 25.7 per cent of oxygen, and 14.5 per cent of water. As an ore it may occur in rather compact crys- talline masses or as grains mixed with clay, in which form it is called yellow ochre. The yellow or brown color of many clays is caused by the presence of appreciable amounts of limonite. Limonite may occur in clays as a coating for the sand grains, as distributed through the clay in very fine particles, and as large lenticular concretions. It occurs as bog ore in ponds and marshes, having been brought into the water in a soluble form as a sulphate or carbonate or as some CHEMICAL PROPERTIES OF CLAYS. 53 organic salt through the action of some organic adid. It is precipi- tated by oxidation and its presence is revealed by an iridescent oil-like film upon the surface of the water. Limonite may result from the alteration of other ores, through the action of atmospheric agents and the presence of organic acids. Through alteration pro- cesses it is derived largely from pyrite, magnetite, siderite and from silicates containing iron in the ferrous state. Under the action of carbon dioxide it may be changed to siderite. By hydration it may be changed to hematite. It forms the cementing substance for many sandstones and conglomerates. Under the influence of heat limonite loses its water of crystallization and is changed to the red oxide. Hematite . — The red oxide of iron (Fe 2 0 3 ) is also a common con- stituent of clays. This compound contains 70 per cent of iron, and 35 per cent of oxygen. It is found widely distributed through the rocks of the earth’s crust. It occurs in the form of tabular or rhom- bohedral crystals known as specular iron. In hexagonal plates it is known as micaceous hematite. In minute particles it is found as a coating for sand grains and is also disseminated through clays and other rocks of this form. It sometimes occurs in clays in concre- tionary masses. These masses may be coated with limonite which is the beginning of the process of alteration. In beds of soft rock it forms red ochre. The occurrence of hematite may be due to the alteration of some other iron compound. For instance pyrite by oxidation may be changed to hematite. Magnetite and siderite may also be altered to hematite. Silicates such as hornblende, for example, may be decomposed, producing hematite as one product. Hematite may be altered to magnetite and then changed to siderite by the action of carbon dioxide. When acted on by sulphuretted hydrogen it may form pyrite, or by taking up water it may become limonite. Siderite . — The carbonate of iron (FeC0 3 ) may occur in clays as minute particles somewhat uniformly distributed and as concre- tionary masses. Siderite contains 62.1 per cent of iron protoxide and 37 . 9 per cent of carbon dioxide. It is found in many sedimentary and metamorphic rocks. In shales and clays it frequently occurs as iron stones, especially in beds associated with coal deposits. There are several varieties based on composition. Some of these contain magnesium, others manganese, and still others calcium. There are 54 CLAYS OF MISSISSIPPI. also several varieties as to form. It may be crystalline, earthy, concretionary, granular, compact or oolitic. Where uniformly distributed through clay it may give it a slate color. By oxidation siderite may be altered to hematite, to limonite or to magnetite. When present in considerable quantities in a clay it may act as a flux, causing the clay to be fused at a lower tempera- ture. When heated it loses its carbon dioxide and becomes ferrous iron (FeO). The FeO may unite with silica and form a ferrous silicate, Fe0 2 , 2Si0 2 , which gives to the ware a dark green color. Pyrite . — Iron pyrites or fool’s gold is a bright brassy mineral of common occurrence in clays and shales. Its chemical symbol is FeS 2 , and its composition is iron 46.6 per cent and sulphur 53.4 per cent. Its common occurrence in clay is in the form of crystals or concretionary nodules of various shapes. Many of these are radiate in structure. In the presence of air and moisture the pyrite (FeS 2 ) alters to iron sulphate, iron oxide and sulphur. If lime carbonate is present the iron may be changed to the hydroxide and the sulphur trioxide uniting with the calcium may form gypsum (CaS0 4 , 7H 2 0). Thus by the action of weathering pyrite may be removed from clay. Pyrite may be changed to limonite by oxidation and hydration. By dehydration the limonite may be altered to hematite. When FeS 2 is subjected to heat the Fe becomes oxidized to FeO and the sulphur is converted into S0 2 or S0 3 . At low temperatures FeS 2 loses S and becomes FeS. At still higher temperatures FeS is changed to FeO and S0 2 . In the presence of oxygen the S0 2 may be converted into S0 3 . Marcasite . — Marcasite is a variety of iron disulphide having the same chemical composition as pyrite. It is a common impurity in lignitic clays. Its color is pale bronze-yellow. In clays it frequently occurs in nodules of radiating crystals called “sulphur balls.” Atmos- pheric alteration of marcasite takes place very rapidly. For this reason weathering the clay is one of the most effective means of removing the impurity. Ilmenite . — The mineral ilmenite, or menaccanite, is an oxide of iron and titanium (TiFe0 3 or (TiFe) 2 0 3 ). It is an opaque mineral of black or brownish-black color. The normal variety contains 31.6 per cent of titanium, 36.8 per cent of iron, and 31.6 per cent of CHEMICAL PROPERTIES OF CLAYS. 55 oxygen. Since this mineral is very refractory and not easily acted on by the agents of decomposition, it is a common constituent of many residual and transported deposits. It also occurs as an original constituent of many igneous rocks. It is sometimes found in tabular crystals, plate like masses or in grains in veins of metamorphic rocks. In many sedimentary rocks it is present in small rounded grains. There are a number of varieties of the mineral distinguished by varying proportions of iron and titanium. In some species the iron is partly replaced by magnesium. Ilmenite may be altered to leu- coxene or titanite. GYPSUM. Gypsum (CaS0 4 2H 2 0) is a hydrous sulphate of calcium. It is composed of 32.6 parts of lime, and 20.9 parts of water, and 46.5 parts of sulphur trioxide. Gypsum occurs as individual crystals, as crystalline aggregates, as crystalline sands, or in massive beds of earthy material. It may be precipitated from sea water under con- ditions similar to the deposition of common salt. It may also result from the decomposition of pyrite in the presence of lime carbonate. The reactions involved are as follows: FeS 2 + 60 = FeS0 4 + S0 2 or FeS 2 + 30 + H 2 0 = FeS0 4 + H 2 S. Then FeS0 4 + 20 + 7H 2 0 = 2Fe 2 0 3 :3H 2 0 + 4H 2 S0 4 . In the presence of lime CaC0 3 + FeS0 4 = CaS0 4 + 2H 2 0 + FeC0 3 or H 2 S0 4 -f- CaC0 3 = CaS0 4 T H 2 O -l- C0 2 . There are several varieties of gypsum, the clear, transparent, crystalline kind is called selenite. Satin spar is a fibrous variety with a satin-like lustre. Alabaster is a white, fine-grained variety used in making ornaments. Gypsite is an earthy variety occurring in thick beds of varying purity. Selenite and gypsite both occur in some of the clays of Mississippi. Aggregates of selenite crystals are of common occurrence in the clays of the Jackson group. By the decomposition of pyrite in the Selma chalk the residual clays of that formation contain sufficient gypsum in some localities to cause efflorescence on brick manufactured from the clay. A discussion of the effects of gypsum may be found under lime and efflorescen e. 56 CLAYS OP MISSISSIPPI. CALCITE. The mineral calcite (CaC0 3 ) is composed of 56 parts of lime (CaO) and 44 parts of carbon dioxide (C0 2 ). Calcite is the chief constituent of limestone, chalk and marble. It occurs also in marls, shales and sandstones in small grains or crystals. Its presence in sedimentary rocks is largely due to the accumulation of organic remains, and possibly to a less extent to precipitation from aqueous solutions. There are several varieties of calcite. Iceland spar is a clear transparent variety having the power of double refraction. Dog-tooth spar occurs in crystals, the form of which suggests the name. Aragonite has the same chemical composition as calcite but differs in its crystallization. Marble, or crystalline limestone, is composed largely of calcite. Tufa, travertine and argentite are composed principally of calcium carbonate. When calcite is heated to a temperature of 1,296° F the C0 2 in composition is driven off and lime (CaO) remains. On the addition of water the calcium oxide (CaO) will be changed to calcium hydroxide (Ca (OH) 2 ) with the evolution of heat. Nearly all clays contain at least small quantities of calcite. The presence of calcite tends to lower the fusion point of the clay. Where present in large quantities or where unevenly distributed it may produce cracking or breaking of the brick due to the evolution of gas and of heat in slaking. Unless the brick are porous it is possible for the outside of the brick to vitrify before all of the gas has been expelled from the inside. This causes a swelling or puffing of the brick. Many residual clay deposits have been formed by the decom- position of limestone containing clay. The lime carbonate is dis- solved by acidulated meteoric waters and carried away, while the insoluble clay is left as a residual product. The amount of clay in the limestone may be exceedingly small, yet in time and under the proper conditions a bed of clay of considerable thickness may accumulate. Such residual clays have been formed in Mississippi by the dissolution of the Selma chalk and the Vicksburg limestone. Beds of clay so formed usually rest directly upon the surface of the limestone and often contain, especially in the lower portions, nodules of lime carbonate which represent the more insoluble parts of the limestone. These are often a source of annoyance to the brick maker. They interfere with the cutter and cause flaws in burning CHEMICAL PROPERTIES OF CLAYS. 57 If the bottom clay is used it ought to be crushed so as to distribute the lime through the clay, in which condition it is harmless. FELDSPAR, The feldspars are silicates of aluminum containing calcium potas- sium, sodium or barium. There are nine principal varieties which are divided crystallographically into two groups: first, the mono- clinic feldspars, orthoclase and hyalophane; second, the triclinic feldspars, microcline, anorthoclase, albite, oligioclase, andesine, labradorite and anorthite. The chemical constituents of each of these feldspars is given in the following table from Dana’s Mineralogy : TABLE 7, CHEMICAL COMPOSITION OF FELDSPARS (DANA). Silica Alumina Potash Soda Lime Barium Species Si 02 AI 2 O 3 K 2 O Na 20 CaO Ba Orthoclase 64.7 18.4 16.9 .... .... .... Hyalophane 52.0 22.0 7.0 3.0 1.0 15.0 Microcline 65.0 18.0 17.0 .... .... .... Anorthoclase 66.0 20.0 4.0 7.0 1.0 .... Albite 68.0 20.0 12.0 12.0 Oligioclase 62.0 24.0 . . . . 9.0 5.0 .... Andesine 57.0 27.0 9.0 7.0 Labradorite 53.0 30.0 .. . 4.0 13.0 .... Anorthite 43.0 37.0 ... .... 20.0 .... Feldspar is found in crystals in igneous and metamorphic rocks and as grains in some fragmental rocks. It is one of the essential constituents of granite. By the action of carbonate waters on lime and other bases of feldspar they may be taken into solution and the feldspars decomposed. The decomposition of the feldspar results in the formation of new compounds. These new compounds are aluminous silicates like kaolinite. The decomposition of pyrite may produce sulphuric acid which will aid in the decomposition of feldspar. The decomposition of feldspathic rocks is the original source of clay. Feldspar is commonly associated with quartz in sand and is for that reason a constituent of most clays. Like quartz it serves to decrease shrinkage in clays, but since it fuses at a much lower temperature (2,192° F) it may form a chemical union with other substances and act as a flux. 58 CLAYS OF MISSISSIPPI. MICA. Mica is a polysilicate composed of iron, aluminum, calcium, magnesium, manganese and silica. The mica group of minerals con- tains more than a half dozen important varieties. They are all silicates of aluminum but vary in other constituents, viz. : potas- sium, lithium, magnesium and iron. There are two common varieties. The first is a white variety called muscovite. It has the following composition: silica, 45.2 per cent; alumina, 38.5 per cent; potash, 11.8 per cent, and water, 4.5 per cent. The second is a black or dark variety, called biotite (Mg, Fe) 2 Al 2 Si 3 0 12 ), the potassium of the former being partly replaced by magnesium and iron. One of the most notable physical characters of mica is its perfect cleavage in one direction permitting it to be separated into very thin plates. It has a low degree of hardness. Mica is an essential constituent of many igneous and metamorphic rocks. When granite and other mica-bearing rocks are decomposed the crystals of mica are broken up into small thin flakes. These flakes are found in residual clays, and on account of the low specific gravity of the particles, are transported long distances and occur in most transported deposits. Under the action of weathering mica may lose its potash and take up water and soda, manganese or lime. In brick clays the mica grains may be little affected by a temperature sufficiently high to produce a serviceable brick, and the bright unchanged par- ticles are sometimes seen upon the surface of a fresh fracture. At high temperatures the mica may be fused and it is therefore detri- mental to fire clays if present in sufficient amount. Because of the presence of iron it is detrimental to white ware burned at high tem- peratures. HORNBLENDE. Hornblende is a silicate belonging to the amphibole group of bisilicates. In contains 48.8 parts of silica; 18.8 parts of iron; 13.6 parts of magnesia; 10.2 parts of lime and 1.1 part of man- ganese. It may occur in crystals, fibers or in a massive form. It is an essential constituent of diorite, and also occurs in other rocks. There are many varieties of hornblende. Actinolite, asbestus, CHEMICAL PROPERTIES OF CLAYS. 59 nephrite and tremolite are light colored varieties. Pargasite, bera- maskite and black hornblende are varieties of the dark colored am- phiboles. There is a great variety of colors. The predominant colors are black, white, green and brown. Hornblende is hard and has a vitreous or silky lustre. The residual product of the decom- position of hornblende is a clay which contains a high per cent of iron. The iron compounds which may be formed by its decomposi- tion are limonite, magnetite and hematite. CHAPTER III. PHYSICAL PROPERTIES OF CLAY. The physical properties of clay which, from the clay-workers’ standpoint, are most valuable, are plasticity, strength and refractori- ness. Plasticity enables the worker to fashion the clay into the desired form. The strength of the clay permits the clay ware to be handled during the drying and burning processes without danger of breakage. The power of the clay to withstand high temperatures permits it to be burned to a compact, hard body of permanent form. While these are, for the majority of wares, the most important physical properties there are other properties of very great importance in the manufacture of some wares. In our investigation of the clays in- cluded in this report, we have considered the following properties: Structure. Feel. Shrinkage. Odor. Specific gravity. Taste. Color. Slaking. Hardness. Plasticity. Fusibility. Fineness of grain. Bonding power. Tensile strength. Porosity. STRUCTURE. The structure of a clay refers to its mode of occurrence in the out- crop or pit. A stratified clay is one which occurs in layers. A mas- sive clay is one in which no division planes are seen. A clay which splits readily in thin leaves or irregular blocks is said to be shaly. If the leaves are small, thin and light the term chaffy is applied to it. A slaty clay is one in which the laminae have undergone a consid- erable degree of induration. Instead of occurring in layers some clays are found in concretionary or pebbley masses. Joint clays are those which are separated into blocks by vertical crevices. This structure is an aid to the mining of many clays. These various structures in clay are the result of deposition, compression, and induration. In the process of weathering they are obliterated, and the rapidity of such weathering action is often dependent on the 62 CLAYS OF MISSISSIPPI. structure of the clfcy . The speed with which a mineral producing soluble salts can be removed by weathering will depend upon the structure of the clay. In order that clay may be used in the forma- tion of clay wares, it must be reduced to a structureless mass. For this purpose it is necessary to employ disintegrating or pulverizing machinery. The expense of this process will be determined by the degree of induration which has taken place in the clay structure. SHRINKAGE. The amount which a clay contracts in passing from a plastic con- dition to that of a rigid solid is termed its shrinkage. The water which is added to the clay in order to render it plastic is lost by evap- oration, causing a loss of volume. The loss of volume or shrinkage varies greatly in different clays and with different conditions of the same clay. Water added in excess of the amount required for plas- ticity will cause a greater loss of volume, as will also the presence of air bodies in the clay. Considerable water may exist in the clay without increasing the volume, but whenever the particles of clay are completely enveloped in water, the volume and the plasticity will be increased. Water absorbed by a clay exists either inter- stitial, i. e., in the pores, or interparticle, i. e., not occupying the pores but causing a separation of the particles. It is the latter which increases the volume of a clay. Clays of coarse grain have large interstices and contain large quantities of interstitial water, but less interparticle water than clays of finer grain; therefore, the fine grain clay shrinks more than the coarse grain. j AIR SHRINKAGE. The amount of contraction which a clay undergoes when drying in the air is called its air shrinkage. The amount of air shrinkage depends mainly on two factors; first, the amount of water absorbed; second, the size of the grain. A number of methods of preventing excessive shrinkage is employed. The method more generally in use is that of mixing a sandy clay with the more plastic clay. Under ordinary conditions this is the most economical method. In the greater part of the sur- face clay deposits of this State the upper portion of the clay bed contains available sandy clay. The plastic, residual clays are some- times diluted with the underlying non-plastic loess. Pure sand and crushed brick are sometimes used to decrease shrinkage and produce Plate III. A. BRICKETTES FOR TENSILE STRENGTH TEST. B. ELECTRIC FURNACE FOR TESTING CLAYS. PHYSICAL PROPERTIES OF CLAYS. 63 more rapid drying. Crushed coal cinders are successfully employed in some plants. Chopped straw, sawdust, lignite and coal dust may also be employed. The effects produced by the use of non-plastic materials is to decrease its plasticity and its bonding power. On the other hand, they may cause the clay to mold without lamination, increase the speed of drying and burning, and prevent cracking and checking. The use of combustible substances leaves the brick more porous than the mineral substances. From a fuel standpoint their use is economical, since the clay particles are brought in immediate contact with the clay. The danger of swollen ware will be referred to under the subject of “Causes of Swollen Brick.” Unless a large amount of oxygen is supplied to the kiln in the draft the organic matter in the clay may rob the iron compounds of their oxygen and cause a pale yellow color in red burning clays. The use of cinders is free from some of these objections. They decrease shrinkage, plasticity, bonding power, and tensile strength in the raw clay. They cause the clay to dry more rapidly and to burn in less time. They do not increase the porosity of the clay as do the combustible substances and the tensile strength of the burned clay is not dimin- ished as much. The table below shows the effect of coal and cinder dilution on the tensile strength of raw and burned clays. TABLE 8. EFFECT OF COAL AND CINDER DILUTION ON THE TENSILE STRENGTH OF RAW AND BURNED CLAYS. Locality Starkville brick clay Starkville brick clay and 10% coal . . Starkville brick clay and 10% cinders Amory brick clay Amory brick clay and 10% coal Amory brick clay and 10% cinders. . . Morton clay Morton clay and 10% coal Morton clay and 10% cinders Wahalak clay Wahalak clay and 10% coal Wahalak clay and 10% cinders Tensile strength in pounds per square inch. Raw clay Burned clay 133 146 119 150 75 153 100 220 140 263 176 300 81 131 130 192 100 235 112 170 77 222 74 150 The first clay is residual Selma, the second is Tombigbee second bottom, the third is a residual Jackson and the fourth belongs to the Porter’s Creek (Flatwoods) formation. These clays are all highly 64 CLAYS^OF MISSISSIPPI. plastic and the shrinkage is excessive. The non-plastic material was added to decrease shrinkage and to increase the speed of drying and burning. All of these objects were attained, and, as the experi- ments seem to prove, not greatly at the expense of the strength of the ware when the ware is compared with that of the original clay. The brickettes were given a medium burn. FIRE SHRINKAGE. The loss of volume which the clay sustains in passing from the raw to the burned condition is termed its fire shrinkage. The loss of the chemically combined water in clay and the combination of the organic matter causes an increase in the porosity of the clay. When the temperature is carried to the point of vitrification the pore space and the natural pores are closed. A loss of volume results. Sandy clays not burned to vitrification may not exhibit any fire shrinkage. Some clays containing a high per cent of organic matter when subjected to a rapidly increasing temperature may become viscous on the outside, thus preventing the escape of hydrocarbons formed from the distillation of the organic matter and causing the brick to slightly increase in volume. The following table shows the air shrinkage and the fire shrink- age of some Mississippi brick clays burned at a good red heat and forming a medium burn. TABLE 9. SHRINKAGE IN MISSISSIPPI CLAYS. Formation locality Air Shrinkage Fire Shrinkage Brown loam (middle) 3i% 0 % •i <• 3i% 0 % “ “ (bottom) . .Sardis 6f % 2 % “ “ 3i% 1 % Yazoo alluvium (buckshot) .... 10 % 2 % “ «« *« Moorhead 15 % 3 % 2h% .. , . . Greenville . . . . 10 % “ (candy) 5 % 1 % “ “ 4 % 2f% « “ “ . . Minter City 5 % 1 % 2 % Porter’s Creek (Flatwoods) . . . . 10 % «« ... 10 % 2 % “ “ . .Starkville ... 10 % 1 % Lafayette . . Canton 8 % 0 % “ . .Hernando 5 % 1 % Jackson . .Canton ... 10 % 1 % “ . .Morton ... 10 % 1 % “ . .Barnett ... 10 % 2 % Buhrstone . . Vaiden. ... 10 % 0 % Selma residual . .Starkville 5 % 1 % “ “ . .West Point 4 % 0 % “ “ . .Booneville 5 % 1 % “ “ . .Verona 5 % 1 % PHYSICAL PROPERTIES OF CLAYS. 65 SPECIFIC GRAVITY* The specific gravity of a rock is its weight compared with the weight of an equal volume of distilled water at 60°F. The specific gravity of a substance is obtained by weighing it in air and by weigh- ing it in water and then dividing its weight in air by its loss of weight in water. The specific gravity of clays usually varies from 1.50 % to 2.50, but there are some clays whose specific gravity is lower and others whose specific gravity is higher than these limits. Pure kaolin has a specific gravity of from 2.4 to 2.6. Pure quartz sand has a specific gravity of from 2.5 to 2.8. Where clay is largely a mixture of varying proportions of these two minerals, its specific gravity is not far from 2.5. Clays containing in addition to these minerals mica and limonite are slightly heavier. The presence of magnetite, however, may greatly increase the specific gravity, while on the other hand organic matter may decrease it. Methods of determining specific gravity are not uniform and different methods may produce different results in the same clay. By the use of the pycnometer the specific gravity of the individual grains is determined and taken as the specific gravity of the clay. By another method the specific gravity of lumps of clay whic^i have been coated with paraffin is determined. This method considers the pore space a part of the clay. The specific gravity of any clay is less by the latter method. COLOR. The color of clays is an exceedingly variable property. Many shades and tints are represented. The color may be due either to the presence of organic matter or to the presence of iron and man- ganese compound. Shades of red, buff or brown are generally due to the presence of iron oxides. Blue and dark colors are sometimes caused by the presence of iron carbonate or of organic matter. White clays are devoid of susceptible coloring matter, but some white clays have color developed by burning. By the color of the raw clay it is not possible to predict the color of the burned product unless the nature of the coloring matter and its amount are known. Some white clays contain enough iron to produce a dark shade when burned in an oxidizing flame. Titanium may produce a purple tint when the clay is burned at a high tempera- 8 66 CLAYS OF MISSISSIPPI. ture. Some black clays are found to be very white after burning. The dark coloring matter in many clays is organic matter which is burned out, leaving the product white. Some yellow or red clays containing an excess of iron may burn to an iron black. The color to which a clay will burn often has an important bearing on its value. A clay which may be of high value as a stoneware clay, for instance, may be entirely useless as a white ware clay, because of the presence of coloring matter which would develop dark shades or splotches during burning. Even in common brick clays the color is of importance. The nearly colorless Milwaukee brick clay is of greater commercial value than the more common red or yellow burn- ing clays. The most satisfactory test to determine the color of the burned product is to subject a sample of the clay to the same conditions of temperature to which the proposed ware is to be subjected. The shades of the burned clay are almost as variable as the natural clay. The oxidation of iron compounds in the clay produces light reds, cherry reds, dark reds, chocolates and iron blacks, the latter being produced by an excessive amount of iron. Clays may contain a considerable quantity of iron and still be white or yellow. Vitrified wares contain iron silicates which may give a green, brown or black color. Spots on white, yellow or red wares are produced by sprink- ling the surface of the clay product with iron or manganese particles. The oxidation or reduction of these particles produce black, br^wn or red specks on the wares. HARDNESS. The property by virtue of which one mineral is able to scratch another mineral is called hardness. Clays are soft rocks. They usually range in the scale of hardness from one to three. The maximum degree of hardness is represented in the flint clays while the minimum degree is attained in the ( halk-like kaolin. This property refers to the ease with which the rock may be scratched. The individual particles in a clay may be a great deal harder than the rock. For instance, the quartz would have a hardness of seven, while the feld spar would have a hardness of six. Kaolinite has a hardness varying from 1 to 2.5. Burnt clay has a much higher degree of hardness than raw clay. Vitrified clay products reach a hardness equal to that of quartz, PHYSICAL PROPERTIES OF CLAYS. 67 which will readily scratch glass. Hardness is a property very essen- tial in all clay wares which are to be subjected to abrasion, as are paving brick; or to compression, as are building brick; or to chemical action, as are sewer pipe. FEEL. Clay containing particles of sand are harsh or gritty to the touch. The grit in some clays may be detected by rubbing the clay between the fingers. In other clays the grit can only be detected by moisten- ing the clay between the teeth. Clays having a large percentage of clay base are smooth to the touch. Kaolin is somewhat like talc or soapstone to the touch. It is a very common practice for people to refer to an unctuous clay or shale as a soapstone. These clays may be shaved with a knife to a perfectly smooth surface, while a clay containing grit will have minute pits upon its surface where the blade of the knife has pulled out the sand grains. The moistened surface of the unctuous clay feels greasy or soapy. As a general rule the gritty clays are the least plastic and are called “lean” or “short” clays, while the more unctuous clays are the more plastic and are called “fat” clays. ODOR. The odor which emanates from the moistened surface cf clay is distinct and characteristic. A very similar odor is given by the surface of some minerals when they are rubbed, and they are said to have an argillaceous cdor. Some clays containing decaying organic matter have a fetid odor. Some very silicicus clays contain such a small amount of clay substance that the argillaceous cdcr is not dis- tinct. Some clays containing a very high per cent of clay substance do not give off an argillaceous odor. Therefore, this property cannot be counted a safe guide to the amount of clay substance. TASTE. The presence of certain soluble salts in clay may be detected by tasting the clay. Common salt, alum and ferrous sulphate are not infreqeuntly detected in this way. Clay prospectors sometimes place clay between the teeth in order to determine its proportion of sandy matter. They also employ this method to determine the texture and degree of plasticity. SLAKING. The crumbling of a clay under the action of water is termed slaking. When a clay slakes it breaks up into small fragments. CLAYS OF MISSISSIPPI. 68 Slaking takes place wherever an air -dried clay surface is exposed to the action * f water. The size of clay fragments or grains into which the clay mass is separated is fairly uniform for the same clay, but varies greatly in different clays. The shape of the particles is variable. Some are flat, some cubical, others irregular. As the particles of the clay separate they absorb water and increase in size. The speed of slaking varies in different clays. Clays of marked density, such as shale and flint clays, slake very slowly while the leaner surface clays slake very rapidly. Wet or puddled clays do not slake as rapidly as air-dried clay to which water is suddenly applied. The speed of slaking is determined by taking samples of natural clays of equal size and placing them in w r ater and by observing the time elapsing until they are completely crumbled. A cube one inch in diameter of a lean loess clay from Grenada, Grenada County, was completely separated in less than ten minutes, while a shale from Mingo, Tishomingo County, was little affected after remaining in water one week. Clays having a high slaking speed are usually very lean or sandy. The loess clays and the more silicious alluvial clays are of this type. The Porter’s Creek (Flatwoods) and the “buckshot” alluvial clays have a slow slaking speed. The Tuscaloosa clays and the Wilcox (La Grange) clays slake rapidly. Clays used for any purpose requir- ing molding without grinding ought to possess at least a moderate slaking speed. A clay possessing a low slaking speed causes less cf time when tempered either in the wet pan or the pug mill. Such clays must be pulverized in the disintegrator and the granulator before they can be tempered and molded. The bottom clay in mest cf the surface deposits of the State has a slow slaking speed, and a ten- dency to form clods, which cannot be entirely removed in the short pug mills in use. For this reason the more successful brick plants are employing the use of one or more forms of pulverizers. PLASTICITY. A clay is plastic when it can be easily fashioned by the hands into a desired form, and when it has the property of retaining that form when so fashioned. Dry clay of any form is devoid of plas- ticity. In order that a clay may become plastic, it must be mixed with a certain amount of water. The quantity of water necessary Plate IV STIFF-MUD BRICK MACHINE OF THE AUGER TYPE. PHYSICAL PROPERTIES OF CLAYS. 69 to plasticity varies with the physical condition of the clay. Not all clays become plastic when mixed with water. This fact leads to the conclusion that some clays possess an inherent property which renders them plastic by the addition of a certain proportion of water. Experi- ence demonstrates that the plasticity of a clay is not due to a single condition, but that it results from the combined action of a group of factors. Some of these factors are well known, such, for instance, as the presence of uncombined water. There are others, however the nature of which is little known. FACTORS OF PLASTICITY. The factors which seem to have the greatest influence upon the plasticity of clay are: 1 . Fineness of Grain. — Some clays which are non-plastic when taken from the pit, slaked and mixed with water, may be made plastic by reducing them to minute particles before mixing with water. In a similar way the plasticity of all clays may be increased. Fineness of grain is not the only essential factor, however. Some clays of exceedingly fine grain may possess but little plasticity. Experiments have been performed with glass, quartz, mica, limestone and talc to determine whether mere fineness of grain was sufficient to account for plasticity. The results were negative in each case. These substances could not be brought to a condition which would permit them to be molded into forms that would retain their shape. 2. The Presence of Uncombined Water. — As has been stated above, a dry clay is not at all plastic but it may become highly plastic when mixed with a certain amount of water. The water acts as a lubri- cant between the clay particles and thereby permits greater freedom of movement. At the same time the surface tension of the water holds the particles and permits a movement of the clay particles with- out interrupting the continuity of the clay mass. An effect to be compared to the stretch of a rubber. 3. The Presence of Combined Water, Bacteria or Some Substance or Condition Which May be Destroyed by Calcining. — When a plastic clay has been subjected to a temperature sufficient to drive off its combined water it is rendered non-plastic. Nor can its plasticity be 70 CLAYS OF MISSISSIPPI. restored by reducing it to fine powder and mixing it with water. This fact proves that some important factor of plasticity has been destroyed by heating the clay. It has been found by practical tests that the plasticity of a clay is increased by “ageing,” “mellowing,” or “curing” the clay. These are terms applied to the same process which consists in storing the clay for a period of time in a damp cool place. For instance clay which has been stored for a time in a damp cellar is found to have an increased plasticity. This increase is thought to be due to the action of bacteria working in the clay. It is found also that the plasticity of a clay may be increased by the addition of tannin or the addition of an emulsion of straw. 4. The Presence of Flat and Interlocking Crystals * — The presence of flat crystals aid by increasing the amount of surface tension of the hydroscopic moisture. This does not apply to the large macroscopic plates of mica which sometimes occur in clay in such abundance as to be detrimental to its plasticity. Crystals which are curved or have angles or serrated edges present interlocking surfaces which increase the tensile strength of the clay and may also increase the plasticity. A number of methods of determining the degree of plasticity of a clay has been suggested, but none are entirely satisfactory. The old method of determination by hand moulding is still the most reliable. FUSIBILITY. Matter may exist in three states, viz., solid, liquid or gas. Water, for example, at ordinary temperatures exists as a liquid. At slightly lower temperatures, it becomes a s^ lid . At higher temperatures, it assumes the furm of a gas. When in the solid state if heat be applied the solid becomes a liquid. This transformation is termed fusion. The temperature at which the solid becomes liquid is called the fusion point of the substance. The fusion point of any substance is controlled by pressure. All solids, having a definite chemical composition under a fixed pressure, fuse at a certain definite tem- perature. This definite temperature is called the fusion point. Ordinary clays, however, are not of definite chemical composition. Clays are composed of a variety of minerals, each having a definite chemical composition and a definite point of fusion. When heat^is ♦See Mo. Geol. Survey, Vol. XI, p. 101* Plate t EITHER-SIDE ROCKER DUMP CAR. PHYSICAL PROPERTIES OF CLAYS. 71 applied to this aggregate of minerals, the one having the lowest fusion point will be the first to fuse. The molten matter which is free to combine may unite with some other mineral or minerals in the clay and form a compound having a lower fusion point than the original compounds. These when molten may act as fluxes for other minerals and the whole clay be reduced to a molten condition at a temperature considerably lower than the fusion point of its most refractory constituents. The change from the solid to the liquid involves the consumption of heat in raising the temperature of the solid to the fusion point. Some heat is consumed as latent heat, some in chemical reactions. Three stages are usually recognized in the fusion of a clay, namely: incipient fusion, vitrification and viscosity (Wheeler). In the first stage the more fusible particles become soft and upon cooling cement together the more refractory particles, forming a hard mass. In the second stage the clay particles become soft enough to close up all of the pore spaces so that further shrinkage is impossible. When the mass becomes cool, it forms a dense solid body which is glassy on a fractured surface. In the third stage, the clay body becomes so soft as to no longer retain its shape, and flows. The fusibility of a clay depends on a number of factors, but the most important ones are the amount and kinds of fluxing impurities in the clay and the fineness of the grain. For determining the temperature of kilns and furnaces and the fusion points of different substances, pyrometers of various kinds are used. One of these is the thermo-electric pyrometer. It consists of a thermo-electric couple which generates an electric current when heated. The intensity of the current increases with the tempera- ture. The current is measured by means of a galvanometer. The thermopile consists of a platinum wire, and a wire composed of 90 per cent platinum and 10 per cent of rhodium. These wires, protected by clay tubes, are inserted into the furnace usually through a small opening in the door. The fusibility of clays is also determined by the use of Seger cones. These cones are made of a mixture of substances of known fusibility. The cones, together with the clay to be tested, are placed in a furnace or oven and the heat applied. The cone which loses its shape at the moment the clay does determines the fusion point of the clay. The cones are arranged in a series as given in the following table: 72 CLAYS OF MISSISSIPPI TABLE 10. COMPOSITION AND FUSING POINTS OF SEGER CONES. No. of Cone 022 021 020 019 018 017 016 Q15 014 013 012 011 010 09 08 07 06 05 04 03 02 01 1 2 3 4 5 r°.i \ 0 .< { {«:; r°j lo.i / 0.5 1 0.5 I 0.5 \ 0.5 f 0.5 Ns 1 0.5 Pt lo.f 5 NAjO.... 5 P 2 0 6 0.5 Na 2 0 0.5 PbO 0.5 Na 2 0 0.5 PbO 5 Na 2 0 5 PbO 5 Na 2 0 5 PbO 5 Na 2 0 5 PbO Na 2 0 PbO Na 2 0 PbO J 0.5 Na t O [0.5 PbO J 0.5 Na 2 0 [ 0.5 PbO 5 Na 2 0 5 PbO I 0.5 Na 2 0 1 0.5 PbO j 0.3 K 2 0 0. [0.7 CaO . 0 . 10.3 K 2 0 0. 1 0.7 CaO 0. j 0.3 K 2 0 0. [0.7 CaO 0. I 0.3 KjO 0. [0.7 CaO 0. I 0.3 K 2 0 0. 1 0.7 CaO 0. I 0.3 K 2 0 0. \ 0.7 CaO 0. 1 0.3 K 2 0 0. 1 0.7 CaO 0. 0.3 K 2 0 0. 0.7 CaO 0. 0.3 K 2 0 0. 0 . 7 CaO 0 . 0.3 K 2 0 0. 0.7 CaO 0. 0.3 K 2 0 0. 0.7 CaO 0. 0.3 K 2 0 0. 0.7 CaO 0. 0.3 K 2 0 0. 0.7 CaO 0. 0.3 K 2 0 0.7 CaO 3 K 2 0 7 CaO Composition 1 AljOj. 2 A1 2 0 3 . 3 A1 2 0 3 . 4-AloOj. 5 A1 2 Os . f 2.0 11 0 I 2.8 S [ 1 .0 B 0 . 55 A1 2 0 3 . 0.6 A1 2 0 3 . 65 A1 2 0 3 . I 3.3 S [ 1.0 E 0.7 A1 2 0 3 . 75 A1 2 0 3 . 0.8 A1 2 0 3 {S: 2 Fe 2 0 3 . 3 A1 2 0 3 .. 2 Fe 2 0 3 . 3 A1 2 0 3 . . 2 Fe 2 0 3 . 3 A1 2 O s . . 2 Fe 2 0 3 . 3 A1 2 O s . . 2 Fe 2 0 3 . 3 A1 2 0 3 .. 2 Fe 2 0 3 . 3 A1 2 0 3 . . 2 Fe 2 0 3 . 3 A1 2 0 3 . . 2 Fe 2 Oj . 3 A1 2 0 3 . . 2 Fe 2 0 3 . . 3 A1 2 0 3 .. 2 Fe 2 0 3 . . 3 A1 2 0 3 .. 2 Fe 2 0 3 . . 3 A1 2 0 3 . . 1 Fe 2 0 3 , . 4 A1 2 0 3 . . 05 Fe 2 0 3 . 45 A1 2 0 3 . 0.5 A1 2 0 3 .. Si0 2 . BO.. 2.2 Si0 2 . 1.0 BO... 2.4 Si0 2 . 1.0BO... 2.6 Si0 2 . 1 .0 BO. . . 2.8 Si0 2 .. BO... 3 . 0 Si0 2 . 1 .0 BO . 3 . 1 Si0 2 . . 1.0 BO... 3 . 2 Si0 2 . . 1 .0 BO... Si0 2 . . BO... 3.4 Si0 2 . 1 .0 BO... 3.5 Si0 2 . . 1.0 BO... Si0 2 . . BO... 3.50 Si0 2 0.50 BO.. 3.55 Si0 2 0.45 BO.. 3 . 60 Si0 2 . 0.40 BO.. 3.65 Si0 2 . 0.35 BO.. 3.70 Si0 2 . 0.30 BO.. 3.75 Si0 2 . 0.25 BO.. 3.80 Si0 2 . 0.20 BO.. 3.85 Si0 2 . 0.15 BO.. 3.90 Si0 2 . 0.10 BO.. 3.95 Si0 2 . 0.05 BO.. r 3.6 1 1 -0 }° 5 A1 2 0 3 . 4.0 Si0 2 . 4.0 Si0 2 . 4.0 Si0 2 . 4.0 Si0 2 . 5.0 Si0 2 . Fusing Point °F 7 °C~ 1.094 1,148 1,202 1,256 1,310 1,364 1,418 1,472 1,526 1,580 1,634 1,688 1,742 1,778 1,814 1,850 1,886 1,922 1,958 1,994 2,030 2,066 2,102 2,138 2,174 2,210 2,246 590 620 650 680 710 740 770 800 830 860 890 920 950 | 970 j 990 1,010 1,030 1,050 1,070 1,090 1,110 1,130 1,150 1,170 1,190 1,210 1,230 Plate VI, MANZ CHICAGO. SWIVEL-DUMPING CLAY CAR. PHYSICAL PROPERTIES OF CLAYS, 73 TABLE 10 — Continued. COMPOSITION AND FUSING POINTS OF SEGER CONES— Continued. No. oj Cone Composition 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 0.3 K 2 0 1 0.7 CaO {o' 3 K 2 0. 7 CaO. 0.3 K 2 0. 0.7 CaO. 0.3 K 2 0. 0.7 CaO. 0.3 K 2 0. 0.7 CaO. 0.3 K 2 0. 0.7 CaO. 0.3 K 2 0. 0.7 CaO. 0.3 K 2 0. 0.7 CaO. 0.3 K 2 0. 0.7 CaO. 0.3 K 2 0. 0.7 CaO. . 0.3 K 2 0. 0.7 CaO.. f 0.3 K 2 0. \ 0.7 CaO.. r o.3 k 2 o. | 0.7 CaO. . 0.7 CaO. 0.3 K 2 0. 0.7 CaO. 0.3 KoO. 0.7 CaO. O. CaO. 0.3 K 2 0. 0.7 CaO. K 2 0. CaO. 0.3 K 2 0. 0.7 CaO. K 2 0. CaO. 0.3 K 2 0. 0.7 CaO. f 0.3 K 2 \ 0.7 Ca f 0.3 \ 0.7 / 0.3 \0.7 r o.3 \ 0.7 r o.3 \ 0.7 |0.6 A1 2 0 3 "1 jo. 7 A1 2 0 3 7.0 Si0 2 J 0 . 8 A1 2 0 3 8.0 Si0 2 . Jo. 9 A1 2 0 3 9.0 Si0 2 . J 1.0 A1 2 0 3 10.0 Si0 2 . Jl.2 A1 2 0 3 . ... 12.0 Si0 2 . J 1.4 ai 2 o 3 14.0 Si0 2 . Jl.6 ai 2 o 3 16.0 Si0 2 Jl.8 A1 2 0 3 18.0 Si0 2 . ^2.1 A1 2 0 3 . . . . 21 0 Si0 2 . 1 2 4 A1 2 0 3 ... 24 0 Si0 2 . 2.7 A1 2 0 3 ... 27.0 Si0 2 . [ 3.1 A1 2 0 3 ... 31.0 Si0 2 . ^3.5 A1 2 0 3 ... 35.0 Si0 2 . 3.9 A1. 2 0 3 39.0 Si0 2 . 4.4A1 2 0 3 44.0 Si0 2 . 4.9A1 2 0 3 49.0 Si0 2 . 5.4 A1 2 Oj 54.0 Si0 2 . 6.0 A1 2 0 3 60.0 Si0 2 . 6.6 A1^0 3 66.0 Si0 2 . 7.2 A1 2 0 3 72.0 Si0 2 . 2.0 A1 2 0 3 200.0 Si0 2 . A1 2 0 3 10.0 Si0 2 . A1 2 0 3 8.0 Si0 2 . A1 2 0 3 6.0 Si0 2 . A1 2 0 3 ..., 5.0 Si0 2 . A1 2 0 3 4.0 Si0 2 . A1 2 0 3 3 .OS 1 O 2 . A1 2 0 3 2.5 Si0 2 . A1 2 0 3 2.0 Si0 2 . A1 2 0 3 1.5 Si0 2 . Fusing Point °F °C 2,282 1,250 2,318 1,270 2,354 1,290 2,390 1,310 2,426 1,330 2,462 1,350 2,498 1,370 2,534. 1,390 2,570 1,410 2,606 1,430 2,642 1,450 2,678 1,470 2,714 1,490 2,750 1,510 2,786 1,530 2,822 1,550 2,852 1,570 2,894 1,590 2,930 1,610 2,966 1,630 3,002 1,650 3,038 1,670 3,074 3,110 3,146 3,182 3,218 3,254 3,290 3,326 3,322 1,690 1,710 1,730 1,750 1,770 1,790 1,810 1,830 f,850 74 CLAYS OF MISSISSIPPI. There are also some recording pyrometers in use. The Bristo recording pyrometer, according to the Iron Trade Review (Nov. 8 1906), consists of three distinct parts, viz., the recorder, which is located at the point most convenient for observation of the records, and for changing of the charts; the thermo-electric couple, the fire-end of which is to be inserted into the space where the tem- perature is to be measured; the leads, consisting of duplex flexible cable for making the electric connection between the records and the fire ends. “The thermo-electric couple, which is located where the tempera- ture is to be measured, produces a current of electricity, which is communicated to the recorder through the connecting leads. This current actuates a face, which is so sensitive that a record may be made upon it with a hair. When applied to the instrument, the chart is supported only over a portion of its surface by a semi-circular plate. The clock movement for revolving the chart is contained in the round case behind the semi-circular chart support, and is pro- vided with an auxiliary attachment for periodically vibrating the unsupported portion of the chart, thus bringing the smoked surface into contact with the pointed end of the recorder arm at intervals of a few seconds. By this means, the record of its position is obtained and friction is eliminated. “The series of marks made by this periodic contact of the recorder arm which removes the carbon from the chart, forms a continuous curve, unless the changes in temperature are extremely rapid. After the record of the day is completed the chart may be removed from the instrument and 'fixed’ by immersion in a fixitive solution, which consists of gasoline or alcohol, to which has been added a small amount of concentrated fixitive. After fixing, the charts may be handled and filed without any danger of destroying the record. “The simplicity of construction insures durability and permanent accuracy and makes the operation of the instrument an easy matter. The protecting case containing the galvanometer is hinged to the back of the recorder. This arrangement prevents injury to the recorder arm while the charts are being changed or the clock wound. “It should be mentioned that the coating of lampblack on the charts is not sufficient to obscure the graduations, and the edges and center are unsmoked. The charts can therefore be conveniently Plate VII. CONICAL CORRUGATED CLAY CRUSHER. PHYSICAL PROPERTIES OF CLAYS. 75 handled and packed for shipment. The couples employed for ranges not exceeding 2,000 degrees Fahr. are made of special alloys, which are inexpensive, and may be of almost any desired form or length to suit the special requirements. For ranges above 2,000 degrees Fahr. the standard Le Chatelier platinum-rhodium elements are used. Compound couples may be used to reduce the high cost of the plati- num-rhodium element. The inexpensive alloys employed for the extension of the couple are such that the two secondary thermo- electric effects at the junctions with the platinum and the platinum- rhodium elements neutralize each other if the temperature at these junctions does not exceed 1,200 degrees Fahr. The indications on the instrument will be the same as if the whole couple had been made of the more expensive metals. Where there are varying temperatures at the cold end of the couple, a mercury compensator is used, which automatically changes the resistance of the circuit, so that no connection is necessary for the working range of the instru- ment.” MECHANICAL ANALYSIS. Clay is a mechanical mixture of mineral particles. These particles vary in size from those which are easily detected by the unaided eye to those which may be seen only by the use of a powerful micro- scope. The mechanical analysis of a clay consists in the separation of these particles into various groups. Because of the extreme degree of gradation in the size of the particles a complete separation is not possible, and it is not essential for the purposes of the clay worker. In the mechanical analysis of soils the following methods of grouping have been employed and the same or similar grouping are applicable, and have been applied, in the separation of clays: TABLE II. METHODS OF GROUPING IN MECHANICAL ANALYSIS. No. of Group Hilgard Hopkins Osborne Whitney Name of Group 1 3.0 m.m. 1 .0 m.m. 3.0 m.m. 2.0 m.m. Fine gravel 2 1.0 m.m. .32 m.m. 1.0 m.m. 1 .0 m.m. Coarse 6and 3 .5 m.m. .1 m.m. .5 m.m. .5 m.m. Medium sand 4 .3 m.m. .032 m. .25 m.m. .25 m.m. Fine sand 5 . 16 m.m. .01 m.m. .05 m.m. .01 m.m. Very fine sand 6 .12 m.m. .0032 m. .01 m.m. .05 m.m. Silt 7 .072 m. .001 m. .005 Clay 8 .047 m. 9 .036 m. 10 .025 m. 11 .016 m. 12 .010 m. 76 CLAYS OF MISSISSIPPI. A number of methods of mechanical analyses has been employed. They may be classified under three heads, viz: the beaker or decan- tation method used by Osborne and others; the elutriation method of Hilgard, and the centrifugal method used by the United States Bureau of Soils. (See Bui. 24, U. S. Agric. Dept.) In the Osborne method of analysis the soil to be analyzed is placed in a cylinder containing water. After being agitated, the suspended particles are allowed to settle until only those of the smallest group remain in suspension. The water is then drawn off and the process is repeated until all the particles belonging to this group have been removed. Then the next larger group is removed. The water is evaporated, the particles dried and weighed and the per cent which they form of the whole determined. All of the groups of finer particles are removed in this way. The larger particles are separated by means of sieves. Hilgard’s elutriation consists of a vertical cylinder containing a rapidly revolving stirrer at the bottom. At the bottom a stream of water is forced through this cylinder at a given velocity. The size of the particles carried out by the current depends on the velocity of the current; i. e., a velocity of 4 m.m. per second is sufficient to carry out all particles of quartz less than 0.25 m.m. in diameter, and a velocity of 64 m.m. per second would carry out particles 2 m.m. in diameter. The elutriatior is used for separating particles larger than 0.01 m.m. in diameter. The finer particles are separated by subsidence. In the centrifugal method, the soil is first disintegrated by the use of a mechanical shaker, an instrument for shaking samples of soil in water, for a period of time sufficient to cause the complete separation of all aggregations of particles. The water containing the suspended particles of soil is then placed in the test tubes of a centrifugal machine. The machine is rotated until all of the coarse particles are thrown down. The particles of the finest group are decanted off. The process is repeated until only the coarser material remains and this is separated by the use of sieves. By the use of a method suggested by Beyer and Williams (see Vol. XIV, Iowa Geol. Sur.) the mechanical analysis of a number of types of Mississippi clays was made with the following results: Plate VIII. HORIZONTAL GRANULATOR PHYSICAL PROPERTIES OF CLAYS. 77 TABLE 12. MECHANICAL ANALYSES OF MISSISSIPPI CLAYS. — Per Cent Fine Coarse Medium Fine Very Fine Silt Clay Formation Locality Gravel Sand Sand Sand Sand Brown loam. . .Jackson 0.0 0.5 0.2 10 5 60 22 Brown loam. . .Yazoo 0.0 0.5 0.3 2 4 75 15 Lafayette . . . . .Newton 0.5 2.0 12.0 53 8 20 5 Flatwoods. . . . .Bradley 2.0 3.0 10 50 13 10 Selma . Starkville. . . 1.0 2.0 4.0 8 9 40 20 Alluvium . Moorhead. . . 0.0 0.2 1.0 2 2 58 30 (Buckshot) Alluvium .Greenwood.. 0.1 1.0 1.5 2 2 42 45 (Buckshot) BONDING POWER. The bonding power of a clay is its power to hold together particles of non-plastic materials. The bonding power of a clay is dependent in a measure on the amount of clay substance which the clay con- tains. It also depends on the size of the grain of the inert matter added. To illustrate, a larger amount of finely divided sand may be added to a clay without decreasing its plasticity and bonding power .than of coarse sand. It is often necessary, in order to secure the proper shrinkage and drying capacity in a clay ware, to use a mixture of two clays or to add sand or grog to the clay. The quantity of the inert matter which may be added without seriously impairing the strength of the ware will depend on the bonding power of the clay. Bonding power is an essential property. TENSILE STRENGTH. The amount of resistance which a clay offers to pull is termed its tensile strength. Wet clays possess this property to a slight degree; dry clays to a greater degree, and burned clays to a still higher degree. Were it not for this property it would be impossible to handle clay ware because of the ease with which they would be cracked or broken. The tensile strength of a clay is not due to any chemical change but to the physical cohesion of its particles. It was formerly thought that the tensile strength of a clay was a safe guide to plasticity, but it is no longer so, for the reason that many very plastic clays have been found to have a very low tensile strength. In preparing clay for the tensile strength test, the clay is first rolled or crushed in a mortar until it is in the condition of a powder. 78 CLAYS OF MISSISSIPPI. Then in order to separate all particles of a certain maximum size, the powder is passed through a sieve. The sieve used in our experi- ments has only forty meshes to the inch. To this powdered clay water was added in sufficient quantity to form a plastic body. The wet clay was then molded in brass molds into brickettes. The form of the mold is seen in Figure 1. Two methods of placing the clay in the molds were tried. In the first the brass mold was oiled and placed upon an oiled glass surface. The clay was then pressed into the mold by the fingers and by the use of a small wooden tamp cut to fit the mold. The clay was cut off on a level with the top of the mold by the use of a putty knife. By moistening the blade of the knife and passing it across the surface of the clay, both surfaces were made perfectly smooth. By the use of the tamp the clay was then pressed out of the mold upon an oiled glass surface. After remaining in this position for a couple of hours the brickettes were placed upon edge in order that both sides might dry equally. This is necessary in order to prevent cracking or warp- ing. This method of molding was found unsatisfactory because of the difficulty in preventing laminations which would weaken the Plate IX REDUCTION MILL PHYSICAL PROPERTIES OF CLAYS. 79 tensile strength of the brickette. Flaws due to air blebs were also produced. By following a method of molding suggested by Orton* better results were obtained. The clay was now wedged into blocks about 3 inches long by 1} inches square. These blocks were now clamped into the molds and patted in until the clay completely filled the mold. The treatment from this point on was the same as in the other method. In the case of every brick prepared in this way the broken section of the brickette was found to be homogenous in structure. A number of clays were tested by both methods. The relative merits of the two methods may be determined from the following comparison of results obtained from tests made on a West Point brick clay. Twelve brickettes molded by the first method varied in tensile strength from 60 pounds per square inch to 151 pounds per square inch and the average tensile strength of the twelve was 144 pounds per square inch. Twelve brickettes molded by the second method varied in tensile strength from 122 pounds per square inch to 181 pounds per square inch and the average tensile strength of the twelve brickettes was 152 pounds per square inch. The form of the brickette is shown in Figure 2. In its longest dimension it is three inches. The cross section of the brickette at the middle, if there is no shrinkage, is one square inch. The shoulders of the brickette have a width of 1 11-16 inches. The thickness of the brickette at any point is one inch, less the shrinkage. After air ♦Transactions of Am. Cer. Soc., Vol. II, p. 110. so CLAYS OF MISSISSIPPI. drying the brickettes were placed in an oven and the hygroscopic moisture driven out at the temperature of boiling water. The brick- ettes were then measured to obtain the amount of shrinkage. The brickettes were tested by the use of a Fairbank’s Cement Machine. The brickettes were placed in the clips of the machine and subjected to a gradually increasing tension. The increase of tension is secured by the weight of shot discharging into the pail cn the lever arm. At the moment of breaking, the discharge of shot is stopped automatically. If the brickettes have undergone much shrinkage, they will not fit the clips of the machine and it will be necessary to bush them. This may be done by placing cardboard or blotter paper between the brickette and the clip. The tensile strength is expressed in pounds per square inch and the shrinkage was calculated and taken into account in estimating the tensile strength of the brickettes. In the majority of tests twelve brickettes of raw clay were tested, and twelve burned brickettes. The average of these twelve tests were taken. The results of these tests are found under the discussion of the physical properties of each clay. TABLE 13. TENSILE STRENGTH OF MISSISSIPPI BRICK CLAYS. Tensile Strength in Pounds per Square Inch Formation Raw Clay Burned Clay Yazoo alluvium (“buckshot” typel 188 484 Yazoo alluvium (sandy type) 90 157 Jackson residual clav 78 112 Lafayette 94 212 Flatwoods (Porter’s Creek) 116 185 Selma residual 133 333 Buhrstone 187 181 Brown loam 78 • 133 The figures given in this table represent the average of a large number of tests made on brickettes molded from clay collected from a great many localities. The individual strength of these clays is given in the discussion of the physical properties of each clay. The brickettes tested in the burned condition were burned at a good red heat, but because of the differences in the clays all of the brickettes were not of equal hardness. Some of them exhibited a lower tensile strength than if they had been burned at a slightly higher tempera- Plate X, DRY PAN PHYSICAL PROPERTIES OF CLAYS. 81 ture. The greater number of brickettes would have been classed as medium; a few were soft; none, however, were hard. POROSITY. A porous clay is one which contains considerable space not occu- pied by clay particles. This unoccupied space is called pore space and its volume depends on the size and shape of the clay particles. The maximum volume of pore space would be reached in a clay con- taining spherical grains of equal size. However, the shape and size of the grains in clays are extremely variable. The quartz grains are usually rounded, water-worn particles, but in some residual clays chey are sharp angled. The mica grains are little flat crystals with irregular edges. The kaolinite may be flat or irregular in shape. The feldspar grains are either more or less rounded or irregular. The grains are in contact only at certain points, thus leaving spac.e*s between the particles. These pores are in connection with other pores, and by a long chain of such connections irregular tubes are formed. These tubes are of capillary size, and the water which is within the clay may pass to the surface by capillarity. Porosity is an important property in clays. The amount cf water required for tempering the clay depends in a large measure on its porosity'. The air-shrinkage of the clay is brought about by the loss of this water. The speed of tempering and the speed of drying depend on the porosity. The larger the pores the more readily the water is taken up and given off CHAPTER IV. PROCESSES OF CLAY MANUFACTURE. MINING. The method of mining clay for use in the manufacture of brick varies with the conditions under which the clay occurs and also with other conditions, such as the capacity of the plant. For example, drilling and blasting may be necessary in the mining of a hard shale, while undermining with pick and shovel may be used to great advan- tage in the mining of many of the incoherent surface clays. Clays are mined either by surface diggings or by underground workings. Underground mining may be conducted by the use of vertical shafts, through which the clay is usually brought to surface by the use of buckets attached by a rope to a windlass. If the clay should outcrop on the side or near the base of a hill, it may be mined by the use of drifts or by the use of tunnels. The different methods of surface mining may be classed as the (1) pick and shovel method, (2) plow and scraper method, and (3) steam shovel method. Pick and Shovel Method . — Usually the full thickness of the clay is exposed at once by digging a pit to the bottom of the clay bed. A sloping entrance to the pit is left on one side to facilitate hauling. If the clay be uniform in quality it is undermined near the base with a pick, causing the clay above to break off and thus securing the aid of gravity in the prosecution of the work. If there are two or more kinds of clay which it is desirable to mix, the upper layer may be removed for a short distance back, then the lower clay undermined. The two clays are thus kept separate and may be mixed in any desired proportion. In some clay pits nearly every spade length in depth represents a change in quality of clay, so that mining may be con- ducted on five or six levels. In many surface clays the upper portion of the bed is so sandy that it may be readily mined with the spade, $4 CLAYS OF MISSISSIPPI. but the’ bottom clay may be a stiff joint clay which will require the use of pick and shovel. Plow and Scraper Method . — The usual method of mining surface clays is by the use of the plow and scraper. The size of the plow and of the scraper, and the number of horses employed, depend on the capacity of the plant. The area of the proposed pit is first plowed and the soil removed. Then it is replowed and the clay taken either directly to the machine or to the mellowing shed, as the case may be, or it is taken to a dump and thrown into a car "which is used to trans- port the clay to a shed or machine. If the clay be uniform, this process of plowing and scraping may continue until the bottom of the clay stratum is reached. It fre- quently happens that there is a marked difference in quality between the clay in the top layers and that in the lower layers of the clay stratum. Under these circumstances the best results may be ob- tained only by mixing the top and bottom clays in certain propor- tions. In order to secure the proper mixture it may be necessary to remove the top layers from a portion of the pit. This top clay so removed may be placed convenient to the machine or the dump, so that it may be used later and the labor of its removal not wholly lost. The clay is now taken partly from the bottom layers and partly from the top in the proportion to give the best results. Usually the sides of the pit are kept sloping, so that the plow may cross the top clay diagonally, cross the bottom clay near the center of the pit and pass across the top clay again at the farther side. Steam Shovel Method . — In plants of large capacity the steam shovel is employed in mining operations. Its use generally means a great economy in labor. The first cost makes it prohibitive for a plant of small size. To operate the steam shovel a track is laid on the bottom of the pit, and the clay scooped from top to bottom of the wall or face of the pit. The clay pit is usually enlarged in a semi-circle. The track upon which the shovel runs is laid parallel with the periphery and advanced as the wall advances. Inside of the steam shovel track is another track for the cars. When the shovel is loaded, a swinging crane moves it over the car. When in the proper position the bottom of the shovel is opened and the clay emptied into the car. The steam shovel of the dipper type has a radius of action of fifteen Plate XI. STIFF-MUD BRICK MACHINE, END CUT. PROCESSES OP CLAY MANUFACTURE. 85 feet and greater. A cut is first made for a certain distance, extend- ing to the bottom of the clay stratum. A track is laid upon the sur- face of the cut, and upon this track the steam shovel is placed. The shovel dips the clay from one bank and delivers it to cars on the opposite side. As the face of the cut advances, the track is moved forward and the clay removed from gradually increasing circles. The clay is well mixed, as the shovel takes clay from all parts of the face at each dip. TRANSPORTATION. A number of methods for the transportation of raw clay from the pit to the machine are employed. These may be classed as (1) wheelbarrow haulage, (2) cart haulage, (3) wagon haulage, (4) scraper haulage, (5) car haulage. Wheelbarrow Haulage . — Wheelbarrows moved by hand power are employed to a very limited extent in some plants. Usually the plants are of small capacity, and the distance which the clay must be moved very short. Some large plants use wheelbarrows to transport clays from storage bins to pug mills. Cart Haulage . — Hauling clay in a cart is not an uncommon way of transporting clays The carts are provided with two wheels, and are strongly constructed. They are usually drawn by one mule, though two mules hitched tandem are sometimes employed. The cart is provided with stout shafts and the harness is arranged so that the shafts may be tilted up and the clay dumped out at the rear end of the cart. This saves the labor of shoveling in unloading. The mule is generally driven by a boy who sits on the front end-board of the cart. The clay digger loads the carts, and a man may be em- ployed to dump the carts as they come to the ring pit or pug mill. This method of haulage is not employed for great distances, and only on comparatively level ground. Wagon Haulage. — Two-horse wagons are employed by some brick manufacturers. They are used where the distance from the plant to the pit is considerable, and the road rough. This is not an eco- nomical form of haulage for a plant of large capacity. Two-horse or four-horse wagons are also employed in transporting clay from railroad cars to the plant. 86 CLAYS OF MISSISSIPPI. Scraper Haulage . — If the clay used is a surface clay and the pit easily accessible to the machine, two-horse drag scrapers may be employed to move the clay. They are also employed for loading the cars used by many plants. . Wheel scrapers are employed in many dry-press plants, in which it is desirable to store the clay in advance of use. Two horses are employed to draw them. The use of the scraper facilitates the mixing of the clay. It is very frequently desirable to mix a plastic clay and a non-plastic clay. A layer of one kind of clay is spread over the floor of the storing shed. This is covered with a layer of the other kind of clay, and the process repeated until the clay reaches the desired height in the shed. In using the clay, a section is taken from top to bottom of the stored clay. This method makes it possible to secure the proper proportion of each clay, and the mixing becomes more thorough in passing through the machinery. The clay gatherer is used in some plants. This is a cylindrical wheeled scraper which gathers the clay and transports it to the plant. Car Haulage . — This form of haulage is used in nearly all plants of large daily capacity. 'The track consists of two parallel lines of wooden, or more often iron, rails of light weight laid on crossties. The rails vary in weight from 12 to 20 pounds, though it is generally not considered economy to use a rail lighter than 20 pound-s, since the car wheels are worn so much more rapidly with the lighter rail. The ties are usually 4 x 4 or 4 x 5, oak or pine pieces. The cars used vary in capacity from one to three cubic yards. Most of the cars now in use have the boxes mounted on pivots so- that they may be swung around and dumped from any position. They may be dumped for- ward, backward or to either side. Selection of Timber for Tracks . — The selection of timber for the ties in the larger plants for the haulage track and the steam shovel track becomes an important matter. It is economy to select the most durable timber for such situations. The durability of ties varies with the conditions. The kind of wood used is one of the determinative factors of its durability. Ex- periments tend to show that under like conditions different woods will last as follows: Plate XII. ROTARY CLAY SCREEN OF THE OCTAGON FORM. PROCESSES OF CLAY MANUFACTURE. 87 TABLE 14. DURABILITY OF DIFFERENT WOODS. Ash, beech and maple 4 years Spruce, hemlock, red and black oaks 5 Elm and long leaf pine 6 Cherry, black walnut, locust and tamarack 7 White oak and chestnut oak 8 Chestnut 8 Black locust, cypress and red cedar 10 “ Redwood 12 FIGURE 3. SIDE-DUMPING CLAY CAR. Decay in wood is produced by the growth of forms called fungi. The conditions favorable to the growth of fungi are (1) abundant moisture, (2) an optimum temperature, and (3) the presence of air. 88 CLAYS OF MISSISSIPPI. The optimum temperature for most species is about 80°F. Fungus decay may be prevented by keeping the timber dry, or at a tem- perature exceeding 100°F., or by immersing in water to exclude the air. Such methods of destroying the conditions favorable to fungus growth are not practicable in the case of ties, and it becomes necessary to resort to some method of excluding the moisture. To accomplish this the timber is first kiln dried and then treated to an immersion in creosote, tar or paint, which prevents the entrance of moisture. FIGURE 4 . DOUBLE-FRICTION HOISTING DRUM. Sap wood decays much more readily and rapidly than heart wood. This fact should be borne in mind when selecting timber for damp places. It should also be remembered that certain species are more durable than others. Timbers are sometimes preserved by steaming to open the pores, and then forcing a combination of bichloride of zinc and of creosote into the pores under pressure. These substances “poison” the wood so that the fungi cannot feed upon it. The lon- gevity of the wood may thus be increased two or three fold. Plate XIII. PUG MILL. PROCESSES OP CLAY MANUFACTURE. 89 GRINDING. Clays are reduced to a pulverulent or granular form by the use of a variety of machines. The following names are applied to such ma- chines: crushers, rolls, disintegrators, granulators, pulverizers, dry pans, ball machines and reduction mills. For some of these to do effective work the clay must be thoroughly air -dried, but some of them may be used for pul verging damp clay. Crushers.- — Jaw crushers are employed for breaking up indurated clays or shales. They contain a pair of movable jaws between which the clay is crushed. These jaws open wide at the top, and gradually close in as the bottom is approached. Another type has a stationery jaw in the shape of an inverted hollow cone in which a conical mova- ble jaw works upon a pivot with an up-and-down movement alter- nately widening and narrowing the space between the jaws. (See Plate VII.) Rolls .— Rolls consist of two or more iron or steel cylinders of rolls between which the clay is crushed. In some machines there are two cylinders which are made to revolve in opposite directions. The clay is fed into a hopper on the upper side of the rolls, and is crushed as it passes between the rolls. In some machines two small cylinders are placed above two large ones. The space between the top cylinders is greater than that between the large ones. The rolls run at different speeds, one having twice or three times the speed of the other. The space between the rolls is regulated by having rubber or coil springs. The distance between the rolls may be regu- lated for different kinds of clay. The rolls are provided with scrapers for keeping them clean. The surface of the rolls may be smooth, corrugated, conical, toothed or conical and corrugated. The capacity varies from 1,000 to 5,000 bricks per hour. The speed of the rolls is ordinarily from 150 to 300 revolutions per minute. Granulators . — Granulators are horizontal, semi-cylindrical shells in which a long shaft revolves centrally. To the shaft are attached knives for cutting and tearing the clay. The angle at which the knives are set upon the shaft determines the speed or movement of the clay through the granulator. The clay is fed into the rear end of the machine, and crushed and shoved forward by the knives. The knives are ground and polished to prevent the clay from sticking. 90 CLAYS OF MISSISSIPPI. The speed of the knives is from 150 to 300 revolutions per minute: The capacity varies from 3,000 to 15,000 brick per hour. Disintegrators .- — Disintegrators may be used for handling dry or damp clay. (See Plate XVI.) TKe machine is provided with a large roller which moves at a low rate of speed, and feeds the clay to a smaller roller which is provided with steel cutters. The cutters may be replaced as they become worn. The disintegrating roller is moved at a high rate of speed, and the cutters strike the clay and break it up. The distance between the rollers is adjusted by moving the feed roller. The speed of the feed roller is 30 or 40 revolutions per minute, while that of the disintegrator roller is from 400 to 600. FIGURE 5 . CLAY DISINTEGRATOR. The combined disintegrator and pulverizer consist of “several oppo- sitely revolving cages formed of round bars, reinforced with iron rings and secured to heavy cast circular discs. The bars of onefset of cages project between the bars of the opposite cages. No grinding or crushing surface is presented ; the material to be disintegrated is received into the inner cage, and by the centrifugal force created by the rapidly revolving cages, the material is projected through the cages and against each other.” This action by force of impact breaks up the clay. The differential speed between the hopper side FIGURE (). PEBBLE CYLINDER MACHINE PROCESSES OF CLAY MANUFACTURE 92 CLAYS OF MISSISSIPPI. and the opposite side is usually about 100 revolutions per minute. The capacity of the machines vary from 1,000 to 10,000 brick per hour. (See Figure 5 and Plate XVI.) Reduction Mills.- Reduction mills are used for grinding dry clay. They consist of a cylindrical chamber with a perforated bottom plate. Above the bottom a perforated grinding plate revolves with a speed of from 300 to 600 revolutions per minute. The clay which is thrown upon the plate furnishes by its own weight the friction necessary for attrition. As the clay is pulverized, it drops through the perforations, or by centrifugal action is thrown out between the rings. (See Plate IX.) Dry Pans. — Dry pans are used for pulverizing dry clays, grog, shales and other hard materials. They consist of revolving pans, containing two large rollers or wheels supported on horizontal axes. The pan is attached centrally to a vertical revolving shaft. The motion of the pan is conveyed to the wheels. The bottom of the- pan in the path of the wheels is solid. The outer portion of the bottom is perforated. The pulverized clay, being thrown outward by centrifugal action, drops through the perforations. Scrapers traversing the bottom of the pan throw the clay in front of the wheels. The pans vary in diameter from 5 to 9 feet. The perforated bottom of the pan is generally made in sections which may be removed, and replaced by sections of different mesh. The wheels or mullers have tires which are removable, and may be renewed when badly worn. The space between the wheels and the bottom of the pan may be adjusted by the aid of springs and adjusting screws. The gearing and pulley shaft are generally placed at the top of the frame, which may consist either of wood or steel, but in large machines the latter is used almost exclusively. The machines vary in weight from two to fifteen tons. Dry pans are sometimes run in pairs, both pans being operated by the same pulley, the latter being on the center of the shaft with a pinion on each end. (See Plate X.) Ball Mills . — Ball mills are sometimes employed for grinding fine grades of clay or glazes. They consist of a cylinder set in a frame, and revolved by means of a driving pulley, attached by appropriate gearing. The clay is placed in the cylinder through an opening in one end of the cylinder. Hard flint pebbles or porcelain balls PROCESSES OF CLAY MANUFACTURE. 93 are put into the cylinder, and as the cylinder revolves these strike the clay and pulverize it. When it has reached the proper degree of fineness, it leaves the cylinder through a perforated plate. In this type of ball mill, the action is continuous. In the periodic type, the clay is put in, and none removed until all has reached the proper degree of fineness. TABLE 15. CRUSHING MACHINERY USED IN MISSISSIPPI BRICK PLANTS. 1. Number of plants using rolls 2 2. “ “ “ “ disintegrators 20 3. “ “ “ “ granulators 15 4. “ “ “ “ dry pans 2 5. “ “ “ “ reduction mills 0 6. “ “ “ “ ball mills 0 7. “ “ “ “no separate crushers 41 Total number of plants reporting 65 SCREENING. Screens are used in few plants in this State outside of pressed brick plants. They are used in order that the pulverized clay may not contain particles larger than a certain maximum size. The perforated materials used in the screen may be either wire netting or perforated iron or steel plates. Screens may be classed as rotary, inclined stationary, inclined vibratory or endless revolving. Rotary Screens . — Rotary screens may be cylindrical, conical cr polygonal. The screens are mounted in strong frames of heavy timber, within which they revolve. Some are provided with a short driving shaft to which a driving pulley is attached by gearing. Others do not have shafts, but the driving pulley is attached by a chain which passes around a cogged -flange on the end of the screen. The screen is mounted on grooved trunions, a pair located at each end of the screen. The cylinders vary in length usually from 5 to 9 feet. The end of the screen opposite the gearing is elevated so that as the screen revolves the clay moves longitudinally through the screen. The tailings, material too coarse to pass through the perforations of the screen, pass out at the end of the screen, and are carried back to the grinder by means of a chute or other form of conveyor. The 94 CLAYS OF MISSISSIPPI. fine clay drops through the screen into a bin below. The rotary screens are kept clean by means of metal brushes or some automatic jarring device. (See Plate XII.) Inclined Stationary Screen . — The inclined stationary screen is in the form of an inclined floor over which the crushed clay passes under the influence of gravity. The inclination of the screen will determine the velocity of the clay and also the maximum size of grain of the screened clay. The lower the velocity of the clay the smaller the size of the largest particle passing the screen. If the screen be placed at a low degree of inclination, more of the clay will adhere to the surface of the screen. Sometimes a steam coil is placed on the under side of the screen to heat the screen, or prevent the clay from sticking to its surface. The pulverized clay drops through the screen into a bin, while the tailings are carried from the end cf* the screen back to the crusher. Inclined Vibratory Screen . — The inclined vibratory screen has a much lower angle of inclination than the stationary, and for that reason requires a constant movement of the screen to aid in the move- ment of the clay across it. The vibratory movements may be either transverse cr lcngitudinal. *“This movement is imparted by either an eccentric or crank. The clay is thrown on the screen, and if the . impulse given to the screen be longitudinal, the clay is gradually carried downwards by repeated little jumps in the directicn cf vibra- tion. If the vibration be transverse, the clay will be thrown from side to side, and will move to the lower end of the screen mere slowly than in the former case. Within limits, the longer the time required for the clay to pass the length of the screen, the more perfectly will the screening be accomplished, and in all instances with this style of screen, the maximum size of the particles passing it is approximately the diameter of the mesh. It is recommended in the use of this class of screen that sufficient play be provided in the vibrating device that a brief pause is allowed at the extremity of each swing. There should be provided solid blocks or posts, against which the screen is brought to a sudden stop with each vibration. The repeated jar thus imparted with each swing is very effective in keeping the | meshes open, especially if the clay happens to be damp.” * Beyer and Williams, Geol. Sur. Iowa, An. Rept. XIV, 1903, p. 180. PROCESSES OF CLAY MANUFACTURE. 95 Revolving Screen . — The revolving screen is made up of a large number of screen plates attached at the ends to two endless chains. The clay is delivered from a spout upon a spreading table from which it descends to the screen. As the screen is revolved, the screen plates move upward to meet the descending clay. The fine particles drop through the perforations in the plates, while the larger par- ticles pass off the end of screen below. The plates are kept clean by a metallic brush-roller which is attached to the lower side of the screen, and removes the clay from the plates as they are brought beneath the frame. Eleven plants in Mississippi, out of a total of 65 reporting, use some form of screen. TEMPERING. Clays are tempered either by the use of soak pit, ring pit, pug mills, wet pans or chasers. Soak Pit . — The soak pit is employed in some soft mud plants. The pit consists of an excavation of rectangular area, into which the clay is thrown. Some pits have bare walls, others are provided with plank walls and bottom. In some plants four or five of these pits are located along a line in front of the drying shed or yard and the molding mac hine, which is placed upon trucks, is moved from pit to pit as the clay in one pit is exhausted. The time required for soaking depends on the texture, and the slaking power of the clay. The clay is usually allowed to remain in the pit at least twelve hours. In case it is to be used for hand molding, it is first “slashed out” with a spade, a process of mixing by hand power. If the clay is to be used in machine molding, it is thrown into the box of the machine where it is pugged before delivery to the molds. The clay and what- ever non-plastic material, such as sand or sandy clay, is necessary, is placed in the pit and then wet down by water conducted to the pit by pipes from barrels, wells or reservoirs. There are not many soak pits used by Mississippi brick plants. Out of 65 plants, only 6 use the soak pit. Ring Pit . — Ring pits are of two types, viz.; those operated by horse power and those operated by steam power. They are similar in form and general make, but differ in size and capacity. They vary in capacity from 8,000 to 30,000 bricks. The pit is circular in 96 CLAYS OF MISSISSIPPI. area and from 2 to 3 feet in depth. The mixer consists of a beam bearing a wheel, the former being attached at one end to a pivotal stake set in the center of the pit. The wheel, which is constructed of iron, has a diameter of about six feet. As the sweep is moved round the ring, the wheel revolves on the beam as an axis, and at the same time moves either outward to the periphery or inward toward the center of the pit, the direction being determined by its position at the start. By means of this alternating centripetal and centrifugal motion, every portion of the pit is traversed by the wheel and the clay thoroughly mixed. The small size pit having a capacity of 8,000 bricks requires a two-horse team for operation. The time required for tempering in the ring pit varies with the clay used. The residual loess clays may be tempered in from two to three hours. These clays, however, slack very readily. With some clays it is necessary to use ring pits, so that the clay which is being tempered one day can be used by the molders the day following. There are 9 plants out of 65 reporting which use the ring pit. These are all operated by horse power. Pwg Mill . — Pug mills are also used for tempering clay. Nearly every brick machine of soft-mud or stiff-mud type contains some provision for mixing the clay. In the soft-mud machine of the vertical type, the clay is pugged in the upper part of the machine, and then forced below into the molds. In the steam-power soft- mud machine a separate pug mill is employed. This consists of a semi -cylindrical chamber, open at the top, in which a horizontal shaft revolves. The shaft is provided with blades which cut up the clay, and mix it thoroughly. The clay enters the chamber at one end, is softened with water, and forced by the revolving blades toward the opposite end of the pug mill, where it is discharged into the molding chamber. The angle at which the blades are set on the shaft determines the speed at which the clay is discharged. For thorough mixing and high speed, the pug mill should be long, so that the clay may come in contact with a large number of blades. Ordinarily pug mills vary in length from 5 to 10 feet. (See Plates XIII and XV.) In stiff-mud machines, sometimes only short pugging chambers are in direct connection with the molding chamber, and the clays are WET PAN PROCESSES OF CLAY MANUFACTURE. 97 tempered and forced through the die by the revolutions of the same shaft. For the majority of clays in use in this State, this form of tempering is not advisable if the pugging is the only form of prepara- tion given the clay before molding. In many plants the pug mill is the only crushing machinery used. It is expected not only to disintegrate the clay but to mix it as well. This cannot be accom- plished in a small pug mill. Wet Pan . — Wet pans are circular pans in which a pair of heavy iron wheels travel. The clay is placed in the pan, softened with water, arid crushed and mixed by the movement of the wheels between the bottom of the pan and the surface of the wheels. Wet pans are not commonly employed in brick plants. They may be employed to advantage in potteries or fire-brick plants. (See Plate XIV.) The “chaser” used in some potteries consists of a wooden or iron wheel which revolves in a circular path on a floor and crushes and mixes the clay. TABLE 16. SUMMARY OF TEMPERING MACHINERY USED IN MISSISSIPPI BRICK PLANTS. Number of yards using soak pits 6 “ “ “ “ ring pits 9 “ “ “ “ separate pug mills 17 “ “ “ “ wet pans 0 “ “ “ “ chasers 0 “ “ “ “ no separate tempering machinery 33 Total number of yards reporting 65 MOLDING. Clay which is molded into brick may be used as a soft mud, a stiff mud, as dry or semi-dry clay. The methods of molding clays into brick may be classed according to the following grouping: Soft -mud process. Hand molding. Machine molding. Horse power. Steam power. Stiff-mud process. Plunger type mac Auger type machi Repressing brick. Dry press process. Hydraulic power. Steam power. 98 CLAYS OF MISSISSIPPI. In some plants two or more methods of molding are employed. They may manufacture soft-mud brick, stiff-mud brick and dry- pressed brick. Very few clays are adapted to all methods of manu- facture. A sandy type of clay is better adapted to the soft-mud FIGURE 7 . HORSE-POWER SOFT-MUD BRICK MACHINE. process. A more plastic clay can be used to better advantage in a stiff -mud machine. It is possible in many clay pits to secure a variety of clays, so that mixtures may be made which will permit the use of all three methods of molding. Plate XV. MAN| SOFT-MUD BRICK MACHINE AND PUG MILL. PROCESSES OF CLAY MANUFACTURE. 99 Soft-mad Process. Hand Molding . — The tempered clay is taken from the soak pit or the ring pit and loaded on a wheelbarrow by the use of a spade. The wheelbarrow is then run to the molding table, which usually stands on the drying floor. The drying floor is a level and smooth tract of land which is covered with a thin coating of sand. The molding table is now sprinkled with water and then with sand, and the clay transferred from the wheelbarrow to the table. The off -bearer takes a molding frame which contains six molds, and dipping it first in water and then in sand, places it on the table in front of the mclder. The molder takes a mass of clay, rolls it, and kneads it. He then drives it by a sudden downward stroke into a mold. This is repeated until the six molds are filled. The clay is stroked from the top of the mold by the use of a wire stretched between the points of a bow. The surplus clay cut from the top of the molds is called “caps,” and is thrown back on the table to be used again. The off-bearer takes the molding frames and empties them upon the drying floor. After drying for a few hours the bricks are turned upon edge, a process called edging. After remaining upon the drying floor from twelve to twenty-four hours the bricks are laid in loose piles, a process called “hacking.” Hacking the output of the pre- ceding day allows the use of the same drying floor for the new day’s run. Then it makes it possible better to protect the brick from rain, because of the limited space which they now occupy. When they are piled up canvas or boards may be used to cover them. In some yards the molding tables are moved along between racks in which the brick are placed upon pallets. As soon as the sections on each side of the table are filled with brick-loaded pallets the table is moved to the next section. One man can mold 8,000 bricks in a day of ten hours, but in most plants from 5,000 to 6,000 is consid- ered a day’s work. In one plant one man molds and places in the rack 6,000 bricks, for which he receives $1.50 per day. Machine Molding— According to the power used molding ma- chines may be classed as horse-power machines and steam-power machines. The horse-power machine consists of an upright rectan- gular box in which a vertical shaft supplied with arms turns by means of a sweep. The sweep is attached to the shaft near the larger 100 CLAYS OF MISSISSIPPI. FIGURE 8. BRICK MOLD SANDING MACHINE. PROCESSES OF CLAY MANUFACTURE. 101 end of the former, the projecting heavy end of the sweep being used as a counterpoise. The horses are hitched to the small end of the sweep and travel in a circular path around the machine. The clay is thrown into the opening at the top of the machine, and after being thoroughly mixed or pugged by the arms in the upper part of the box, is worked to the bottom and pressed by plung- ers located near the bottom of the shaft into the molds. The molds are generally held in wooden frames, there being six molds to a frame. The molds are passed under the machine at one side, become filled fr m the press box and are taken out on the other. By moving a lever the filled frame is thrown out and an empty one inserted beneath the press box. They may not be completely stroked as they leave the machine, so that it may be necessary to use a wire or paddle to remove remaining clay. The molds are first dampened and then sanded. The use of the sand is to prevent the clay from sticking to the molds. The more plastic the clay the more tenaciously it clings to the molds. The molds may be sanded by shoveling sand into the molds, shaking it about and then tossing it out. The mold -sander is a machine constructed for the purpose of saving labor in sanding molds. It consists of a frame which rotates in a cylinder. The molds are placed in the frame, and by the rota- tion of the latter the molds are forced through a bed of sand in the bottom of the cylinder. Some of the soft-mud horse-power machines are placed upon low trucks and moved from soak pit to soak pit as the clay is used. Ma- chines of the horse-power type have a capacity of from 8,000 to 15,000 bricks per day of ten hours. Soft-mud machines of steam power have a capacity ranging from 18,000 to 35,000 bricks per day. For a machine of the latter capacity five men and three boys are required at the machine. Three off -bearers are required if no car system is used ; if a car system is used one off -bearer can handle the output of the machine. Indurated clays and clays of high plasticity cannot be used with economy in the soft-mud process. In this State only the sandy type of surface clays is used. The residual clay covering the loess is molded in a large number of plants by the soft-mud process. The Selma residual is not generally successfully used in the soft-mud process unless there is considerable sandy clay present for mixing. 102 CLAYS OP MISSISSIPPI. There are sometimes nearby deposits of Lafayette which may be used for tempering the clay. The alluvial clays of the Yazoo basin have been used for the manufacture of soft-mud brick. The sandy type of clays is best adapted to the soft-mud process. The “buckshot” clays adhere to the mold, shrink excessively and are difficult to pug. Stiff-mud Process. The machines used in the stiff-mud process of molding are of two types, a vertical machine, in which the clays are pressed into the molds by the action of plungers, and an auger machine, which may be either vertical or horizontal. Plunger T ype Machine . — The plunger machine is provided with a revolving wheel which contains the molds. As the wheel revolves clay is pressed into some of the molds by descending plungers, then as the plungers are lifted, the bottom of the mold rises and forces the molded brick out. Thus a portion of the wheel passes under the machine and a portion is in the open and forms the delivery table. The pugging chamber is usually directly above the molds. Just enough water is added to the clay to form a stiff mud. The molded brick are in a condition to permit handling without danger of much loss, whereas a soft -mud brick would first require a certain amount of drying. Auger Type Machine . — In the vertical auger type machine the clay is forced by an auger to the base of the machine. From this point the clay is forced through a rectangular die. The size of this die may be either the same size as the cross section of a brick or the same size as a horizontal section, The clay which is forced through the die forms a bar of clay which is usually strong enough to retain its shape under considerable strain. After the clay is tempered it is placed in the small pugging chamber in which there turns a vertical shaft. At the top this shaft is provided with small blades for pug- ging the clay. The lower part of the shaft is provided with an auger, which catches the clay forced downward by the pugging blades, and presses it through the die. The friction of the bar of clay against the die may cause the edges of the bar to break and curl, forming serra- tions. The clay may lack cohesive power, in which case more bonding material should be added. 104 CLAYS OF MISSISSIPPI. Various substances are employed to decrease the amount of fric- tion between the steel die and the clay bar. Steam under high pressure may be forced in around the bar in the die. Kerosene or lubricating oil is often employed as a lubricant in some plants and soap suds in others. The surface of the bar is sometimes coated with sand as it leaves the die, to facilitate handling and hacking without injury. The spiral motion of the auger, the friction of the clay against the surface of the auger, producing smooth clay surfaces, and the differential velocities in the bar of clay produced by friction of the die, all cause laminations in the clay. In the horizontal auger type of stiff -mud machine a horizontal shaft works in a cylindrical pugging chamber, and supports at the end opposite the die short blades which pug the clay and force it to the auger, by which it is in turn forced through the die. In the multiple-bar type there are two or more dies through which the clay is forced, thus forming as many parallel bars of clay. As the clay issues from the die it is carried by a belt across the cutting table, where it is cut into bricks. The cutters are either “side-cut” or “end-cut.” Where the side-cut is employed the width of the bar is the length of the brick, and where the end-cut is employed the width of the bar is the width of the brick. The cut surface of the brick in the former is on the side of the brick, in the latter on the end of the brick. Side-cut brick dry more rapidly than end-cut brick, because of the greater area of cut surface which is more porous than the die-puddled surface. Some cutters are operated by hand, others are automatic. There are two automatic side cutters in general use. One is the rotary, consisting of a wheel provided with wire spokes. By the rotation of the wheel these wires are passed through the bar of clay at regular intervals, the movement of the bar being co-ordinated with the rota- tion of the wheel. The other side cutter is the oscillating, reciprocal cutter, which consists of a frame between the projecting points of which wires are stretched. The wires are separated by the thickness of a brick. These wires, by a lateral or downward movement, are forced through the bar. During the time of cutting the bar is mov- ing forward and the cutter has a reciprocal movement. PROCESSES OF CLAY MANUFACTURE. 105 The end cutter consists of a revolving wheel, the spokes of which are bifurcate near the ends, having wires stretched between the points of the bifurcations. As the wheel revolves the wires are forced through the bar of clay cutting it into brick lengths. As the bricks leave the cutter they are caught by the off -bearing belt, which moves at a greater velocity than the bar of clay, and soon separates the brick. The brick are taken from the off-bearing belt and placed upon cars or pallets for transportation to the dryer. Repressing Brick. Stiff-mud brick or soft-mud brick after molding are often pressed in a machine called the “repress.” The repress consists of a steel mold box into which the brick are placed and subjected to strong pressure. The hand repress (see Fig. 10) consists of a heavy iron frame supporting a steel mold box, which is provided with a remov- able top and a movable bottom plate, which is forced upward against the brick in the mold. The pressure exerted by the movable bot- tom (plunger) is obtained by throwing back the lever. When the top is removed and the lever thrown back, the repressed brick is forced to the top of the mold. These represses have a weight of from 700 to 900 pounds and a capacity of from 2,000 to 3,000 brick per day. The larger represses are operated by steam (see Plate XVIII). They generally have two molds and have a capacity of from 10,000 to 25,000 brick per day. They vary in weight from 5,000 to 9,000 pounds and exert a pressure of 4,000 or 5,000 pounds per square inch. The pressure may be applied by plungers from above or by plungers both above and below. The brick from a stiff-mud machine may be taken immediately to the repress. Soft-mud brick must dry to about the consistency of stiff-mud brick before repressing. There is an advantage to be gained in allowing stiff-mud brick to dry a little before repressing, as in that case defects of drying may be partly obliterated. The principal things to be gained by repressing are: (1) An in- crease in the density of the brick. The clay particles are brought closer together and their union is more perfect. This diminishes the porosity of the brick and decreases its absorption power. (2) A partial destruction of laminations and serrations. Stiff-mud brick CLAYS OF MISSISSIPPI FIGURE 10 . HAND-POWER REPRESS BRICK MACHINE. PROCESSES OF CLAY MANUFACTURE. 107 are often serrated on the edges. The auger also produces a lami- nated structure. Both of these structures may be at least partly obliterated by repressing. (3) The surfaces of wire cut brick are often rough. This roughness may be destroyed and the surface of the brick made smooth by repressing. (4) The form of the brick may be improved by repressing and its strength increased. The edges of the brick which may have been rounded in the die are shaped. Indentations are removed. (5) Any desired name, design or mark may be imprinted on the surface of the brick. FIGURE 11 . SIX-MOLD DRY-PRESS BRICK MACHINE. Dry-press Process. In the dry-press process the clay is first reduced to a powder in a disintegrator or pulverizer. It is then screened to remove all particles larger than one-sixteenth of an inch in diameter. The air- dried clay is then pressed into molds with a pressure sufficient to cause the particles to adhere so firmly that the brick may undergo without crumbling all of the handling that raw clay brick usually have to endure. The dry -press machine (see Figure 11) consists of a heavy steel frame containing a press box and a delivery table. The molds 108 CLAYS OF MISSISSIPPI. (usually four to six) are filled with clay by a charger which is con- nected with the clay hopper by a canvas tube. When filled with clay the charger glides forward over the molds, filling them with clay. Then as the charger returns to be refilled the plunger descends and forces the clay into the mold. At the same time the bottom of the molds are pressed upward and thus the clay is subjected to two pressure movements. As the plunger rises the bottom of the molds continues to come up, thus forcing the brick out of the molds to a level with the surface of the delivery table upon which they are pushed by the next forward movement of the charger. The surfaces of the molds are heated by steam in order to prevent the clay from sticking. To prevent the imprisonment of air in the brick, holes are made in the press plates to allow its escape. The clay used by the dry -press machine is generally placed in a storage shed and allowed to mellow for a few weeks, or in some plants months before it is used. Under the mellowing process capillary moisture becomes more thoroughly distributed, the clay lumps are softened and the reduction to the powdered state rendered easier. In case two or more kinds of clay are used, the mixing may be done thoroughly by placing them in the storing shed in successive layers. In using the clay a vertical section of the deposit is taken. Storing a large quantity of clay in the shed during favorable weather makes it possible for the plant to continue operations during unfavorable weather periods. The dry pressed brick may be taken directly from the press and placed in the kiln. The expense of drying is avoided. Because, however, of the density of the brick the water-smoking period is longer than in the soft -mud or the stiff-mud brick. TABLE 17. METHODS OF MOLDING MISSISSIPPI BRICK. 1. By soft mud process. a. Number of plants using hand power 11 b. “ “ “ “ horse power 2 c. “ “ “ steam power 7 2. By stiff mud process. a. Auger type, end cut, single die 19 b. “ “ “ “ double die 2 c. “ “ side cut, single die 6 d. Plunger, vertical type 7 3. By dry-press process 11 Total 65 Plate XVI. CLAY DISINTEGRATOR. PROCESSES OF CLAY MANUFACTURE. 109 DRYING. When brick are brought from the molding machine they contain the water necessary for tempering the clay. Before they can be burned this water must be removed. It must be removed so grad- ually as not to impair the strength or appearance of the brick. This process of water removal is called drying. In the following pages are presented some of the fundamental facts upon which the removal of water from clay is dependent. Principles of Drying. Humidity is the condition of the atmosphere with respect to its water-vapor content. The total amount of moisture that the air is capable of containing at any given temperature constitutes the capacity of the air at that temperature. The capacity of the air varies with the temperature. The air is said to be saturated when the amount of water vapor which it contains is equal to its capacity. The amount of moisture actually present in the atmosphere is termed its absolute humidity. The relative humidity is the ratio of the absolute humidity to the capacity of the atmosphere. For example, air at a temperature of 50° F. has a capacity of 4 grains per cubic foot. Suppose, however, the air at this temperature contained but 2 grains of moisture per cubic foot. The' absolute humidity of the air is 2 grains per cubic foot and its relative humidity is the ratio which 2 grains (absolute humidity) bears to 4 grains (capacity), which is one-half or 50 per cent. Air which has a relative humidity as high as 80 per cent is considered moist air. If the relative humidity is below 50 per cent the air is called dry air, and its humidity is low. The capacity of the air depends upon its temperature. The higher the temperature of the air the more moisture it can contain. Air at a low temperature might be considered damp though it con- tains just the same amount of moisture as air which, at a higher tem- perature, would be considered dry. For example, air at 50° F. has a capacity of 4 grains per cubic foot. Now, if the air at that temperature contained 3 grains per cubic foot it would be considered moist air, since its relative humidity is 75 per cent. Now let the same air be raised to a temperature of 100° F., and it now has the capacity of approximately 20 grains. 110 CLAYS OF MISSISSIPPI. But the relative humidity is now only 15 per cent, and it is an exceed- ingly dry air. Water is lost from a wet body by evaporation. Evaporation is the transfer of moisture from one area to a less humid area. Such transference does not take place between two saturated bodies, but between a saturated body and a non-saturated body. Water may pass from a wet surface to the surrounding air, provided the air is not saturated. Evaporation is produced through the vibration of molecules, which causes some of those at the surface to fly off into space. The vibration of the molecules is produced by heat, and the higher the temperature of the water the more rapidly the mole- cules separate. Evaporation takes place from the surface of ice, but it takes place much more rapidly from the surface of water at the boiling point. At this point the vapor tension is equal to the pressure of the atmosphere which it will displace. At the point of evaporation water assumes the form of a gas, and expands to 1,700 times its liquid volume. When the surrounding air contains all of the vapor it can hold it is saturated. The point of saturation depends on the temperature of the vapor. TABLE 18. NUMBER OF GRAINS OF SATURATED WATER VAPOR IN A CUBIC FOOT AT VARIOUS TEMPERATURES. 10 ° .776 34 ° 2.279 58 ° 5.370 82 ° 11.626 12 ° .856 36 ° 2.457 60 ° 5.745 84 ° 12.356 14 ° .941 38 ° 2.646 62 ° 6.142 86 ° 13.127 16 ° 1.032 40 ° 2.849 64 ° 6.563 88 ° 13.937 18 ° 1.128 42 ° 3.064 66 ° 7.009 90 ° 14.790 20 ° 1.235 44 ° 3.294 68 ° 7.480 92 ° 15.689 22 ° 1.355 46 ° 3.539 70 ° 7.980 94 ° 16.634 24 ° 1.483 48 ° 3.800 72 ° 8.508 96 ° 17.626 26 ° 1.623 50 ° 4.076 74 ° 9.066 98 ° 18.671 28 ° 1.773 52 ° 4.372 76 ° 9.655 100 ° 19.766 30 ° 1.935 54 ° 4.685 78 ° 10.277 102 ° 20.917 32 ° 2.113 56 ° 5.016 80 ° 10.934 104 ° 22.125 Water evaporates more rapidly into a vacuum than into space filled with air, but at a given temperature the same quantity of water will evaporate into each. A mixture of air and water vapor has a greater expansive power than air alone. If to a cubic foot of dry air weighing 516 grains at a temperature of 80° F., 11 grains of water vapor be added by evaporation, the whole mixture will weigh but 510 grains. Then its density is less than the original air. Plate XVH ROTARY AUTOMATIC BRICK CUTTER, PROCESSES OF CLAY MANUFACTURE. Ill Brick are dried by evaporation of water which they contain. When taken from the mold, brick contains water in two forms, viz., the water which has been added for tempering, and hygroscopic moisture. The former passes readily from the clay at ordinary temperature; the latter can only be expelled at the temperature of boiling water. It is the water which is absorbed from the atmos- phere, and is present in all clays except those kept in absolutely dry air, and is the water which is removed from brick in the process of water-smoking. The object to be obtained in drying brick is the economical and rapid removal of water without impairing in any way the quality of the brick. The tenacity with which moisture is held by clays varies. As a rule the finer the grain of the clay constituents, the more slowly it gives up its water. Since clay is as a rule finer in grain than sand, the higher the amount of clay the greater the diffi- culty of drying. Since plasticity is affected by these conditions, the higher the degree of plasticity the more difficulty encountered in drying. A very sandy clay will dry rapidly, but it may be weak because of the small amount of bonding material. When the brick are taken from the machine, they have the same temperature as the surrounding atmosphere. If they are put in a dryer which has a higher temperature, they begin to lose moisture rapidly as the tem- perature of the dryer is raised. But since clay absorbes heat slowly, if the temperature of the dryer is too high, the outside of the brick may become dry before the inside becomes hot. This produces differential shrinkage, the outside of the brick contracting more than the inside. The results of such differential contraction is the cracking or checking of the brick. The more plastic the clay, the more care must be exercised in drying. The remedy lies in the very gradual increase in the temperature of the brick. In many of the steam dryers now in use, a “dead chamber” is used for heating the brick to the temperature of the first chamber of the dryer. The “dead chamber” is a closed division of the dryer into which steam is turned, there being no means of circulation, or at least very little. The brick do not dry, but become heated thoroughly by the steam. When they reach the temperature of the air at the beginning of the dryer, they are run into the first chamber of the dryer, and are then in a condition to pass through the dryer rapidly. 112 CLAYS OF MISSISSIPPI. Since air is the medium through which the water is removed from brick, the drier the air used the greater its drying capacity. The air used in an artificial dryer must be taken from the atmosphere, therefore, the amount of moisture that enters a dryer on a given day will depend on the humidity of the atmosphere. Beyer and Williams* make a calculation of the amount of heat necessary to evaporate the water contained in 1,000 brick. The subject is treated as follows: “Clays vary a great deal in the quantity of water required for tem- pering. Since tempering water only is removed in the dryer, the amount which it is necessary to evaporate in drying also varies. As an average, it may be said that clays worked by the plastic process contain 22 per cent of water. For one thousand brick, this means in the neighborhood of 1,700 pounds of water to evaporate in drying. A dryer tunnel containing twelve cars each loaded with five hundred standard bricks must pass enough air to carry out over five tons of water frf>m these brick. It thus becomes a problem for investigation to determine for a given dryer the most saving conditions under which this water can be removed. “In open air drying, the currents of air which carry away the water are warmed by the sun’s heat. The specific heat of air is .2374. A cubic meter (1 .308 cu. yds.) of air weighs 1 .293 kilograms at 0°C. and 760 mm. barometric pressure. The heat contents of each cubic meter of air at zero degrees is, therefore, 1.293 times .237= .306 kilogram calories. At any higher degree, its contained heat would be, L29 - t,mes \ i n which a is the coefficient of expansion = .00367 and t the observed temperature. If we assume an average summer heat of 16 C. (most out of door drying being done in the summer), it is seen by the formula that the heat content of a cubic meter of air is 4 . 631 units, which shows an average of essentially .3 heat units for each degree of temperature. These heat units are taken up as latent heat by the water in drying and as a consequence the temperature of the air is lowered. This means that for every degree the air is cooled, it loses .3 of a unit of heat. The measurable heat of water and the latent heat of water vapor formed at ordinary temperatures may be taken as 611 heat units, i. e., to evaporate one kilogram of water at 16 C. requires 611 heat units; .3 units, therefore, ( 3 gms -) will evaporate at this temperature only .491 of a gram. *Iowa Survey, Pages 239—243, Rept. for 1903. STEAM-POWER DOUBLE-MOLD BRICK REPRESS, PROCESSES OF CLAY MANUFACTURE. 113 “We have already assumed an average of 1,700 pounds (772 + kgms.) of water per thousand brick. To evaporate 772 kilograms of water requires 611 times 772 = 471,692 heat units. To dry a thousand brick, therefore, with air at ordinary temperature, requires that 1,572,301 (772,000+. 491) cubic meters of air lower one degree in temperature to furnish the required amount of energy. Or, where the air is somewhat confined as in drying sheds so that it may remain in contact with the wet ware for some time, the same evaporative power would be possessed by one-half the volume lowering two degrees, or by one-tenth lowering ten degrees and so on. “Whether or not drying actually approaches in efficiency these theoretical figures depends largely on the humidity of the air. Air near its saturation point gives up its heat much less readily and will consequently take up water more slowly than comparatively dry air. Rapidity of movement of the currents of air also influence their drying capacity. As a general thing, very little change of temperature is ever’actually noticed in outside drying, but the drying depends largely on the air circulation. The more rapidly this takes place, the more air is brought in contact with the clay and conse- quently drying progresses more speedily. “In closed chamber dryers the conditions are different from those discussed in several particulars. The air no longer circulates of itself but a draft must be produced to move it. The heat for drying is not contained in the air as it enters from the outside, but must be supplied to it artificially. Both movement of the air and heating it requires the expenditure of energy which is not necessary in out of door drying. Of the heat supplied to the air, it is clear that not all is utilized in the evaporation of water; for this air leaves the dryer at a higher temperature than it enters, thus carrying out considerable quantities of sensible heat. Likewise, the brick enter the dryer at atmospheric temperatures and leave it at much higher temperatures. These are the chief sources of waste of heat in the dryer and are in turn briefly treated. “On leaving a drying chamber, one cubic meter of vapor-saturated air at 30° C. consists of . 958 cubic meter of dry air and . 042 of water vapor ( 7 6 o ‘ ), where 31.6 is the tension of aqueous vapor. “The .958 cubic meter of dry air can hold the following heat units : = 7.935 heat units. 114 CLAYS OF MISSISSIPPI. “When this same dry air entered the dryer at, say, 10° C., it had a volume of r+ 70036 7 ^ 30 - 10 ) = -893 cubic meters. “This volume of air could carry as it came into the dryer 1.293 X. 893 X.237X 10° _ o co n i 4 , i+. oo 367 xio — = 2 • heat units. “The amount of heat taken out of the dryer, therefore, in each cubic meter of air under the assumed conditions is 7.935 — 2.639 = 5 . 296 heat units. “The above result is obtained on'the assumption that the air on issuing from the dryer is completely saturated. This is seldom if ever true. Its degree of saturation or relative humidity may be ascertained in any instance and the value used in the formula. As- suming for example that the outgoing air is but half saturated, which is ordinarily more nearly the case, similar calculations to the above will show that at 30° C. 8,108 heat units will be carried out per cubic meter of saturated air. At 10° the same air carries in 2.696, making a loss in this case of 5.412 heat units. If each cubic meter passing through the dryer causes a loss of 5.412 units of heat, the total loss per each thousand brick is 56,610 heat units. “In the same manner may be calculated the loss of heat incurred by bringing the air into, and removing it from, the dryer at any observed temperatures. “We have seen that at these low temperatures 611 heat units are required for the evaporation of each kilogram of water. As has been shown, to remove the water from 1,000 brick (772 kgms.) requires 471,692 heat units. And since each cubic meter of air at the highest temperature, 30° C., can evaporate 13.55 grams of water, to dry 1,000 brick takes 772X13.55 or 10,460 +cubic meters of air. “Seger gives the following formulae for the calculation of the capacity of chimneys. In their practical application these expres- sions may be used for determining the dimensions of a stack for circulating an amount of air, at the temperatures of operation, which is found necessary to remove the water from a given amount of clay in the time required to dry it. “V=628 = velocity of air in meters per minute and, 1 f V = 3 - 14 * 6d ~y = volume of air in cubic meters per minute. PROCESSES OF CLAY MANUFACTURE 115 steei/'rack car for transporting brick on pallets. FIGURE 12 . 116 CLAYS OF MISSISSIPPI. “In these formulae: “t — t 1= the temperature difference between the shaft of the chimney and the outside air, '“d = the diameter of the chimney at its mouth, “h = the height. “The clay as it enters the drying chamber has the temperature of the atmosphere and as it leaves carries out considerable quantities of sensible heat. The specific heat of clay is about .2. The heat carried out is calculated by the weight of the ware, or, M, multiplied by .2 (t — t 1 ) where t — t 1 = difference in temperature of the brick at entrance and exit. One thousand brick contain on an average 7,700 pounds, 3,500 kilograms, of dry clay. Under the conditions assumed above, 3,500X .2 (30 — 10) 14,000 heat units per thousand brick. “We have now obtained the amount of heat used in the evapora- tion of water from 1,000 brick, 471,692 heat units; that taken out as sensible heat in the escaping half-saturated air, 56,110, and the heat dissipated by the clay itself, 14,000 heat units. Total energy necessary to dry 1,000 brick, neglecting radiation, is, therefore, 542,302 units of heat. “This energy is supplied in artificial dryers by the combustion of fuel. The average Iowa coal furnishes 6,700 heat units per kilo- gram. To dry a thousand brick requires the consumption, therefore, of, in round numbers, 81 kilograms, or 178 pounds of coal. “By carrying out similar calculations to the above for a range of temperatures and different degrees of humidity, it may be shown that (1) economy can never be obtained unless the air is removed very nearly saturated. The rule in this regard is, therefore, to remove the air only after it has taken up practically all the water vapor it can hold, and before dew is deposited. (2) Economical drying in closed compartments can be had only at temperatures above 50° C. (122° F.), and below 100° C. (212° F.), when the air is removed as nearly saturated as possible. The amount of heat carried out by the air rises rapidly as the humidity decreases; and as the temperature of drying is lowered the ratio of heat loss to that actually used in the evaporation of water increases rapidly.” PROCESSES OF CLAY MANUFACTURE. 117 Methods of Drying Brick. Brick dryers may be classed as open air dryers, and artificial dryers. The former may be further subdivided into (a) open yard dryers, ( b ) rack and pallet dryers, and (c) shed and hack dryers. The latter may be classed as (a) hot floor dryers, (b) chamber dryers, and (c) continuous tunnel dryers. Open Yard Dryer .— This system of drying is used in soft-mud plants. The brick are placed on pallets from the mold. The loaded pallets are taken by the off -bearer to a sanded, open yard where they are emptied by inverting them. After drying a little, the brick are placed on edge to allow both sides of the brick to dry equally, and to prevent cracking of the upper surface due to unequal drying. After drying from 12 to 24 hours, the brick are hacked on the yard until the air drying is complete. The hacking makes it possible to handle a larger number of brick per yard, and at the same time makes it possible to more easily protect the brick in case of rain. The principal objections to this system of drying arise from the great amount of labor required to handle the brick, and the high per cent of loss sustained in inclement weather. The source of energy for the evaporation of the water is from the sun. There is no means of controlling the form of energy in the open yard. And it is impossible to control the circulation of the air and thus check the removal of moisture. Rack and Pallet Dryer . — This system is used for both soft-mud and stiff-mud brick. The racks are covered with A-shaped roofs and generally open at the sides and the ends. Some, however, are provided with temporary walls consisting of movable plank, canvas, or burlap. Soft-mud brick are placed on pallets. Each pallet holds one mold full of brick, usually six. Where the brick are molded by hand, it is the practice to move the molding table along between the racks, filling them section by section. Where a machine is used for molding, the brick are carried by hand, wheelbarrow or car to the racks. In some yards a rack car is used, and the loaded pallets are transferred from the car to the racks by an elevating movement of the car. Usually in stiff -mud plants, the brick are packed upon large pallets as they are taken from the table. The pallets contain from 118 CLAYS OF MISSISSIPPI. 200 to 500 bricks. These pallets are transferred by elevating cars to racks or to sheds as the case may be. Considerable loss may be experienced in case no protection is provided for the racks in the way of side walls. Dashing rains may beat upon the brick. Currents of air may cause cracks by too rapid extraction of moisture from the exposed sides of the brick. The length of time required for drying is dependent on the conditions of the weather. In a dry atmosphere the brick may dry in a few days, whereas under humid conditions it may require weeks. Shed Dryer . — Some plants are provided with large sheds with low supports or racks made in rows with car tracks between for the purpose of receiving the pallets with the hacked brick. In others no supports are used ; the pallets are placed upon the floor or the brick hacked upon the floor without pallets. The brick are criss- crossed so that there is free circulation of air between them. The percentage of outside exposed brick is less than in the use of the rack and pallet and consequently the per cent of loss is less. The protection from storms is more efficient in the use of sheds. The cost of construction, however, is somewhat higher for the sheds. As in the case of the open yard, the source of energy for evaporation is from the sun for these last two mentioned dryers. The air currents, however, can be controlled. There is not the necessity of economizing in the volume of air that becomes imperative in the use of the steam or hot air dryer. Artificial Dryers . — There are numerous forms of dryers which utilize either directly or indirectly heat derived from the combustion of fuel. Some of these dryers consist of a brick or metal floor under which fires are built. The clay ware to be dried is placed on the heated floor. In other floor dryers the floors consist of wooden strips which are heated by means of steam coils placed beneath the floor. This last form of dryer is commonly used for drying sewer pipe, drain tile, hollow blocks and terra cotta. For drying brick two types of artificial dryers are in common use, the chamber dryer and the continuous tunnel dryer. The former consists of one or more rooms or chambers into which the brick are placed. Commonly the brick are hacked upon cars and the cars run into the dryer. The heat is furnished from steam pipes Plate XIX B. HAND MOLDING AND STARTING A SCOVE KILN, HOLLY SPRINGS, PROCESSES OF CLAY MANUFACTURE. 119 laid beneath the track. In some dryers pipes are also placed along the side walls or even along the roof. Under the track is considered the most advantageous position for the pipes. As the air in the chamber becomes heated it expands, rises and takes up moisture from the moist brick. The moist air is taken out through one or more chimneys or through a large wooden stack. The air is con- ducted from chamber to chamber by means of flues. In the continuous tunnel dryer the heat supplied is increased as the distance from the entrance to the tunnel increases. The increase in heat may be obtained by increasing the number of sections of steam pipe. The brick are placed upon cars, which are run into the dryer from the stack end of the tunnel. They are gradually forced through the tunnel in the direction of increasing heat and decreasing moisture. The dried brick are taken out of the tunnel at the end opposite the stack. Hot air used in drying brick may be obtained by utilizing the waste air in burning pottery or by heat produced in the burning of fuel. The air heated directly by the combustion of fuel is forced through the tunnel by means of a fan placed at the end opposite the dryer. The air heated by the furnace is drawn into a chamber where it loses its soot. After passing to the fan it is forced to the mixing chamber to be mixed with cold air. From the mixing chamber it is conducted to the dryer. BURNING. Burning is a term which is applied to that part of the process of brick manufacture during which the raw clay product is subjected to high temperatures. These high temperatures bake the clay. Hence the burning of brick is not at all analogous to the burning of wood or coal. The clay is not consumed but its moisture is expelled, its density and hardness are increased, and its plasticity destroyed. The changes which take place are partly chemical and partly physical. Brick are first hardened by drying in the sun. The use of sun- dried brick dates back probably to 8000 B. C. Such brick are still used for building purposes in some arid or semi-arid regions. Burned brick were first used about 4500 B. C. The process of burning consists of two periods, the water-smoking period and the burning period. The object of water-smoking is to 120 CLAYS OF MISSISSIPPI. evaporate the water in the clay, and for this purpose the temperature of the kiln is maintained at about 212° F. The production of too high a temperature may result in cracked brick from stresses set up by steam. The air which enters the bottom of the kiln soon becomes laden with moisture. Unless this moisture is removed, it may be condensed in some cooler portion of the kiln. The water thus formed upon the surface of the brick may soften them or produce kiln white. The moisture-laden air should be removed as rapidly as possible. At the beginning of the water-smoking period, a large amount of air should be allowed to enter the kiln, and be maintained until the ware is dry. As the temperature of the kiln increases, the amount of air may be gradually diminished. Wood is generally used for water-smoking, and it should be dry. The firing should be so con- ducted as to produce a slow fire and little flame. Hard wood and coke are said to give the best results. During the burning process, the temperature should be increased slowly until the temperature has reached 932° F. to 1,112° F., at which temperature the water of crystallization is driven off. After that, the temperature may be increased more rapidly until the point of incipient fusion is reached. The temperature may then be main- tained until the heat has reached the center of the ware. Care must be exercised at this stage of the process, because in some clays the difference between incipient fusion and viscosity may not be very great. In some parts of France, Belgium and England, brick are burned in the open by mixing the fuel and the raw brick. However, in most plants, the brick are burned in kilns. Types of Kilns. Brick kilns may be classed according to the following outline: Up-draft kilns. A. Scove kiln. B. Dutch or clamp kiln. Down-draft kilns. A. Beehive kiln. B. Rectangular kiln. C. Continuous kiln. Plate XX. B. SHED DRYER, BRICK HACKED ON GROUND. PROCESSES OF CLAY MANUFACTURE. 121 UP-DRAFT KILNS. In the up-draft kilns, the heat passes through the brick in the kiln from the bottom toward the top. In the down-draft kilns, the heat is conducted through flues to the top of the kiln and from there it passes downward through the brick and is withdrawn through flues at the bottom of the kiln connected with stacks. Scove kiln . — The scove kiln is the simplest type of kiln and because of its cheapness is much used in small plants. The brick are set in a rectangular mass and surrounded by a double wall of soft-burned brick. The outer surface of the wall is coated with mud in order to prevent loss of heat and the entrance of air. The fire boxes are made by setting the brick in the kiln in such a way as to form arches, which extend through the kiln from side to side. The fuel is placed in these arches from openings in the side walls. The top of the kiln is covered with a layer of brick laid flatwise and close together. The platting, as this layer is called, is sometimes partly or wholly covered with sand or clay, and the heat is directed by moving this loose material from point to point. The brick are protected frcm the weather during the setting and burning by a shed roof raised upon poles, which extend several feet above the top of the brick. The brick are laid in from 40 to 50 courses. Scove kilns are employed mostly for burning common brick. Vitrified brick are not easily burned in them because of the difficulty of securing a high temperature. They are not suitable for seme kinds of clay for a similar reason. Dutch or clamp kilns . — The Dutch cr < lamp type of up-draft kiln is in more common use than the scove kiln. These kilns have per- manent side walls of a thickness sufficient to retain mere heat than the scove kiln. It is possible to secure a higher temperature in them. The brick are stacked within the walls of the kilns, arches being left and the top platted as in the case of the scove kiln. In the up-draft kiln several courses of brick at the bottom are likely to be overburned, while the top courses are underburned. The brick in the arches are generally slaggy, brittle and discolored. The percentage of hard burned brick varies with the care exercised in burning. Rarely more than 70 per cent of the kiln may be classed as number 1 brick. 122 CLAYS OP MISSISSIPPI. DOWN-DRAFT KILNS. In down-draft kilns the fire boxes are outside the walls, and the heat is conducted to the top of the kiln, and after passing through the brick is drawn off by flues at the bottom through one or more stacks. Some of the advantages of this type of kiln are: (1) labor saved in platting; (2) heat more thoroughly and completely dis- tributed ; (3) no extreme heat in contact with brick ; (4) small amount of waste due to misshapen brick, because the highest heat is at the top where there is the minimum weight. From a single burn in this type of kiln as much as 90 per cent of hard burned brick has been obtained. Beehive Kiln . — The beehive kiln is a circular down-draft kiln with an oval top. The kiln is supplied with one or more stacks. The gases are taken to these stacks from the bottom of the kiln by means of flues. It is essential that the kiln should have a uniform draft, and this is secured by construction of flues and arrangement of the wares within the kiln. The capacity of such kilns varies from 25.000 to 75,000. Rectangular Kiln . — The down-draft rectangular kilns are of various types. They range in capacity from 150,000 to 300,000. They may be supplied with one large stack, into which more than one kiln may r pen. Each kiln may be supplied with two or more small stacks. The stacks are placed either at the side or end of the kilns. Continuous Kilns . — Continuous kilns are built with the object of using the waste heat from the cooling brick to water-smoke the un- burned brick. In shape they may be circular, oval or rectangular. The only one used in Mississippi is rectangular in form. It con- sists of 12 chambers arranged in two rows and separated by perma- nent walls. Each chamber has a capacity of 70,000 brick. Pro- ducer gas is used as fuel. The gas is conducted by conduits from the gas producer to the various chambers. The waste heat from the chamber in which the burning has just been completed is used to water-smoke the one which has just been filled. The transfer of waste heat may be made between any two of the twelve chambers. The gases and water from the chambers are taken through the flues to one large stack, located near the end of the kiln. CHAPTER V, FUEL. Fuel may exist as a solid, a liquid or a gas. Among the various substances used for producing heat are included wood, sawdust, straw, bagasse, turf, peat, lignite, bituminous coal, cannel coal, an- thracite, coke, charcoal, petroleum, furnace oil, shale oil, creosote, tar oils, natural gas, coal gas, water gas, gasoline gas, naphtha gas and producer gas. The principle combustible elements contained in these fuels are carbon and hydrogen. In the process of combustion these elements are oxidized. The carbon (C) unites with oxygen (0) in the propor- tion of one part of carbon to two parts of oxygen, if enough of the latter is present, otherwise one part of each combines, forming in the first case carbon dioxide (C0 2 ), in the second case carbon monoxide (CO). The hydrogen unites with oxygen in the proportion of two parts of hydrogen to one part of oxygen, forming water (H 2 0). Both of these chemical unions result in heat. The number of heat units produced varies with different sub- stances. The heat -producing power of a pound of various sub- stances is given by Parsons in “Steam Boilers,” as follows: TABLE 19. CALORIFIC VALUE OF DIFFERENT FUELS. Hydrogen gas 62,032 Carbon to carbon dioxide 14,500 Carbon to carbon monoxide 4,400 Carbon monoxide to carbon dioxide 4,330 Olefiant gas 21,344 Liquid hydrocarbons (oils), varying with weight 19,000 to 22,600 Charcoal, from wood 13,500 Charcoal, from peat 11,600 Wood, dry average 7,800 Wood, 20% moisture 6,500 Peat, dry average 9,950 Peat, 20% moisture 7,000 Coal, anthracite, best quality about 15,000 Coal, anthracite, ordinary 13,000 Coal, bituminous, dry 14,000 Coal, cannel 15,000 Coal, ordinary poor grades 10,000 124 CLAYS OF MISSISSIPPI. CLASSES OF FUELS. Wood. Wood is composed of organic and inorganic matter and water. The first is combustible, the others are non-combustible. In the process of burning the water is vaporized. The organic matter is consumed, i. e., it is transformed into invisible gases. The inorganic matter remains in the ashes. When wood has been dried at 300° F. it contains about 99 per cent of organic matter and 1 per cent of inorganic matter. The organic matter consists of carbon, 49 per cent; oxygen, 44 per cent, and hydrogen, 6 per cent. When wood is heated above the temperature necessary to drive off its moisture, gases are generated which ignite, producing flame. The amount of heat produced depends upon the moisture condition of the wood. When thoroughly dry a given amount of pine will produce just as much heat as the same amount of hickory. Pine, however, produces more flame than oak or hickory, and not as good a bed of live coals. Under ordinary yard conditions the oak or hickory may be said to exceed the pine by 25 per cent in the pro- duction of heat. Wood under ordinary conditions contains 25 pounds of water, 74 pounds of wood and 1 pound of ash for every 100 pounds. The wood portion consists of 37 pounds of carbon, 4.4 pounds of hydrogen and 32 pounds of oxygen. In the process of combustion 4 pounds of hydrogen unite with 32 pounds of oxygen, forming water. This leaves about half of the wood substance, 37 pounds of carbon and .4 pounds of hydrogen, as elements of combustion. One hundred pounds of green wood contains about 50 pounds of water. This wood is capable of producing 270,000 heat units. A heat unit is the amount of heat required to raise one pound of water one degree Fahrenheit. The same amount of wood containing 30 pounds of water will produce 410,000 heat units. Air-dried wood contains about 20 per cent of water, and 100 pounds of such wood is capable of producing 500,000 heat units. When the same amount of wood contains only 10 per cent of water it will produce 580,000 heat units. One hundred pounds of kiln-dried wood, containing 2 per cent of water, will produce 630,000 heat units (Bull. 10, U. S. Forestry Div., 1895). FUEL. 125 These facts point clearly to the desirability of having on hand a good supply of wood, so that the use of green or even half-dried wood may be avoided. The wood should not be decayed nor should it be wet or green if the highest heating efficiency is to be obtained. The moisture in the wood must be converted into water vapor and a great deal of heat is consumed in this conversion. Many of the brick plants of the State rely entirely upon wood for fuel. Nearly all use wood for water-smoking. Oak and yellow pine are the more common kinds used, but in some plants ash, gum, wil- low and other species are used. The price of wood generally varies with the abundance of accessible timber and the ccflidition of the local labor market. The average price per cord paid for wood is two dol- lars. The maximum price paid is two dollars and eighty-five cents, and the minimum is one dollar and twenty -five cents. Coal. Varieties of Coal . — There are a number of varieties of coal, rang- ing from nearly pure vegetable fiber in peat to the highly carbonized and crystalline anthracite. The names applied to these varieties are peat, lignite, cannel coal, jet, bituminous coal, semi-anthracite and anthracite. These coals vary in the amount of carbon and hydrocarbons which they contain and in other constituents. Peat .— Peat is an accumulation of vegetable matter which is thought to represent the first stage in the formation of coal. It is generally brownish-black in color and of light weight. It contains from 50 to 60 per cent of carbon, 5 or 6 per cent of hydrogen, and from 35 to 40 per cent of oxygen. Its fuel ratio is only .47 as compared with 28 in some anthracite coals. It is formed from the accumulation of vegetable matter in bogs and low marshy areas. A great deal of peat is being formed in glacial lakes and ponds by the growth of spagnum moss. Lignite . — On account of its low stage in the period of coal devel- opment lignite is sometimes called “green” coal, but because of its color it is also called “brown” coal. It is usually brown or brownish black in color. Some varieties on fresh fracture present a shiny surface. It generally disintegrates rapidly when exposed to the air and breaks up into small cubes or laminae. It is supposed to repre- 126 CLAYS OF MISSISSIPPI. sent a more advanced stage in the development of coal than peat. It contains less volatile matter than the latter and more fixed carbon. Its fuel ratio is about 1.50. It usually contains from 35 to 45 per cent of fixed carbon; from 5 to 20 per cent of ash, and from 25 to 30 per cent of hydrocarbons. Bituminous Coal . — Bituminous coal is a soft coal more dense than lignite, and represents a more advanced stage in coal formation. It is of a deep black color and frequently has a rather distinct resinous luster. It burns with a smoky flame. When exposed to the air it does not disintegrate as readily as lignite and contains a higher per- centage of fixed carbon. Its fuel ratio is more than double that of lignite. Bituminous coal contains from 65 to 85 per cent of carbon, about 5 per cent of hydrogen, and about 15 per cent of oxygen. Its specific gravity varies from 1.20 to 1.40. Bituminous coals may be divided into two varieties, coking and non-coking. Coking coals when ignited with air excluded may be changed to coke. Anthracite . — Anthracite is the hardest form of stone ccal. It has a sub-metallic luster and breaks with a conchoidal fracture. It is brittle and of a shining black color. It has a specific gravity of from 1.57 to 1.67. It has a low percentage of hydrocarbons and a high per centage of fixed carbon. For this reason it is difficult to ignite and burns without much flame. It has a high calorific value and when burned under the proper conditions produces an intense heat. Its fuel ratio may be as high as 28. It contains from 90 to 95 per cent of carbon. The per cent of hydrocarbons is from 3 to 5 per cent. Anthracite coal represents the last stage in coal metamorphism and has lost all traces of its vegetable origin. Determination of the Calorific Value of Coals . — In the determination of coal constituents moisture, volatile and combustible matter, fixed carbon and ash are determined by weight; sulphur, iron and phos- phorous by analysis. The value of any substance as a fuel is usually found by determining the power of a given quantity of the substance to evaporate water. The heat-producing power of a substance is termed its calorific value. The calorific value of a fuel may be ob- tained by determining the number of pounds of water which it will convert into steam at the boiling temperature of water under a pres- sure of one atmosphere by the consumption of one pound of fuel. FUEL. 127 The calorific value of fuels may be determined by the calorimetric method, the computation method and the direct method. In the calorimetric method a definite amount of fuel to be tested is burned in a chamber surrounded by a definite amount of water. The rise of temperature of the water is registered by a thermometer. The proportion of the fuel to the water used is one part of fuel to every 967 parts of water. This proportion is used because when water is converted into steam at 212° F., 967° F., or 537.22 gram degrees or calories of heat, disappear as latent heat. If the tempera- ture of 967 parts of water be raised one degree, enough heat has been employed to convert one part of water into steam at 212° F. Thus the rise of temperature of the water as recorded by the thermometer will indicate the number of parts of water capable of being converted into steam by the heat produced by the fuel. In testing coal by the calorimetric method it is reduced to a fine powder in order to secure perfect combustion. Since the fuel must be consumed in a closed vessel it is necessary, in order that its com- bustion^may be complete, to add compounds which will supply oxygen. To furnish the oxygen supply the coal is mixed with potassium chlorate (KCI0 3 ) and potassium nitrate (KN0 3 ). The coal is con- sumed in a copper cartridge which fits into a cup-shaped receiver. A second copper cylinder with a valve tube at the upper end is placed over the first. A row of openings around the lower end of the second tube permits the escape of gases which are produced in the combus- tion. This apparatus is placed in a graduated glass cylinder which contains the water. The charge in the tube may be ignited by the use of a fuse of sufficient length to permit the apparatus to be placed in the vessel before the charge is ignited, and to cause ignition to take place by the time the apparatus reaches the bottom of the vessel. The charge may be ignited by means of an electric current. The gases of combustion pass through the entire column of water and therefore their heat is lost to the water. The rate of combustion of the charge should be controlled so as to prevent too rapid evolu- tion of gases, and at the same time the rate of burning should not be so slow as to cause loss of heat through radiation. The rate of com- bustion may be regulated by tamping the charge or by varying the amount of the oxygen-producing substances. As soon as the charge has been consumed the stopcock of the cartridge is opened so that 128 CLAYS OF MISSISSIPPI. the water may come in contact with all parts of the cartridge and extract its heat. To facilitate extraction the furnace may be moved up and down in the water. The temperature of the water should be taken before the charge is burned and at the close of the burning. The temperature of the water should always be lower than the tem- perature of the room. Allowances must be made for heat absorbed by the gases of com- bustion, for heat produced by the decomposition of the oxygen com- pounds, for the loss of heat by radiation and conduction, and for heat absorbed by the apparatus. The total loss of heat from these sources is from 10 to 15 per cent. By means of the chemical analysis of coals and the use of the fol- lowing formula, the calorific value of a coal may be computed: Total heat expressed in B. T. U. = 14,500 C + 62,032 (H— ^). The C is carbon, H is hydrogen and the O oxygen contained in the coal. They represent the amount by weight of each of these sub- stances. The atomic weight of hydrogen is 1, the atomic weight of oxygen is 16. When they unite to form water they unite in the pro- portion of two H to one O or 2 to 16 (1 to 8). When present in the form of water they do not produce heat, hence J of the oxygen is subtracted from the hydrogen. Another formula sometimes used is, total heat = 14,600 C + 62,000 (H-^) + 4,000 S, in which S repre- sents the amount of sulphur present. In the direct method of determining the calorific value, fuel is used to evaporate water under normal power plant conditions, and an accurate account of the number of pounds of coal used and the number of pounds of steam produced is kept for a definite period. In this way the evaporative power of different fuels may be deter- mined and compared. Since no coal is mined in Mississippi all our industrial plants are dependent upon other States for this class of fuel. Different parts of the State use coal derived from different sources. Some of the States from which our coal supply is drawn are Pennsylvania, Illinois, Indiana, Missouri, Arkansas, Tennessee, Kentucky and Alabama. We have very little information as to the calorific value of these different coals. The information given in the following table has been collected by Professor Albert Barnes, of the Mechanical Depart- ment of the Agricultural College of Mississippi. The tests were all made on Alabama coals: FUEL. 129 TABLE 20. CALORIFIC VALUES OF ALABAMA COALS. Name of Coal. Kind of Coal. Length of test in hours. i Weight of coal burned in pounds. Weight of ash. Weight of water evaporated. Weight of water evaporated F. and A. 212° F. Weight of water evaporated | per unit of coal. Cost of evaporating 100 pounds of water. 1 Sterling L. Lanier, Agt R. of M. . 7 4,577 579 21,411 21,460 6.00 $0.02025 Gilnath Coal Co Corona Coal Co. (Annie R. of M. . 7 6,419 537 38,352 40,001 6.2 .0195 Mae Mine) Carbon Hill coal(Kan- R. of M. . 7 4,487 1,012 29,571 6.9 .0178 sas Mine) Hill Creek Coal Co. R. of M. . 4 1,379 275 9,462 9,944 7.2 .0167 (Birmingham) R. of M. . 8 5,603 6,236 311 34,250 45,968 6.417 .0195 Carbon Hill Tenn. Coal, Iron & R. of M. . 12 47,990 7.7 .0153 R. R. Co Lump . . . 10 5,642 486 47,514 49,604 8.7 .0150 Hill’s Creek Coal Co . . R. of M. . 18 13,386 11 99,730 7.73 .015925 Tupola Coal Co R. of M. . 4 2,833 17,600 20,768 7.33 .0187 R. of M. — Run of Mine. Mississippi Lignites. As stated in the foregoing pages no coal is mined in Mississippi, and, to the best of our present knowledge, we have no coal other than lignite. There are numerous beds of lignite occurring in the Wilcox strata of the Eocene and in some other horizons. Below is given the analysis and the calorific values of a number of these lig- nites. The samples were ’collected by Dr. Calvin S. Brown of the State Survey and the determinations were made under the direction of Dr. W. F. Hand, State Chemist. TABLE 21. COMPOSITION OF MISSISSIPPI LIGNITES. Constituent No. 10 No. 14 No. 15 No. 20 No. 43 No. 46 Moisture .. 11.61 14.20 11.40 13.20 12.20 12.62 Volatile matter. . . , . . 34.61 35.24 32.61 40.16 46.27 40.85 Fixed carbon . . 42.47 41.80 37.00 31.24 30.86 39.94 Ash . . 11.31 8.76 18.99 15.40 10.67 6.50 Total . . 100.00 100.00 100.00 100.00 100.00 100.00 Sulphur 2.66 .63 1 .50 1 .20 • 76 2.05 5 130 CLAYS OF MISSISSIPPI. CALORIFIC VALUES. Calories per gr 5595 5255 5112 5050 5096 5392 B. T. U. per pound. . 10071 9450 9201 9090 9173 9706 COMPOSITION OF THE ASH FROM LIGNITES. Constituent No. 14 No. 23 No. 25 No. 43 No. 46 No. 48 Silicon dioxide 29.10 22.95 63.65 51.82 35.00 22.66 Aluminum oxide — 13.45 12.37 13.25 26.98 17.00 14.88 Iron oxide 21.00 19.00 10.95 7.12 29.00 20.62 Calcium oxide 22.80 21.37 2.50 6.07 4.55 15.20 Magnesium oxide. . . .19 .97 .90 .22 1.50 2.90 Sulphur trioxide .... 8.53 14.70 4.46 5.45 6.34 19.89 Oil. Mineral oils are now used for fuel in many industries. Petroleum is said to be used successfully in the burning of brick in some of the oil fields of the West. The oil is kept in tanks and fed into the fire box by means of an injector-nozzle. The blast from the nozzle pro- * duces a current of air which mingles with the oil and flame in the combustion chamber, thereby aiding combustion. Petroleum, or crude oil, is a liquid of complex composition. It is composed largely of a mixture of hydrocarbons. There are two general classes of petroleum, viz.: those having a paraffin base and those having an asphaltum base. Chemically petroleum is composed of carbon, hydrogen and oxygen. The percentage of carbon varies from 82 to 87 per cent; hydrogen from 12 to 14.8 per cent, and oxygen from 1 to 6 per cent. The specific gravity ranges from .80 to .983. A gallon of petroleum weighs from 6.5 to 7.8 pounds. A pound of oil will produce from 19,000 to 22,000 heat units and will evaporate from 19.6 to 22.7 pounds of water. The results obtained from the use of petroleum for boiler fuel at the World’s Fair at Chicago in 1893 were as follows: TABLE 22. AMOUNT AND COST OF PETROLEUM FOR BOILER FUEL. Consumption of oil per hour Water evaporated from 212° F. into steam at 125 pounds, per pound of oil Equivalent evaporation from and at 212° F Cost of oil per hour .' Cost of oil per boiler horse-power per hour Cost of labor per boiler horse-power per hour Cost of boiler horse-power per hour 22,792 pounds 14.25 14.88 $56.20 .0057 .0006 .0063 FUEL. 131 Repeated experiments seem to have demonstrated that in evapo- rative power one pound of oil is equivalent to two pounds of coal. The causes of the superiority of oil are summed up by Parsons in Steam Boilers as follows: “1. The combustion of the liquid fuel is complete, whereas that of coal is not, consequently in the former case there is no lost heat in smoke or soot. “2. There are no ashes or clinkers, and consequently no fires to clean with the accompanying loss of heat and drop in the steam- pressure. “3. The boiler-tubes are always free from soot and clean, and therefore always in the best condition for transmitting the heat from the gases passing through them to the water of the boiler. “4. The temperature of the escaping gases may be considerably lower than is required to create the draft necessary for coal-firing. “5. The admission of air being under complete control, and the fuel being burned in fine particles in close contact with oxygen of the air, only a small excess of air above that actually necessary for the combustion of the fuel is required. With coal, in order to insure as complete combustion as possible, a very much larger excess of air is required.” Gas. Natural gas has not been discovered in appreciable quantities in Mississippi or in the territory immediately adjacent. For this reason this form of fuel is not used in any of our industrial plants. Artificial gas, called producer gas, is used in one of the clay plants of the State for burning its ware. The gas is manufactured by injecting steam upon a bed of burning soft coal. The gas is used in a chambered continuous kiln. By the use of this form of fuel there is said to be a large saving in labor and fuel. Twenty-six hundred feet of natural gas is equivalent, in heating power, to a good average ton of coal. It would, however, require 100,000 feet of some of the poorer artificial gases to be of equal value. The composition of natural gas and some of the artificial gases is given in the following table from Kent’s Mechanical Engineer’s Pocket-book: 132 CLAYS OF MISSISSIPPI. TABLE 23. COMPOSITION OF FUEL GASES. Constituent CO H CH 4 C2H4 C0 2 N O Vapor Weight in pounds of 1,000 cubic feet Heat units in 1 ,000 cubic feet 1 Natural Coal Water gas gas gas 0.50 6.0 45.0 2.18 46.0 45.0 92.60 40.0 2.0 .31 4.0 .26 .5 4.0 3.61 1.5 2.0 .34 .5 .5 1.5 1.5 45.60 32.0 45.6 100,000 735,000 322,000 Producer-gas .4 nthracite Bituminous 27.0 27.0 12.0 12.0 1.2 2.5 .4 2.5 2.5 57.0 56.2 .3 .3 65.6 65.6 137,455 156,917 The same author gives the following fuel values for the different kinds of gaseous fuels: TABLE 24. FUEL VALUE OF GASES. No. of heat Cost of No. of heat units in Average 1,000,000 units in furnaces cost heat units 1,000 after per obtained Kind of gas cubic feet deducting cubic in used 25% loss foot furnaces Natural gas 1,000,000 750,000 Coal-gas, 20 candle power 675,000 506,250 $1.25 $2.46 Carburetted water-gas 646,000 484,500 1.00 2.06 Gasoline-gas, 20 candle power 690,000 517,500 .90 1.73 Water-gas from coke 313,000 234,750 .40 1.70 Water-gas from bituminous coal. . 377,000 282,750 .45 1.59 Water-gas and producer-gas mixed 185,000 138,750 .20 1.44 Producer-gas Naphtha-gas, fuel 2} gallons, per 150,000 112,500 .15 1.33 1,000 feet Coal, $4.00 per ton, per 1,000,000 306,365 229,774 .15 .65 heat, units utilized .73 Crude petroleum, 3 cents per gal- lon, per 1,000,000 heat units. . .73 CHAPTER VL PROPERTIES OF BRICK. EARLY HISTORY OF BRICK* According to present historical knowledge clay was first employed for structural purposes in Babylonia.* This country is partly an alluvial plain bordering on the Persian Gulf. The plain is drained by the Tigris and the Euphrates rivers and is probably very similar in origin to the Yazoo basin of the Mississippi. This plain, like others of its kind, is devoid of ledges of hard rock which can be used for structural purposes. So the early inhabitant, not finding the rock with which to construct his house, was compelled to employ a sub- stitute. Hence brick — another proof that necessity is the mother of invention. Down beneath the drifting sands of the plain the early inhabitant of Babylonia found a plastic clay which he .could mold and fashion into brick. Thus brick and other clay wares were manu- factured, probably 8,000 years before the beginning of the Christian Era. The first brick were irregular rectangular masses of clay dried in the sun. Brick were not burned until about 4500 B. C. The first burned brick were small, flat upon one side and rounded upon the other, or plano-convex brick with rounded corners. These brick were set upon edge in the wall, the spaces being filled in with mud or bitumen. Forty-five varieties of these early brick have been discov- ered in excavations recently made in Bismya. BRICK TESTS. In order to determine the wearing qualities of brick a series of tests is employed. These tests determine the amount of load required to break the brick crosswise, transverse strength; the amount of load required to crush the brick, crushing strength; the number of pounds of pull the brick will stand, tensile strength; the ♦Banks, Clay Products of Early Babylonia, Clay Worker for January, 1907. 134 CLAYS OF MISSISSIPPI. amount of water the brick will absorb, absorption test; the amount of knocking about required to destroy the brick, impact test; and the amount of freezing the brick will stand without deterioration. These tests are not so essential in small buildings, but in large structures, and especially in paving work, they are very essential. However, only four are considered of leading importance, viz.: transverse strength, crushing strength, impact strength, absorption. Crashing Strength. The crushing strength of a brick is expressed in the number of pounds of pressure per square inch of surface that a brick will stand. The object of the test is to determine how much load the brick are capable of supporting when placed in a wall. The crushing strength of brick varies from 500 pounds to 15,000 pounds per square inch. The weight of an ordinary brick is about 5 pounds. When laid flatwise a standard brick has an exposed top area of 32 square inches. Each brick laid upon this surface exerts a pressure of about i of a pound per square inch. Every six bricks then exert a pressure of 1 pound per square inch. Therefore, in a wall 100 feet high the pressure exerted upon the bottom layer of brick, if the weight of the brick only is considered, is only 100 pounds per square inch. From these facts it will readily be seen that the crushing strength of brick is not likely to be overtaxed in construction work. The crushing strength of brick is tested in machines specially constructed for the test. In soft-burned brick the crushing strength may be as low as 40 pounds per square inch. In making the test, parallel edges of the half of a brick are ground smooth and the brick is then placed between the bearing plates of the machine. The load is increased gradually until the strength of the brick is reached when it falls into pieces with a loud report. Absorption. Brick are porous. That is, they contain spaces not occupied by clay particles. The degree of porosity is determined by the amount of water that the brick will absorb. The porosity of a brick may depend upon a number of factors. It may depend upon the character of the clay used. A coarse, sandy clay will produce a more porous brick than a more aluminous clay. It may depend upon the degree PROPERTIES OF BRICK. 135 of burning, as a soft-burned brick will absorb more than a hard- burned brick. It may also depend upon the process of molding. Soft-mud brick, as a rule, are more porous than stiff -mud brick. The percentage of absorption in Iowa common brick ranges from 9.5 per cent to 22.7 per cent. One paving brick tested absorbed 4.7 per cent.* New Jersey soft-mud brick range from 5.36 per cent to 18.64 per cent, while stiff-mud brick range from 1.34 per cent to 14.29 per cent.f The following tests were made upon some bricks from this State. The samples tested, after being carefully dried, were weighed and then immersed in water for 48 hours. Upon being taken from the water, the moisture adhering to their surfaces was removed and they were re weighed. The difference between the weight of the dry brick and the wet brick gave the amount of water absorbed. By dividing this difference by the weight of the dry brick the percentage of absorption was determined. TABLE 25. ABSORPTION TESTS OF MISSISSIPPI BRICKS. Per cent of Locality Color Make of brick absorption Stonington Red Pressed 10.52 Yazoo City “ “ 15.00 “ “ “ “ 15.00 " “ “ “ 15.00 Oxford “ “ 14.09 “ “ “ 12.50 “ “ “ 12.76 “ “ “ 13.04 «« «• . 15.00 Starkville Red . 22.22 . 10.52 Chocolate .. . 5.00 “ “ . 5.26 Stiff mild 8.10 Red 5.26 Columbus Chocolate ..... . .. . 21.21 Red .. . 15.74 Amory Chocolate , - , .. . 15.00 Red .< 9.75 Maben .. 8.80 Red .. . 16.86 « .. . 26.86 It is thus seen that the percentage of absorption in dry-pressed brick ranges from 10.52 to 15 per cent. The percentage of absorption ♦See Vol. XIV, Iowa Geol. Sur., p. 695. tSee Vol. VI, N. J. Geol. Sur., pp. 254-5. 136 CLAYS OF MISSISSIPPI. in repressed brick ranges from 5 to 22.22 per cent. The percentage of absorption in stiff-mud brick ranges from 5.26 to 26.82 per cent. In the manufacture of these brick different kinds of clay were used and the degree of burning varied. All of those exhibiting a high per- centage of absorption were so ft -burned. Impact Strength Rattler Test . — Brick for the rattler impact test are placed in a polygonal cast-iron barrel which is made to revolve on trunnions. The length of the barrel is 20 inches and its diameter is 28 inches. It is a regular polygon of 14 sides. The brick are placed in the barrel together with a charge of cast-iron blocks. The barrel is then moved at a certain speed for a definite number of hours. The strength of the brick is then estimated by the amount of loss it has sustained due to abrasion. The charge consists of 12 brick and 300 pounds of iron blocks of two sizes. First, cubes of H inches in diameter having a collective weight of 225 pounds; second, blocks 2\ inches square and 4 J inches long with rounded edges and a collective weight of 75 pounds. The number of revolutions required for the test is 1,800 at the rate of 80 per minute. The brick must be perfectly dry. The loss is com- puted as per cent of the dry brick and the average of two tests taken The rules for this test, adopted by the National Brick Manu facturers’ Association, are as follows: “The standard rattler shall be 28 inches in diameter and 20 inches in length, inside measurements. Other dimensions may be employed between 26 and 30 inches diameter and 18 to 24 inches length, in which case the dimensions should be stated in reporting the test. Longer rattlers may be employed by the insertion of a diaphragm. “The barrel should be supported on trunnions at the ends with no shaft running through the rattling-chamber. The cross section should be a regular polgyon of 14 sides. The heads shall be of gray cast iron, not chilled or case-hardened. The staves shall preferably be composed of steel plates, as cast iron peens and ultimately breaks from the wearing action on the inner side. There shall be a space of one-fourth an inch between the staves for the escape of dust and small pieces. Machines having from 12 to 16 staves may be employed, with openings from J to f inch, but these variations from the standard should be mentioned in an official report. PROPERTIES OP BRICK. 137 “The charge shall consist of but one kind of brick at a time, nine paving blocks or twelve bricks being inserted, together with 300 pounds of cast-iron blocks. These shall be of two sizes, 75 pounds being of the larger and 225 pounds of the smaller size. The larger size shall be about 2£ inches square and 4£ inches long, with slightly rounded edges. All blocks shall be replaced by new ones when they have lost 10 per cent of their original weight. “The number of revolutions shall be 1,800 for a standard test at a speed between 28 and 30 per minute. “The bricks shall be thoroughly dried before testing. The loss shall be calculated as per cent of the weight of the dry bricks com- posing the charge, and no result shall be considered as official unless it is the average of two distinct and complete tests made on separate charges of brick.” (Materials of Construction, Johnson, p. 461a.) Tensile Strength. The tensile strength of ordinary brick varies from 40 to 400 pounds per square inch. The test is made by placing the specimen in the jaws of a machine and measuring the amount of pull necessary to break the section. The tensile strength of a large number of Mississippi brick clays was tested in both the raw and the burned state. These results are recorded under the discussion of the individual clays. No tests have been made upon the manufactured product of the various plants. The tensile strength of some of the burned clays ranges as high as 800 pounds per square inch. Transverse Strength. The transverse strength of a brick is measured by the load it will sustain when unequally supported. F or example , suppose a brick to be supported at each end and a load applied to a point midway between the supports. When the load added reaches the transverse strength of the brick the brick will be broken crosswise. The modulus of rupture is calculated by the use of a formula in which R = Modulus of rupture. W = Pressure of load. 1 = Distance between supports, b = Breadth of brick. h = Thickness of brick. _ _ j "D 3W1 and K = 2 bP 138 CLAYS OP MISSISSIPPI. Now, if a weight of 3,000 pounds be applied to a brick 4 inches wide and 2 inches thick, where the distance between the supports is 4 inches, its transverse strength will be as follows: 1,125 pounds. Weight of Brick. Common brick, having a size of 8J x 4 x 2 inches, have an average weight of 4J pounds. One thousand of such brick have a weight of 4,500 pounds or 2.01 long tons. Pressed brick of standard size have an average weight of 5 pounds and weigh 2.23 tons per 1,000. The average weight of 10 Mississippi pressed brick is 5.6 pounds. The average weight of 10 repressed brick of stiff-mud make is 4.7 pounds. The average weight of 10 stiff-mud brick is 4.6 pounds. These brick represent different kinds of clays and different sizes of molds. Size of Brick. The size of a standard brick is 8J inches long by 4 inches wide by 2 inches thick. A brick of this size contains 66 cubic inches. It requires 26.2 bricks of standard size to make 1 cubic foot and 707 standard brick to make 1 cubic yard. The following table exhibits the sizes of some Mississippi brick. These brick vary in volume from 64 cubic inches to 95 cubic inches. One, alone, falls below the volume of a standard brick, and that one by 2 cubic inches only. SIZE OF SOME MISSISSIPPI BRICK. PROPERTIES OF BRICK. 139 8 Or- 6 - - a . a ci O - • .JsM® , JN . Jcq . . Icq . . . |M Hn “VirnH Ih Ho H« H H» Hh -W *>-< o o o -P o O T P • • cj • n r TV ^ »d *d h g o ^ o .2? ’_5 h w D O "O o 'O O O O CT O r« Or; C ^ aj O 2 ) ■ 70.81 79.23 80.03 66.85 71.03 44.23 42.92 Iron oxide (Fe 2 C> 3 ) . . . . 11.20 .67 1.68 3.77 .56 .81 .61 Aluminum oxideCALOs)!! .20 13.91 12.00 20.54 20.29 38.82 41.30 Calcium oxide (CaO) . . .60 .59 .26 .21 .20 .19 .37 Magnesium oxide(MgO) .50 .21 .00 .18 .13 .13 .13 Sulphur trioxide(S 03 ) . trace trace trace trace .25 .45 .18 Total 100.09 99.97 99.27 100.14 99.98 100.12 100.57 Clay No. 1 is from the public road near the fish pond at luka. No. 2 is from the public road 2 miles south of Old Eastport. No. 3 is from the R. W. Peden farm, and No. 4 is from the Jas. Turner farm. Nos. 5, 6 and 7 were collected by Dr. F. T. Carmack from near Tisho- mingo city. Eutaw (Tombigbee ). — The Eutaw formation consists of greenish colored sands containing, in some localities, indurated layers of irregularly bedded sandstones, and in other places thin laminae of clay. The sands are micaceous and contain some calcareous matter which increases in amount toward the upper horizon where it passes by a gradual transition into the overlying Selma chalk. The upper beds are abundantly fossiliferous. The lower beds are less fossiliferous and contain irregular masses of indurated materials and lenticular bodies of iron sulphide. Lignite and lignitic clays are not of infrequent occurrence in the lower beds. Typical exposures of the fossiliferous strata are to be found along the bluffs of the Tombigbee River from Amory to Columbus. The river, sinking its channel into the soft rocks of the Eutaw, traces the western boundary of the formation across the northeastern part of the State. The Eutaw forms the chief water-bearing stratum for the northeastern prairie belt, and its collecting ground is along the Tom- bigbee River basin. 158 CLAYS OF MISSISSIPPI. Selma Chalk ( rotten limestone ). — The rock of the Selma chalk is for the most part a fine-grained cretaceous limestone. On unweathered surfaces it has a bluish tint ; on weathered areas it is white in color. Thin layers of crinoidal limestone and lenticular sandstone masses are occasionally encountered. Thin seams of asphaltum and nodular forms of iron pyrites occur in some outcrops. The amount of calcium carbonate in the formation varies, but in general it increases toward the southern portion of the area. The thickness also increases toward the south, being about 75 feet at the northern line of the State and reaching a thickness of about 1,000 feet near its southern limit. The transition from the underlying arenaceous Eutaw to the highly calcareous Selma is gradual, so that the lowermost bed of the latter contains a large percentage of sand and a correspondingly small amount of calcium carbonate. Both vertically and horizontally the chalk varies in the amount of clay which it contains. In some places the formation contains as much as 16 per cent of alumina. The white rock, the weathered product of the blue, naturally contains more clay than the unweathered rock, since some of the calcium carbonate has been removed during the process of weathering and the insoluble aluminum silicate left behind. TABLE 34. ANALYSES OF SELMA CHALK. No. 1 Moisture (H 2 O) 1.10 Volatile matter (CO 2 ) 34.20 Silicon dioxide (SiOj) 18.70 Iron oxide (Fe20s) 6.00 Aluminum oxide (AI 2 O 3 ) .00 Calcium oxide (CaO) 45.62 Magnesium oxide (MgO) 1.72 Sulphur trioxide (SO3) 1.11 Total 98.45 No. 2 No. 3 No. 4 No. 5 No. 6 .94 1.08 .40 1.50 2.75 42.05 27.10 25.60 24.50 22.61 9.84 14.84 25.27 29.98 32.81 2.58 4.50 10.35 5.60 4.65 .19 15.59 4.81 5.45 11.15 38.65 32.89 32.85 31.62 22.69 .18 .41 .84 .14 1.53 2.05 3.30 .32 .21 1.55 96.48 99.71 100.64 99.02 99.74 Sample No. 1 is from Okolona, Chickasaw County; Nos. 2, 4 and 5 are from Oktibbeha County; No. 3 is from Tupelo, Lee County, and No. 6 is from West Point, Clay County. The majority of these samples contain clay, the per cent ranging from .48 to 39.44. They also con- tain some sand. The greater number of these samples were taken from the surface of the limestone where weathering processes have caused a considerable loss of calcium carbonate. Some unweathered GEOLOGY OF MISSISSIPPI CLAYS. 159 specimens of chalk have exhibited more than 90 per cent of lime- The weathering of the limestone has produced the main supply of brick clay of the Selma area. Ripley . — Overlying the Selma chalk and bordering the north- western portion of its outcrop are the marls of the Ripley. In some places the chief component of the marl is clay. They are generally highly fossiliferous and greenish in color, due to the presence of glau- conite. In some exposures there are thinly bedded arenaceous lime- stones. The composition of one of these arenaceous rocks from Tippah County is given below. TABLE 35. ANALYSIS OF RIPLEY SANDSTONE. Moisture (H 2 O) 3.94 Volatile matter (CO 2 ) 1.82 Silicon dioxide (Si 02 ) 82.95 Iron oxide (Fe 203 ) 6.50 Aluminum oxide ( AI 2 O 3 ) .87 Calcium oxide (CaO) 2.00 Magnesium oxide (MgO) .54 Sulphur trioxide (SO 3 ) .60 Total 99.22 Near the old mill in the northern part of the town of Ripley the following section is exposed: Section of Ripley in the Town of Ripley. Feet 4. Yellow to brown loam 4 3. Gray clay 3 2. White shally rock 2 1. Fossiliferous green sand 10 The gray clay from No. 3 has the chemical composition recorded in the following analysis: TABLE 36. ANALYSIS OF CLAY, RIPLEY. Moisture (H 2 O) 8.23 Volatile matter (CO 2 etc.) 3.96 Silicon dioxide (Si 02 ) 67.10 Iron oxide (Fe 20 s) 6.60 Aluminum oxide (AI 2 O 3 ) 10.96 Calcium oxide (CaO) 1.87 Magnesium oxide (MgO) .54 Sulphur trioxide (SO 3 ) .51 Total 99.77 160 CLAYS OF MISSISSIPPI. CENOZOIC. TERTIARY. Eocene. The eocene of Mississippi is composed of the following stages: Midway, Wilcox, Claiborne and Jackson. Midway . — The Midway is composed of two formations, the Clayton limestones and the Porter’s Creek (Flatwoods) clays. The latter are gray laminated and somewhat shaly clays. Some of the lowermost beds contain small white concretions of irregular shape and usually of small size. In the upper beds, layers of ironstone concretions abound. These are usually lens-shaped masses; some are irregular in form. Occasionally the lens-like masses form a continuous layer which per- sists for several rods. The clay is frequently micaceous. It is exceed- ingly fine-grained and highly silicious, containing as much as 70 per cent of silicon dioxide. The Flatwoods clay is exceedingly sticky and the wagon roads across its outcrop are kept in condition wi-th great difficulty. Though of highly silicious character, the grains of silica are exceedingly small so that they are not detected by ordinary methods of observation. The following table shows the analyses of some samples of the Flatwoods clays: TABLE 37. ANALYSES OF FLATWOOD CLAYS. No. 1 No. 2 No. 3 No. 4 Moisture (H 2 O) 2.97 4.50 5.65 4.95 Volatile matter (CO 2 etc.) 3.91 7.77 5.04 9.05 Silicon dioxide (SiC> 2 ) 75.60 61.62 71.47 65.60 Iron oxide (Fe20j) .... . 8.24 15.29 6.97 7.20 Aluminum oxide (AI 2 O 8 ) 7.00 .87 9.45 10.50 Calcium oxide (CaO) 1.20 .81 .40 1.12 Magnesium oxide (MgO) 67 .69 .63 .60 Total 99.83 99.74 99.98 Clays Nos. 1 and 4 are from Oktibbeha County; No. 2 is from Winston County, and No. 3 is from Noxubee County. Wilcox {Lagrange ). — The Wilcox formation consists of sands and clays with intercalated beds of lignite. The sands are for the most part unconsolidated sediments, though occasionally irregular masses of sandstone or ironstone appear in the outcrops of its strata. The GEOLOGY OF MISSISSIPPI CLAYS. 161 sands are very much cross-bedded and inter-bedded with thin seams of clay. The colors are variegated. In many places, thick beds of pink or white pottery clays are present. In the upper portion of the formation there are beds of shale-like clay of a dark color. The clays have a low specific gravity and are fine in grain. There is an outcrop of these clays in the bank of the Yalobusha River, at Grenada. The bed has a thickness of about 40 feet. The chemical composition of a sample of the clay is given below: TABLE 38. ANALYSIS OF WILCOX CLAY. GRENADA. Moisture (H 2 O) 5.91 Volatile matter (CO 2 ) 8.75 Silicon dioxide (Si 02 ) 61.80 Iron oxide (Fe 20 s) 3.88 Aluminum oxide (AI2O3) 16.50 Calcium oxide (CaO) 1.00 Magnesium oxide (MgO) .23 Sulphur trioxide (SO 3 ) .19 Total 98.26 The pink and the white clays of the lower and middle horizons of the Wilcox are used in a number of counties in the manufacture of stoneware. The following table gives the analyses of some of the pottery clays: TABLE 39. ANALYSES OF WILCOX POTTERY CLAYS. No. 1 Moisture (H 2 O) 66 Volatile matter (CO 2 etc.) 7.25 Silicon dioxide (Si 02 ) 62.41 Iron oxide (Fe 203 ) 2.80 Aluminum oxide (AI 2 O 3 ) 24.02 Calcium oxide (CaO) 57 Magnesium oxide (MgO) 50 Sulphur trioxide (SO 3 ) 56 Total 98.97 No. 2 No. 3 No. 4 No. 5 No. 6 1.84 1.92 .62 .23 1.47 8.23 7.66 7.02 4.81 9.24 60.78 63.56 64.86 75.78 59.82 3.52 2.83 4.19 3.56 1.26 24.12 21.92 20.70 14.11 27.19 .73 .48 .69 .54 .49 .38 .62 .59 .52 .37 .38 .28 trace .00 .31 99.98 99.29 98.67 99.55 100.16 Clays Nos. 1, 2 and 3 are from Marshall County; Nos. 4 and 5 are from Lafayette County; No. 6 is from Webster County. Claiborne . — The rocks of the Claiborne are divided into Tallahatta buhrstone (Siliceous Claiborne), Lisbon, and the undifferentiated Claiborne. 5 162 CLAYS OF MISSISSIPPI. The Tallahatta buhrstone is composed of hard white quartz rocks with impure calcareous sandstones and claystones. In some localities the formation consists of ferruginous sands, but slightly cemented and containing numerous fossils. In other localities the sandstones are cherty in character, with thin layers inter-bedded with sandy clays. The white quartz rock constitutes one of our best road metals. Unfortunately very little of it has been used in this State. During 1906, 100 carloads were shipped from West to Louisiana to be used in street pavement work. The Lisbon is composed of white sands containing calcareous material, greenish marls, and lignitic clays. The calcareous beds are highly fossiliferous. Species of the genera Ostrea and Pecten are the most abundant fossils. Between the Lisbon beds and the Jackson formation is a great thickness of undifferentiated Claiborne. Jackson . — The Jackson formation is composed of clays, marls and sands. The clays in some outcrops contain the bones of Zeuglodon, an extinct marine animal of huge size. Aggregates of selenite crystals are abundant in some layers. The marls are very generally fossil- iferous. The sands are sometimes interbedded with lignitic clays or lignite. The outcrop of the Jackson and the Vicksburg forms the central prairie belt of the State. At Morton, there is an exposure of the upper Jackson beds which has the following stratigraphy: Section of Upper Jackson Beds at Morton. Feet 5. Grayish clay in thin layers 5 4. Lignite and lignitic clay 6 3. White sand with clay partings 15 And at a lower level : Feel 2. Layers of yellow sand and gray clay 20 1. Gray clay 6 On the south side of the ridge where the above-mentioned exposure occurs, the following section is exposed: 3. Orange sand with gravel and ironstone (Lafayette). 2. Clay with purple clay stones (Grand Gulf?). 1. Gray laminated clay with selenite crystals (Jackson). GEOLOGY OF MISSISSIPPI CLAYS. 163 At Barnett, a yellow laminated clay streaked with blue, has a thickness of at least 25 feet. The clay contains crystals of selenite and fossils. It has the following chemical properties: TABLE 40. ANALYSIS OF BARNETT CLAY. Moisture (H 2 O) Volatile matter (CO 2 etc.) Silicon dioxide (Si 02 ) Aluminum oxide (AI2O3) . Iron oxide (Fe 20 $) Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SO 3 ) 5.55 13.80 38.75 22.83 3.14 14.25 1.01 trace Total 99.33 Oligocene. Vicksburg . — The line of outcrop of the Vicksburg parallels the Jackson on the South. Its rocks are limestones and marls. Typical exposures occur in the bluffs of the river at Vicksburg. In the exposures along the river front, there are five or six layers of limestone interbedded with marl and clay. They overlie dark colored clays and sands. The limestone varies in thickness in the different ledges and even in the same ledge. The individual layers are from 1 to 6 feet thick. The following table gives the chemical composition of Vicksburg limestone from a number of exposures: TABLE 41. ANALYSES OF VICKSBURG LIMESTONE. No. 1 No. 2 No 3 No. 4 Moisture (H 2 O) 40 1.00 1.79 2.10 Volatile matter (CO2 etc.) 37.22 35.20 35.40 33.16 Silicon dioxide (Si 02 ) 7.08 7.31 6.77 14.88 Iron oxide (Fe 20 s) 2.50 4.00 2.00 3.59 Aluminum oxide (AI2O3) 61 13.66 4.68 5.70 Calcium oxide (CaO) 50.44 36.62 45.51 36.86 Magnesium oxide (MgO) 1.07 .29 .64 .99 Sulphur trioxide (SO 3 ) 38 2.78 3.00 .24 Total 99.70 100.86 99.79 97.72 Sample No. 1 is from Warren County; No. 2 and No. 3 are from Wayne County, and No. 4 is from Rankin County. At Brandon, in Rankin County, there are some excellent exposures of Vicksburg limestone. On the Robinson place, 4 miles southeast 164 CLAYS OF MISSISSIPPI. of Brandon, there is a stone quarry in which six layers of limestone are found interbedded with marl in the following stratigraphic order: Section of Vicksburg at Robinson Quarry , near Brandon. Feet 13. Soil and decomposed rock 2 12. Limestone 1-1 i 11. Marl 1 10. Limestone 2 9. Marl 2 8. Limestone 11 7. Marl 11 6. Limestone 11-2 5. Marl 2 4. Limestone 2 3. Marl 1} 2. Limestone 2 1. Marl 2 The limestone is bluish on fresh fractures but weathers white. It is fossiliferous, containing abundant evidence of marine life. Miocene. Grand Gulf . — In Mississippi, the Grand Gulf formation is made up of gray, clayey sandstones, white quartz rocks and clays. The latter contain considerable organic matter and are of a dark color in many areas. The Pascagoula is thought by some to be a part of the Grand Gulf. Samples of silicious claystones of the Grand Gulf have been analyzed with the following results: TABLE 42. ANALYSES OF GRAND GULF CLAYSTONES. Per cent No. 1 No. 2 No. 3 No. 4 Moisture (H 2 O) 3.59 .74 .75 • .50 Volatile matter (CO 2 etc.) ..... 2.93 1.51 3.50 .38 Silicon dioxide (Si 02 ) 77.44 92.13 81.85 88.11 Iron oxide (Fe 2 03 ) 4.17 1.61 3.00 4.00 Aluminum oxide (AI 2 O 3 ) 11.09 2.96 8.32 5.81 Calcium oxide (CaO) 53 .54 .82 .56 Magnesium oxide (MgO) 31 .42 .00 .00 Sulphur trioxide (SO 3 ) 05 .05 2.84 1.50 Total 100.11 99.96 101.08 100.86 Some beds of the Grand Gulf formation are composed of clear quartz grains cemented together with a silicious cement so that they present the appearance and hardness of quartzites. White chalk-like clays occur in some localities. Plate XXIII. B. SOFT-MUD BRICK HACKED UNDERED COVER SHED. GEOLOGY OF MISSISSIPPI CLAYS. 165 The table given below contains the analyses of some of the Grand Gulf clays: TABLE 43. ANALYSES OF GRAND GULF CLAYS. No. 1 No. 2 No. 3 No. 4 Moisture (H2O) 60 2.36 3.65 1.09 Volatile matter (CO2 etc.) 5.10 4.01 1.16 2.98 Silicon dioxide (SiC>2) 72.32 74.92 68.28 82.42 Iron oxide (Fe 2 C> 3 ) 3.00 2.96 10.00 2.40 Aluminum oxide (AI2O3) 15.81 13.25 1.76 9.65 Calcium oxide (CaO) 47 .20 .87 .70 Magnesium oxide (MgO) .38 .76 .46 Sulphur trioxide (SO3) 2.75 2.12 4.26 .12 Total 100.05 100.20 90.14 99.62 Nos. 1, 2 and 4 are from Jefferson County and No. 3 is from Warren County. QUATERNARY. Lafayette . — The rocks of the Lafayette consist of sands, gravels, conglomerates, ironstones, loams and plastic clays. It is one of the most widely distributed formations in the State occupying practically all of the surface of the higher lands. Bright coloring is characteristic of nearly every outcrop. Orange, purple, pink, yellow, buff and white colored sands and clays occur in a great diversity of stratigraphic relationships. Blotched and mottled surfaces abruptly changing from one color to another are common. The prevailing coloration is largely due to the presence of ferric iron. The thickness of the formation rarely exceeds 50 feet. The strati- graphic appearance of many of the sands is so suggestive of dune deposition that the conclusion that they are of eolian origin would seem irresistible but for the presence of “pebble” clay. The shape, mass, and distribution of this is not in harmony with such a view. Three modes of origin have been suggested for the Lafayette. First, the glacio -fluvial hypothesis suggested by Hilgard in a Report on the Agriculture and Geology of Mississippi, published in 1860. Second, the marine deposition hypothesis, published by McGee in Twelfth Annual Report of the United States Geological Survey. Third, the Aggradation hypothesis, suggested by Chamberlin and Salisbury in Earth History, Vol. Ill, pp. 305-307. The statement of the last hypothesis is given in the words of the authors: “As here interpreted, the Lafayette formation belongs to an important class, 166 CLAYS OF MISSISSIPPI. long neglected, but now coming into recognition, whose distinctive features are less critically familiar than those of marine, lacustrine, and typical fluvatile formations. The preferred interpretation is as follows: After the Cretaceous base-leveling of the region, the Appa- lachian tract was bowed up and a new stage of degradation inaugurated. During the long Eccene period, a partial peneplaining of the less resistant tracts was accomplished. This was slightly interrupted by the Oligiocene deformation, and the streams mildly rejuvenated in the more responsive tracts. During the Miocene period, base-leveling was resumed, abetted by relative subsidence along shore, as indicated by the landward spread of the Miocene sea, and the open low grade valleys and abundant low cols of the region west of the Appalachians, if the interpretation here given be correct. At the opening of the Pliocene, therefore, the Appalachian tract is supposed to have been affected by broad, flat, intermontane valleys, mantled by a deep layer of residual decomposition products. The 'Piedmcnt tract skirting the Appalachians is supposed to have been flanked on the seaward side by a peneplain near sea level, and on the other side by broad, open valleys of low gradient. It is assumed that the upward bowing was felt first in a relatively narrow belt along the predetermined axis, that the rise was gradual, and that the rising arch increased its breadth as it rose. The first bowing along the axis rejuvenated the head waters of the streams which reached it, and the surface, deeply mantled with residuum accumulated during the peneplaining stage, readily furnished load to the streams in flood stages. When the streams reached that portion of the peneplain not yet affected by the bowing, they found themselves loaded beyond their competency, and gave up part of their load. Thus arose a zone of deposition along the bowed tract, with continued rise, the mountain ward border of the depositional zone is supposed to have been shifted seaward, and the previous border elevated and subjected to erosion, while the material removed was re-deposited in a new zone farther from the axis of rise. “Thus the process is presumed to have continued till the border of the lifted tract passed beyond the present seacoast, after which the whole mantle was subjected to erosion, which has reached a notable degree of advancement before the first known glacio -fluvial deposits were laid down.” Plate XXIV. SODDING LOESS SLOPES WITH BERMUDA GRASS AS A PROTECTION AGAINST EROSION, NATIONAL PARK, VICKSBURG. GEOLOGY OF MISSISSIPPI CLAYS. 167 Natchez . — The Natchez formation has its typical development at Natchez, where the thickness assigned is 200 feet. It rests erosively unconformable upon the Lafayette. The formation is composed of sands and gravels containing calcareous clays. According to Cham- berlin, its age is either sub-Aftonian or Aftonian. (See Earth History, Vol. Ill, pp. 386-8.) Loess ( Bluff Formation). — A fine- silty material of brownish color containing concretions and tubules of lime carbonate and shells of species of gastropods is called the Loess. In thickness, it varies from a few feet to a hundred or more. The Loess is thought to be a deposit formed largely by winds, which transported silt and rock flour from the flood plains of rivers and from over-washed plains during glacial or inter-glacial epochs. In Mississippi the Loess occupies a tract along the eastern border of the Mississippi Valley. The tract is narrow and the thickest part of the deposit is upon the immediate banks of the valley and thins rapidly toward the east. In the majority of places the upper surface is occupied by a bed of residual clay, having a thickness of 6 to 10 feet, and much used for brick clay. Columbia . — The brown and yellow loams which occupy the surface of practically all the hill country of the State have been assigned to the Columbia. In point of time these loams represent in some instances doubtless all of the time which has elapsed since the Lafayette depo- sition. In other instances only that time which has elapsed since the deposition of the Loess. The time which has elapsed since the deposition of the Lafayette has permitted the accumulation of various surficial deposits of clay, sand and loam. These have resulted in a large measure from the disintegration and decomposition of older formations. That the formation is largely residual is not to be denied. That it is composed partly of transported material is within the bounds of reasonable probability. That such transported material is largely of Eolian origin is also very probable. The brown loam and clay which rest upon the Loess is without doubt a residual product of the latter’s decomposition. It is probable that the loams are for the most part only modified forms of the Loess. The Loess thins out and loses its identity a short distance from the 168 CLAYS OF MISSISSIPPI. Mississippi bluffs. The loams, however, cover the whole State except where they have been removed by erosion. Recent Deposits . — The recent deposits consist of undifferentiated loams of the hill country, the alluvial deposits of the flood plains, and recent deposits along the coast, some of which are marine, others lacustrine and others estuarine. The largest area of recent deposits is that of the Yazoo basin. This basin is a flood plain area between the Yazoo River and the Mississippi River. The rocks, sands, clays and silts have been deposited by the streams. The flood plain material is of two kinds. First, the sandy loam which is found along the courses of the streams. Following the law of deposition, when a stream carrying sediment overflows its banks the water begins to lose its velocity and to deposit the coarser, heavier particles of its suspended matter near the streams. Second, the finer clayey materials which are found on the inter-stream areas. According to the same law of deposition, the finer particles are carried .longer in suspension and are dropped farther from the main channel. Fre- quently coarse sediments are carried into the inter-stream areas by temporary currents set up during overflows. Therefore, layers of sandy loam are often interbedded with layers of plastic clay. CHAPTER IX. THE CLAYS AND CLAY INDUSTRIES OF NORTHERN MISSISSIPPI BY COUNTIES. The following chapter contains a statement of our present knowl- edge of the clays and clay industries of the northern half of the State. The report is not complete and is only preliminary. The clay in- dustries, like all other industries in the State, are developing so rapidly that the collector of statistics scarcely turns his back upon a field before new plants have sprung into existence. The following is a list of the counties wholly or partly included in the report: Alcorn Holmes Monroe Tate Attala Kemper Newton Tippah Carroll Lafayette Noxubee Tunica Clay Lauderdale Oktibbeha Union Chickasaw Lee Panola Warren Choctaw Leflore Pontotoc Washington Coahoma Lowndes Prentiss Webster De Soto Madison Rankin Winston Grenada Marshall Scott Yalobusha Hinds Montgomery Sunflower Yazoo ALCORN COUNTY. GEOLOGY. The bed-rock of this county is formed of Cretaceous strata. The extreme southeastern corner of the county is underlain by the Tusca- loosa sands and clays. The eastern part of the county is underlain by the sands of the Eutaw (Tombigbee) group. The central portion of the county has for its subformation the Selma chalk, and the western portion is occupied by the Ripley. The principal mantle rock formations are the Lafayette sands and clays and the Columbia loams. There are also some residual deposits formed directly from the bed- 170 CLAYS OF MISSISSIPPI. rock formations. The Lafayette formation is represented by isolated outcrops. • The Columbia loam has a wider distribution. In the Selma chalk area the soil often rests directly upon the chalk. CLAY INDUSTRY. Corinth . — The residual clay from the Selma is utilized in the county in the manufacture of brick. Lafayette sandy clay and the Columbia loams are used with the residual Selma, since the latter is generally too plastic. At Corinth, the residual clay of the Selma chalk and the Lafayette clay are used in the manufacture of brick by the Corinth Brick Manufacturing Co. In the pit the following stratigraphic al conditions arc revealed: Section of the Pit of the Corinth Brick Mfg. Co ., Corinth. Feet 4. Yellowish loam (Columbia) 3 3. Red sandy clay (Lafayette) 4 2. Plastic clay (residual Selma) 2-3 1. White chalk (Selma) In the manufacture of brick a mixture of Nos. 2, 3 and 4 is used. The clay is prepared in a granulator and tempered in a pug mill. It is molded in a stiff -mud, end-cut machine. The brick are burned in rectangular, up-draft kilns of the clamp type. A sample of clay taken from layer No. 2, upon analysis, gave the following results: TABLE 44. ANALYSIS OF RESIDUAL SELMA CLAY, CORINTH. No. 104 Moisture (H 2 0) 3.85 Volatile matter (C0 2 ) 4.45 Silicon dioxide (Si0 2 ) 76.77 Iron oxide (Fe 2 03 ) 6.25 Aluminum oxide (AI 2 O 3 ) 8.56 Calcium oxide (CaO) .31 Magnesium oxide (MgO) .04 Sulphur trioxide (SO 3 ) .00 Total 100.23 RATIONAL ANALYSIS. , Clay substance 21.65 Free silica 66.72 Impurities 6.60 A sample of the Selma chalk collected from this locality by A. F. Crider has the following chemical composition: Plate XXV. OUTCROP OF BUHRSTONE SHALE-CLAY, VAIDEN. CLAYS OF NORTHERN MISSISSIPPI. 171 TABLE 45. ANALYSIS OF SELMA LIMESTONE, CORINTH. 4.47 23.70 25.40 6.88 8.62 26.37 .58 .64 Moisture (HjO) Volatile matter (CO2 etc.) Silicon dioxide (SiOj) Aluminum oxide (AI2O3) . . Iron oxide (Fe20s) Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SO3) . . . . Total 96.66 Clay from layer No. 2 of the above section contains 17.40 per cent of clay and some silica. It cannot be used alone in the manufacture of brick. The chief objections to its use are : (a) the large amount of soluble salts which it contains; ( b ) an excess of calcium carbonate; (c) high plasticity. The soluble salts are liable to produce kiln-white or wall-white, and calcium carbonate is liable to cause cracking . f the ware, and the high plasticity may prevent successful drying ex< .q t by extremely slow methods. A. sample of clay from layer No. 3 has the following physical properties: It requires 19 per cent of water to render it plastic. The tensile strength of its raw brickettes is 87 pounds per square inch; when burned it has a tensile strength of 150 pounds per square inch. The color of the burned brickettes is a deep red. The total shrinkage is only 2 per cent. The clay slakes very rapidly. This clay lacks sufficient plasticity for the stiff-mud process of molding. In con- nection with No. 4 it could be utilized in the manufacture of soft-mud brick. No. 4 is a loam which is lacking in plasticity. It doc ; not possess high enough bonding power to make good brick. A mixture of these three layers in the proper proportion is essential to a good stiff-mud product. To obtain the best results the clays should be crushed and thoroughly mixed before going to the molding machine. In case a large amount of clay from No. 2 is used, the brick ought to be carefully guarded from air currents for the first few hours after being taken from the machine. Rienzi . — In 1906, Mr. J. D. Furtick of Ricnzi was engaged in the manufacture of brick for local use. The brick were molded by the 172 CLAYS OF MISSISSIPPI. soft-mud. process and burned in rectangular, up-draft scove kilns. ; I'The pit from which the clay was taken has the following strati- graphy: Section of Clay Pit , Rienzi. 4. Soil 3. White “hard pan” fine sand 2. Yellowish clay (Columbia?). 1. Water bearing sand Feet 1 1 10 i Layer No. 2 is light gray in the upper portion and bluish in color in the lower portion. The grayish clay has a total shrinkage of 5 per cent. Its tensile strength in the raw state is 182 pounds. Hard- burned brickettes have a strength of 322 pounds. It requires 27 per cent of water to render it plastic. In passing from the stiff -mud to the burnt state it loses 33 per cent of its weight. The burned brick- ettes absorb 14.92 per cent of water. The white clay absorbs 26.66 per cent of water. A sample of No. 3 required 16 per cent of water to render it plastic. It has a total shrinkage of 2 per cent. In the raw state its tensile * strength is only 45 pounds per square inch, and when burned only 30 pounds per square inch. It is composed of very fine silica, and lacks bonding power. ATTALA COUNTY. GEOLOGY. Attala County lies partly within the Wilcox, but almost wholly within the Claiborne area. The surface formations are of Lafayette and Columbia age. CLAY INDUSTRY. Kosciusko . — The clay from the Columbia is used at Kosciusko in the manufacture of brick, in a plant operated by Storer and Miller. The plant was first established by A. M. Storer in 1902, and in 1906 the Storer and Miller Company was formed. The clay is tempered in a pug mill and molded in an end-cut stiff-mud machine. The kilns are up-draft clamp kilns of rectangular shape. The brick are dried on pallets in open covered racks. The second bottom clays of the surface formations are, generally speaking, the best clays for the manufacture of stiff-mud brick. The Lafayette and Columbia loams of the higher lands may be used in the manufacture of soft-mud brick. The aluminous clays of the Plate XXVI. B. EROSION IN THE LAFAYETTE, VAIDEN. CLAYS OF NORTHERN MISSISSIPPI. 173 Wilcox may be utilized in the manufacture of a light colored, dry- pressed brick. The white color can be varied by sprinkling the sur- face of the brick with iron or manganese to produce specks or spots in burning. These spotted brick make a very attractive ware. CARROLL COUNTY. GEOLOGY. The strata of the Tallahatta buhrstone constitute the bed-rock of Carroll County. The rocks consist of clays, sands and quartzites. The clays are exposed in cuts and along the banks of the streams; the quartzites form the cap-rock for some of the inter-stream areas. The mantle rock formations of the county are Lafayette, Loess, Columbia loam, and the alluvium of the Yazoo basin. In a railroad cut on the Illinois Central, south of the station at Vaiden, there are exposed about 30 feet of laminated clay belonging to the Claiborne. This clay is of a brownish-gray color, varying to purple and weather- ing to red or purple. The clay is interbedded with layers of very sandy white clay. It also contains thin wavy partings of limonite. In a small depression on the west side of the cut, a bad-land type of topography has been developed, and the following stratigraphic features are revealed: Section near Vaiden. » Feet 5. Soil 1 4. Brown loam 8 3. Reddish clay 10 2. Red and white mottled clay 10 1. Grayish clay 5 The reddish clay of No. 3 is probably Lafayette, though it has no gravel and is very similar to the residual clay of No. 1. The line of separation of No. 3 and No. 4 is more clearly marked by change in texture than by change in color. Wherever No. 4 has been com- pletely removed by erosion, the exposed surface of No. 3 cracks into blocks of circular shapes. This is due to the high plasticity and excessive shrinkage of the clay. In some places No. 3 contains small flat ironstone concretions. The clay from No. 1 requires 27 per cent of water for plasticity. It has a total shrinkage of 15 per cent. The raw clay brickettes 174 CLAYS OF MISSISSIPPI. have a tensile strength of 187 pounds per square inch. When burned, the tensile strength is 200 pounds per square inch. Absorption is 14.63 per cent. The chemical composition of a sample of No. 1 is given below as analysis No. 83: TABLE 46. ANALYSIS OF RESIDUAL CLAY. VAIDEN. No. 83 Moisture (H*0) 10.06 Volatile matter (COj etc.) 7.00 Silicon dioxide (SiOj) 59.22 Iron oxide (FejOj) 4.70 Aluminum oxide (AljOj) 10.30 Calcium oxide (CaO) 1.68 Magnesium oxide (MgO) 1.18 Sulphur trioxide (SOj) .23 Total 94.37 RATIONAL ANALYSIS. Clay substance 26.06 Free silica 15.76 Impurities 7.89 The red residual clay, No. 2, of the section given above, has the following composition: TABLE 47. ANALYSIS OF RESIDUAL CLAY, VAIDEN. No. 84 Moisture (H 2 O) 6.77 Volatile matter (CO 2 etc.) 6.75 Silicon dioxide (Si02) 66.06 Iron oxide (Fe20j) 6.25 Aluminum oxide (A^Oj) 9.47 Calcium oxide (CaO) 1.95 Magnesium oxide (MgO) .72 Sulphur trioxide (SO 3 ) .10 Total.... 97.87 RATIONAL ANALYSIS. Clay substance 23.96 Free silica 51.58 Impurities 9.02 This clay has too high a shrinkage to be utilized without the aid of non-plastic material. It would also require thorough crushing before it could be used, as it slakes slowly. The non-plastic material of the Lafayette or Columbia near at hand could be used to dilute it. Plate XXVII. UP-DRAFT CLAMP KILNS, END VIEW, WEST POINT, CLAYS OF NORTHERN MISSISSIPPI. 175 CLAY COUNTY* GEOLOGY. The bed-rock of Clay County belongs to the Cretaceous and the Eocene periods. The eastern part of the county is underlain by the Eutaw (Tombigbee) formation; the central portion by the Selma chalk, and the western part by the Porter’s Creek (Flatwoods). The mantle rock formations are the Lafayette and the Columbia. The Lafayette occurs only in isolated areas. The Columbia has a much larger distribution, but there are areas in which the soil rests directly upon the surface of the Selma without intervening mantle rock. Much of the surface clay has been formed by the decom- position of the Selma chalk. CLAY INDUSTRY. West Point . — In the pit belonging to the West Point Manufacturing Company, at West Point, the clay rests upon a stratum of the Selma chalk. On weathered surfaces the chalk is white, but un weathered surfaces are blue. The chalk at this point is very fossiliferous, con- taining many specimens of the genus Inoceramus. The limestone immediately underlying the clay contains sufficient clay to render it plastic. When molded into brickettes it is white or blue, depending on whether the weathered or un weathered chalk is taken. The burned clay has a white or light yellow color. The brickettes have a tensile strength of 152 pounds per square inch in the un burned state. Its air shrinkage is about 6 per cent. Samples of this limestone and the overlying clay have the following composi- tion: TABLE 48. ANALYSES OF SELMA LIMESTONE AND RESIDUAL CLAY, WEST POINT. No. 32 No. 33 4.25 2.75 7.77 22.61 73.70 32.81 11.14 4.65 3.81 11.15 1.04 22.69 .00 1.53 .21 1.55 Total No. 32. Residual clay. No. 33. Selma limestone 99.97 99.74 Moisture (H 2 O) Volatile matter (CO 2 etc.) Silicon dioxide (Si 02 ) Iron oxide (Fe 20 s) Aluminum oxide (AI 2 O 3 ) . Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SO 3 ) 176 CLAYS OF MISSISSIPPI. The above mentioned limestone contains 28.20 per cent of clay and a small per cent of free silica. Doubtless the low percentage of calcium carbonate is due to the solvent action of circulating waters which dissolved out and carried away much of this soluble constituent and produced a concentration of such insolubles as clay and silica. As the distance from the limestone to the top of the clay deposit increases, there is a corresponding decrease in the amount of calcium carbonate. On the other hand, the amount of silica increases to the top while the amount of alumina increases to a certain point, and then decreases as the amount of free silica increases. The clay immediately overlying the limestone contains a high per cent of calcium carbonate in some places. In burning, the calcium compound is calcined and when the bricks absorb moisture the lime slakes and produces heat. The heat and the swelling of the lime cause the brick to crack open. This would not occur if the lime was thor- oughly mixed throughout the clay in small particles. The clay con- tains soluble salts, which produce efflorescence on the brick in drying. The principal salt is calcium sulphate, formed by the decomposition of pyrite in the presence of calcium carbonate. This salt is brought to the surface by the water which comes from the brick during drying, and forms a white coating on the surface. The bottom clay is so plastic that it gives trouble in drying when used alone. The best results are to be obtained by not taking the clay too close to the limestone; and by mixing the lower clay with the clay from the more non-plastic layer. Other non-plastic materials, such as sand and cinders, may be used to facilitate the drying of the clay; but by the use of the top clay the loss of bonding power is not so greatly dimin- ished. This clay was used several years ago by Mr. John Mahafa in the manufacture of drain tile. It is stated that the lack of demand for tile at that time caused the enterprise to be abandoned. On comparing the analysis of No. 32 with that of No. 33 an increase in silica from the limestone to the clay of nearly double may be noted. The lime element, however, has decreased 18.94 per cent. Clay No. 32 has a total shrinkage of 10 per cent. It loses 42 per cent in weight in drying and burning. The burned brickettes are pale yellow due to the presence of lime which destroys the coloring effects of the iron. The average tensile strength of 12 unbumed brickettes was 152 pounds per square inch. The minimum strength was 122 Plate XXVIII TAKING BRICK FROM OFF-BEARING, BELT OF AN END-CUT MACHIN CLAYS OF NORTHERN MISSISSIPPI. 177 pounds and the maximum 172 pounds. It has an absorption of 16.86 per cent. When mixed with 10 per cent of cinders and burned, it has an absorption of 14.28 per cent; when mixed with 10 per cent of coal, it has an absorption of 12.72 per cent. The clay at the top of the pit has suffered a still greater loss in soluble constituents and shows an increase in insoluble elements. The following analysis shows its composition: TABLE 49. ANALYSIS OF SURFACE CLAY, WEST POINT. No. 34 Moisture (H 2 O) 2.41 Volatile matter (C0 2 etc.) 7.66 Silicon dioxide (Si0 2 ) 73.70 Iron oxide (Fe 2 0 3 ) 11.14 Aluminum oxide (A1 2 0 3 ) 3.81 Calcium oxide (CaO) 1.04 Magnesium oxide (MgO) .00 Sulphur trioxide (SO 3 ) .21 Total 99.97 RATIONAL ANALYSIS. Clay substance 9.63 Free silica 69.22 Impurities 12.34 This clay probably contains a mixture of Lafayette sand and Columbia loam, both of which have been washed down from a neigh- boring elevation. The amount of impurities exceeds the amount of clay. The large per cent of free silica renders the clay non -plastic. However, it supplies non -plastic material which may be used for dilut- ing the more plastic clay below. The Welch-Trotter Brick Manufacturing Company operates a yard on the line of the Illinois Central Railroad at West Point about i mile south of the station. The plant was established in 1905. The clay used is mostly residual clay from the Selma chalk, though the upper portion may be in part Columbia loam. The pit has been opened to a depth of 7 to 8 feet. The lower clay is very plastic. A sample of clay analyzed from near the bottom of the pit gave the following results: 178 CLAYS OF MISSISSIPPI. TABLE 50. ANALYSIS OF CLAY USED AT THE WELCH-TROTTER BRICK PLANT, WEST POINT. No. 44 Moisture (H 2 O) 3.45 Volatile matter (CO 2 etc.) 5.58 Silicon dioxide (Si 02 ) 72.32 Iron oxide (Fe 20 s) 7.44 Aluminum oxide (AI 2 O 3 ) 8.74 Calcium oxide (CaO) 1.55 Magnesium oxide (MgO) .47 Sulphur trioxide (SO 3 ) .51 Total 100.06 RATIONAL ANALYSIS. Clay substance 22.11 Free silica 62.05 Impurities 9.97 The clay from the lower layers of the Welch-Trotter pit does not dry readily, and is used only when mixed with the upper leaner clay. The shrinkage of the lower clay is very excessive. The absence of non-plastic material of large grain permits a very slow transfer of water from the center of the brick. Thus the outside becomes dry and shrinks more rapidly than the center, thereby producing cracks. Two samples of clay from the middle portion of the bed show the following chemical composition: TABLE 51. ANALYSES OF CLAYS, WEST POINT. No. 45 No. 47 Moisture (H 2 O) Volatile matter (CO 2 ) . . . Silicon dioxide (Si 02 ) Iron oxide (Fe 20 s) Aluminum oxide (A1 2 0 3 ) Calcium oxide (CaO) Magnesium oxide (MgO) . Sulphur trioxide (SO 3 ) . . 3.95 3.10 5.12 3.75 71.45 76.86 5.00 9.50 11.68 3.75 1.45 1.25 .76 .45 .34 .34 Total 99.75 98.70 RATIONAL ANALYSIS. Clay substance 28.55 Free silica 57.73 Impurities 7.55 Clay No. 45 requires 17 per cent of water to render it plastic. It shrinks about 6§ per cent. It bums without cracking to a red CLAYS OF NORTHERN MISSISSIPPI. 179 color. The tensile strength of the raw brickettes is 92 pounds per square inch. The burned brickettes have a strength of 130 pounds per square inch. This clay has about the proper amount of clay substances and the proper physical properties to make a good clay for the manufacture of a stiff-mud brick. The thickness of the layer is not sufficient to warrant its exclusive use. Therefore a mixture of top, bottom and middle clay is used. Clay No. 47 is noticeable for its high silica content and the small amount of alumina. It has a peculiar texture and is somewhat light and spongy. Its total shrinkage is 5 per cent. It requires the addi- tion of 19 per cent of water for molding. The raw clay has a tensile strength of 140 pounds per square inch. The burned brickettes have strength of 138 pounds per square inch. A medium burned brickette absorbs 10.52 per cent of water. The tensile strength is high when the small amount of clay substance is considered. The amount of impurities in the clay is in excess of the clay substance. The clay from the top of the pit contains more silica and less alumina than the clay from the middle and lower portions of the pit. An analysis of a sample of the top clay is given below: TABLE 52. ANALYSIS OF SURFACE CLAY, WEST POINT. No. 40 Moisture (H 2 0) 3.50 Volatile matter (C0 2 ) 2.52 Silicon dioxide (Si0 2 ) 75.95 Iron oxide (Fe 2 0 2 ) 5.08 Aluminum oxide (Al 2 03 ) 9.62 Calcium oxide (CaO) 1.25 Magnesium oxide (MgO) .74 Sulphur trioxide (SO3) .34 Total : 99.00 RATIONAL ANALYSIS. Clay substance 24.33 Free silica 64.74 Impurities 7.41 The above mentioned clay may be molded by the addition of 18 per cent of water. The burned brickettes are red in color and free from cracks and checks. The raw clay has a tensile strength of 283 180 CLAYS OF MISSISSIPPI. pounds. The total shrinkage is about 6 per cent. The increase in tensile strength over the clay from the middle portion of the pit is noticeable. The increase is doubtless due to the greater amount of clay substance. CHICKASAW COUNTY. GEOLOGY. The eastern portion of Chickasaw County is underlain by the Ripley and Selma divisions of the Cretaceous. The western portion is under- lain by the Porter’s Creek and the W ilcox. The Lafayette, the residual Selma and the Columbia overlie the bed-rock formations. The clays used in the manufacture of brick are from these surface formations. CLAY INDUSTRY. Okolona . — At Okolona deposits of yellow clay, for the most part residual Selma, rest upon that formation. This clay is used by Haw- kins*and Hodges in the manufacture of brick. This brick plant was established in Okolona in 1895. The brick are molded in a stiff-mud machine of the auger-type. They are cut with an end-cut machine. The kilns in use are rectangular up-draft kilns of the clamp type. The clay in the pit is of two kinds: the upper is sandy, the lower is plastic and contains blue and red streaks. The limestone under- lying the clay at this point has the following composition: TABLE 53. ANALYSIS OF SELMA LIMESTONE, OKOLONA. Moisture (H 2 O) Volatile matter (CO 2 etc.) . . . Silicon dioxide (Si 02 > Iron oxide (Fe 20 s) Aluminum oxide (AI 2 O 3 ) Calcium oxide (CaO) Magnesium oxide (MgO) .... Sulphur trioxide (SO 3 ) Total No. 19 1.10 34.20 8.70 6.00 .00 45.62 1.72 1.11 98.45 Another sample of the limestone has the chemical properties indicated below: CLAYS OF NORTHERN MISSISSIPPI. 181 TABLE 54. ANALYSIS OF SELMA CHALK, OKOLONA. No. 12a Moisture (H 2 0) 6.35 Volatile matter (C0 2 etc.) 31.11 Silicon dioxide (Si0 2 ) 8.80 Iron oxide (Fe 2 Os) ,. 4.08 Aluminum oxide (Al 2 Os) 2.86 Calcium oxide (CaO) 45.51 Magnesium oxide (MgO) 0.36 Sulphur trioxide (SO 3 ) 0.38 Total 99.45 The bottom clay is very plastic and is derived from the Selma by the solvent action of surface waters. The decomposition of pyrite contained in the chalk forms iron concretions called “buckshot,” in the lower part of the clay bed. They are not uniformly distributed but are found in streaks in the lower layers and should be avoided, as they interfere with cutting and cause flaws in the brick unless crushed. Houston . — The Pope Brick Manufacturing Company established a plant at Houston in 1903. The clay used is red clay, belonging probably to the Lafayette. The brick are molded in a stiff -mud machine of the plunger type. The brick are dried by heating under covered sheds. The burning is done in rectangular up-draft kilns. The clay is plastic, especially in the bottom layers, and care must be exercised in order not to dry too rapidly. The use of the non -plastic surface loam serves to increase the speed of drying. New Houlka . — The New Houlka Brick Manufacturing Company’s plant was established at New Houlka in 1904. The clay is prepared in a disintegrator and tempered in a pug mill. It is molded in an auger-type stiff-mud machine. The brick are cut with an end-cut machine and burned in rectangular up-draft kilns. The stratigraphy of the clay pit is as follows: Section of Clay Pit , New Houlka. Feet 4. Yellow! loam 2-3 3. Gray clay, very plastic 4-5 2. Grayish clay with iron concretions (buckshot) 1 1 . Limestone with shells (Clayton) 182 CLAYS OF MISSISSIPPI. Clays Nos. 2 and 3 have very similar properties to the Porter’s Creek or Flatwoods clays. Since New Houlka lies within the edge of that area, these clays are probably residual clays from that group. Layer No. 4 may consist partly of this residual clay and partly of foreign material. A sample of clay from No. 3 has the composition recorded below: TABLE 55. ANALYSIS OF BRICK CLAY. NEW HOULKA. No. 96 No. 95 Moisture (H»0) Volatile matter (COj etc.) Silicon dioxide (SiOj) Iron oxide (FejOs) Aluminum oxide (AljOj). Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SOj) 3.86 4.00 3.60 6.30 75.85 71.75 5.45 -5.95 4.95 5.85 1.87 2.05 .49 .14 .04 .48 Total 96.11 96.52 RATIONAL ANALYSIS. Clay substance 12.52 14.79 Free silica 68.28 62.81 Impurities 7.86 8.62 No. 95 from No. 4 No. 96 from No. 3 The absorption of clay No. 96 is 12.96 per cent; tensile strength, raw, 75 pounds. The absorption of a mixture of Nos. 95 and 96 is 16 per cent; tensile strength, raw, 60 pounds; burned, 75 pounds; shrinkage, 5 per cent. CHOCTAW COUNTY. GEOLOGY. Choctaw County lies within the area of the Wilcox Eocene, with a small outcrop of Claiborne in the southwestern corner. The mantle rock belongs to the Lafayette and the Columbia. The surface clays have been used at Ackerman in the manufacture of brick. The plant is not now in operation. The brick were made by the soft-mud process and burned in scove kilns. There seems to be a suitable body of clay for the manufacture of brick just west of the Mobile, Jackson and Kansas City station. The clay is bluish in color and has a thickness of about 15 feet. An exposure of the Wilcox and later formations may be seen in a CLAYS OF NORTHERN MISSISSIPPI. 183 cut on the Illinois Central Railroad one-half mile east of Ackerman. At the bottom of the cut there are 10 feet of pink colored sand. Over- lying the pink sand there are 10 feet of orange sand with little partings of clay. Near the top there is a thin layer of ironstone which has been broken up, the pieces being turned at various angles. On the ^slopes there is a bed of yellow loam which decreases in thickness toward the top until at the apex there is not more than 1 foot of it. The best clays for brick making in this country are to be found in the second bottom deposits. Some of the upland loams may be used in the soft -mud process. COAHOMA COUNTY. GEOLOGY. The surface of Coahoma County is occupied by the recent alluvium deposited by the Mississippi River upon its flood plain. The rocks of the Wilcox formation underlie this alluvial deposit at a depth of from 25 to 50 feet. At a number of places in Coahoma County the dark “buckshot” clay of the alluvium has been burned successfully for road ballast. There are several short sections of roads upon which the ballast has been used with satisfactory results. The burned clay ballast is said to be much more economical than gravel. The cost per mile for the burned clay ballast is about $1,500. CLAY INDUSTRY. Clarksdale .— An experiment in road building carried on at Clarks- dale by the U. S. Bureau of Public Roads gave very satisfactory results. The experiment was made upon a piece of road having a length of 300 feet. The road was first plowed as deep as it was pos- sible for a four-horse team to pull the plow. It was then cross-fur- rowed and pieces of wood were placed across the furrows resting upon the crests of the intervening ridges. The wood was then cov- ered with clay and more .wood placed upon the surface of the clay. This wood was covered with more clay. Fires were then kindled in the furrows beneath the wood. The burning of the wood reduced the overlying clay to a “clinker.” After the clay had been burned it was rolled down and compacted forming a close, hard, non-plastic surface. The several items of cost were as follows: 184 CLAYS OF MISSISSIPPI. TABLE 56. COST OF BUILDING 300 FEET OF ROAD WITH BURNED CLAY BAL- LAST. CLARKSDALE. 30£ cords of wood at $1.30 per cord $39.65 20 loads of bark and chips at $0.30 6.00 Labor at $1.25 per day and teams at $3.00 per day 38.30 Total cost of 300 feet $83.95 Total cost per mile at this rate, $1,478.40. The clay ballast has not the wearing qualities of the hard chert gravel, such as the Tishomingo gravel, but with proper care it can be made very serviceable, and in a land of such paucity of good road metal and great abundance of timber this method of road making has its advantages. It is to be hoped that further experiments will be tried in the Delta and in other parts of the State, By the use of its convict labor the State could conduct experiments of this kind upon the roads on and near Sunflower farm, using the timber cut from the land in the process of clearing The alluvial clays of Coahoma County are used at Clarksdale for the manufacture of both brick and drain tile. The Clarksdale Brick and Tile Mfg. Company has opened a pit in which the following stratigraphical conditions exist: Section of Clay Pit , Clarksdale. Feet 5. Soil and sandy loam 7 4. Dark colored clay (buckshot) 8 3. Sandy loam 12 2. Sands 3 1. Gravel bowlders in bottom Samples of clay taken from beds Nos. 5 and 4 gave the results shown in analyses Nos. 62 and 61 respectively. TABLE 57. ANALYSES OF CLAYS USED BY THE CLARKSDALE BRICK AND TILE CO., CLARKSDALE. Moisture (H2O) Volatile matter (CO* etc.) Silicon dioxide (Si02) Iron oxide (Fe20s) Aluminum oxide (AI 2 O 3 ) . Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SO3) No. 62 No. 61 2.81 6.78 4.23 7.97 74.45 58.52 3.38 6.87 11.62 16.20 1.69 1.75 .94 .36 .43 .51 Total 99.55 98.96 CLAYS OF NORTHERN MISSISSIPPI. 185 RATIONAL ANALYSES. Clay substance Free silica Impurities No . 5 No. 4 29.39 40.98 60.89 39.47 8.44 9.49 The clay from No. 5 has a total shrinkage of 6§ per cent; tensile strength raw, 115 pounds; burned, 155 pounds; requires 19 per cent cf water. Clay from No. 4 has total shrinkage of 5 per cent; requires 18 per cent of water; tensile strength raw, 132 pounds; burned, 258 pounds. The clay is prepared by the use of a granulator and disintegrator and after being tempered n a pug mill is molded in an auger, stiff - mud machine. The clay from layer No. 4 contains more clay than sand. Its shrinkage is excessive and it can not be used alone in the manufacture of brick or tile; when mixed with the non-plastic ma- terial from the other layers of the pit it produces a good grade of ware. Careful selection of clay and mixing is necessary to obtain the best results. Whenever a large proportion of the plastic clay is used difficulties of rapid drying of the wares are greatly increased. The burned brickettes have an absorption of 12.96 per cent. The Rheinhart firm of Clarksdale also operates a plant for the manufacture of brick and drain tile. In the clay pit which they have opened in the alluvial deposit the following layers are encountered: Section of Rheinhart Clay Pit , Clarksdale. Feet 4. Soil and sandy loam (top) 3 3. Sandy clay 8 2. Dark clay (buckshot) 5 1. Sand in bottom The analysis of clay from layer No. 2 is here given: TABLE 58. ANALYSIS OF BUCKSHOT CLAY USED AT THE RHEINHART BRICK AND TILE FACTORY, CLARKSDALE. No. 63 Moisture (H 2 O) 6.70 Volatile matter (CO* etc.) 8.31 Silicon dioxide (SiOj) 59.47 Iron oxide (Fe 203 ) 7.25 Aluminum oxide (AI 2 O 3 ) 14.00 Calcium oxide (CaO) 1.50 Magnesium oxide (MgO) .83 Sulphur trioxide (SO 3 ) .43 Total 98.49 186 CLAYS OF MISSISSIPPI. RATIONAL ANALYSIS. Clay substance • 35.42 Free silica 7 40.03 Impurities 10.01 The gray “buckshot” clay is mixed with a more sandy clay for the manufacture of brick and drain tile. The amount of clay sub- stance permits the addition of considerable non-plastic material without destroying the bonding power. In the manufacture of the smaller size of tile a horizontal machine is used, but for the larger sizes a vertical attachment is employed. The brick and tile are burned in kilns of the beehive type. DE SOTO COUNTY* GEOLOGY. The extreme western part of De Soto County lies within the allu- vial plain of the Yazoo basin. The remainder of the country lies at a higher level and has a much more rugged topography. The hilly portion is covered with surfacial deposits of Lafayette, Loess and Columbia. The sub-formation of the county is the upper portion of Hilgard’s Lignitic (Wilcox). CLAY INDUSTRY. Lake View . — At Lake View, a station on the Yazoo and Mississippi Valley Railroad, one-half mile south of the Tennessee line, the flood plain meets the bluffs. At a point where the railroad makes a cut through the bluffs the following section is revealed: Section of Loess and Lafayette One-Half Mile South of Lake View. Feet 4. Soil 1 3. Brownish sandy loam (Loess) 10 2. Gravel and sand (Lafayette) 5 1. Gravel and conglomerate (Lafayette) 10 The gravels of Nos. 1 and 2 are largely white, yellow and blue flints. In some places they are cemented together, forming masses of pudding stone, or conglomerate of considerable size. The cement- ing substance is limonite. No. 1 is Lafayette and No. 2 is probably Lafayette, though the latter may be Natchez. No. 3 is Loess and its derivative, though no concretions' or gastropod shells were found in it. CLAYS OF NORTHERN MISSISSIPPI. 187 A sample of clay from No. 2 was collected for analysis and gave results as follows: TABLE 59. ANALYSIS OF CLAY. LAKE VIEW. No. 50 Moisture (H 2 O) 1.31 Volatile matter (CO 2 etc.) 5.28 Silicon dioxide (Si02) 75.33 Iron oxide (Fe20s) 5.60 Aluminum oxide (A1 2 Oj) 7.80 Calcium oxide (CaO) 1.25 Magnesium oxide (MgO) 1.19 Sulphur trioxide (SO*) .60 Total 98.36 RATIONAL ANALYSIS. Clay substance 19.73 Free silica 66.16 Impurities 9.64 The physical character of No. 2 is as follows: The total shrinkage is 3J per cent; water required for plasticity, 17 per cent; tensile strength raw, 65 pounds per square inch; burned, 83 pounds; absorption, 13.33 per cent; color, cherry red. The clay lacks the plas- ticity essential to stiff-mud brick, but it may be used for soft-mud brick, or, by mixing with the more plastic “buckshot” clays of the bottom, it may be used by the stiff -mud methods. About one mile south of Lake View is located the works of the Valley Brick and Tile Company. The products of their plant are brick, hollow blocks and drain tile. The brick and blocks are molded in a stiff -mud machine of the horizontal auger type. The brick are cut by an automatic side-cut machine. Two types of kilns are used, namely, an up-draft kiln of the rectangular, clamp type and a down- draft beehive kiln. The clay used is obtained from alluvial deposits of the Yazoo basin. It bums to a red color but explodes and flies to pieces if the heat be applied too rapidly. In air-drying it shrinks 15 per cent, but its total shrinkage after burning is only 10 per cent, so that the air shrinkage is partly compensated by swelling in burning. The water required to render it plastic is 22 per cent. In the raw state the air- dried brickettes have a tensile strength of 183 pounds. When burned they exhibit a strength of 193 pounds. The chemical composition of a sample of the clay is as follows: 188 CLAYS OF MISSISSIPPI. TABLE 60. ANALYSIS OF ALLUVIAL CLAY. LAKE VIEW. No. 51 Moisture (H 2 0) 5.15 Volatile matter (CO* etc.) 11.70 Silicon dioxide (SiO*) 58.92 Iron oxide (Fe 2 03 ) 7.45 Aluminum oxide (A1 2 0») 11.75 Calcium oxide (CaO) 1.10 Magnesium oxide (MgO) 1.01 Sulphur trioxide (SO3) .48 Total 97.56 RATIONAL ANALYSIS. Clay substance 29.72 Free silica 45.11 Impurities 10.04 Hernando . — At Hernando the surface formations are Lafayette and Columbia. The latter seems to be a modified, or at least a partly residual, form of the Loess. An outcrop in a ravine south of the station reveals the following stratigraphy: Section of Ravine Near Hernando. Feet 5. Soil 1 4. Brown loam, light in color 6 3. Brown loam, dark in color 6 2. Gravel and red sand 10 1. Reddish clay The rocks of Nos. 1 and 2 belong to the Lafayette, while those of 3 and 4 are Columbia. A sample of clay from No. 4 has the following physical properties: It requires 10 per cent of water to render it plastic. The tensile strength of the raw clay is 90 pounds; when soft burned its strength is only 85 pounds. It bums to a red color. The total shrinkage is only about 1 per cent. The loss of weight in drying and burning is 18 per cent. The burned brickettes have an absorption of 10.76 per cent. GRENADA COUNTY. GEOLOGY. The subformation of the eastern part of Grenada County is the Wilcox (Lagrange). The Silicious Claiborne, or Tallahatta buhrstone, underlies the western part of the county. The mantle formations are the Lafayette, the Loess and the Columbia loam. CLAYS OF NORTHERN MISSISSIPPI. 189 CLAY INDUSTRY. Grenada . — At Grenada the Columbia loam clay is used in the manufacture of brick. The Carl Brick Company operates a plant south of the Illinois Central Railroad station. Brick are manufactured by the soft-mud process and are burned in rectangular, up-draft kilns of the scove type. About 8 feet of clay is exposed in the pit. The lower portion is much more plastic than the upper portion. Two samples of the clay have the following chemical properties: TABLE 61. ANALYSES OF COLUMBIA CLAY. GRENADA. Moisture (H 2 0) Volatile matter (C0 2 etc.) Silicon dioxide (Si0 2 ) Iron oxide (Fe 2 03 ) Aluminum oxide (Al 2 03 ) . . Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SO 3 ) No. 79 1.91 2.31 3.34 2.83 73.44 73.11 5.97 5.62 10.35 10.44 1.87 1.15 1.12 .98 .13 .18 Total 98.14 96.62 RATIONAL ANALYSIS. Clay substance 26.18 26.41 Free silica 61.27 60.84 Impurities 9.09 8.93 The more sandy upper portion of the clay is mixed with the lower plastic portion in the manufacture of brick. The sandy clay has a total shrinkage of 5 per cent. It requires the addition of 17 per cent of water to render it plastic. The tensile strength of the raw clay is 55 pounds per square inch. When burned it has a strength of 94 pounds per square inch. The burned brickettes have an absorp- tion of 15.57 per cent. The lower clay requires 17.9 per cent of water to render it plastic. The total shrinkage is 7 per cent. The tensile strength in the raw state is 66 pounds per square inch. The burned brickettes have a strength of 127 pounds per square inch. A shale-like clay outcrops along the banks of the Yalobusha River at Grenada. At the Bledsoe Brick Company’s j)lant this clay has a thickness of 40 feet, as shown by the record of an artesian well drilled by Mr. Bledsoe. 190 CLAYS OF MISSISSIPPI TABLE 62. RECORD OF ARTESIAN WELL AT THE BLEDSOE BRICK YARD, GRENADA. Thickness Depth Yellow loam and gray clay 9 feet 9 feet White sand, water bearing 12 “ 21 “ Dark clay shale 40 “ 61 “ Sand and shale (water at 200 feet) 160 “ 200 “ Greenish sand and clay 25 “ 225 “ Sand and clay (artesian water at 465 feet) . 240 “ 465 “ Sand, and at 475 feet a hard flint rock 10 “ 475 “ Sand and water 25 “ 500 “ The clay is dark in color and of low specific gravity. The follow- ing analysis shows the chemical composition: TABLE 63. ANALYSIS OF SHALE-CLAY, GRENADA. No. 56 a Moisture (HjO) 5.91 Loss on ignition (CO* etc.) 8.75 Silica (SiOj) 61.80 Ferric oxide (FejOj) 3.88 Alumina (Al,O a ) 16.50 Lime (CaO) 1.00 Magnesia (MgO) .25 Sulphur trioxide (SOs) .19 Total 98.28 RATIONAL ANALYSIS. Clay substance 41.74 Free silica 42.40 Impurities 5.82 Mr. O. F. Bledsoe thinks this clay is suitable for the manufacture of drain tile, but he has not yet given, it a trial. The Bledsoe Brick and Tile Company was established in 1901. They have the requisite machinery for the manufacture of brick by the so ft -mud, the stiff - mud or the dry -press process. The clay so far used is a surface clay, having a thickness of about 9 feet. The pit exhibits the following section : Section of Clay Pit at Grenada. Feet 4. Brown sandy loam 2 3. Whitish clay 4 2. Dark colored joint clay 1. White sand 12 The pit is located on the second bottom of the Yalobusha River. CLAYS OF NORTHERN MISSISSIPPI. 191 Holcomb . — At Holcomb, Fred Gulo established a brick plant in 1906. The brick are molded in a soft-mud machine operated by horse power. They are dried in the sun in an open yard. Some of the brick are repressed before being burned in up-draft, scove kilns. The clay used is a surface clay which is tempered by the use of sand. It is probably Columbia in age. The burned brick are red in color. HINDS COUNTY. GEOLOGY. The formations occupying the subsurface of Hinds County are Jackson, Vicksburg, and Grand Gulf. All of these formations belong to the Tertiary period. The Lafayette and the brown loam phase of the Columbia and the alluvium of the Pearl River valley form the unconsolidated sediments of the mantle rock. The Columbia loam forms the surface of the greater part of the country, the Lafayette occupying the higher isolated areas. CLAY INDUSTRY. Jackson . — At Jackson the clay at the base of the brown loam is being used in the manufacture of brick. The W. B. Taylor plant was established in 1881, and has been in continuous operation since that time. The clay pit has the following layers: Section of the Taylor Clay Pit , Jackson. Feet 3. Soil 1 2. Clay, brown, jointed in lower part 6-8 1. Yellowish clay with gravel in upper part 4 The chemical composition of a sample of clay from No. 2 is given below: TABLE 64. ANALYSIS OF BRICK CLAY, JACKSON. No. 73 Moisture (H 2 O) 1.80 Volatile matter (CO 2 etc.) 4.37 Silicon dioxide (Si02) 75.21 Iron oxide (Fe20a) 5.47 Aluminum oxide (AI2O3) 10.71 Calcium oxide (CaO) .87 Magnesium oxide (MgO) .93 Sulphur trioxide (SO 3 ) .52 Total 99.88 RATIONAL ANALYSIS. Clay substance 27.09 Free silica 62.62 Impurities 7.79 192 CLAYS OF MISSISSIPPI. The above mentioned clay is usee], in the manufacture of brick. The whole section of the clay is taken and mixed. The lower portion of the clay has a joint structure, the faces of the blocks being covered with a white efflorescence. This may be a deposit of gypsum brought up from the underlying clay by circulating waters. The brown clay has an air shrinkage of 3^ per cent. The tensile strength of the raw clay is 50 pounds per square inch. The clay requires an addition of 17 per cent of water for plasticity. The clay in No. 1 of the Taylor clay pit has the following chemical composition: TABLE 65. ANALYSIS OF BRICK CLAY. JACKSON. No. 72 Moisture (H 2 0) 4.25 Volatile matter (C0 2 etc.) 8.01 Silicon dioxide (Si0 2 ) 67.72 Iron oxide (Fe 2 Os) 5.51 Aluminum oxide (Al 2 Oa) 10.86 Calcium oxide (CaO) .85 Magnesium oxide (MgO) .70 Sulphur trioxide (SOj) .54 Total ... 98.44 RATIONAL ANALYSIS. Cla y substance 27.47 Free silica 12.77 Impurities 7.60 The gravel lying on this clay is probably Lafayette. The clay which rests upon the Jackson is probably residual clay from that for- mation. It has a total shrinkage of 8 per cent. It requires 17 per cent of water for plasticity. Its tensile strength raw is 75 pounds per square inch; burned, it has a strength of 87 pounds. The absorption of the burned brickettes is 11.11 per cent. The Bullard Brick Mfg. Company also operates a plant at Jack- son. They use the brown loam clay, which has a thickness varying from 6 to 9 feet (see Plate XXXV B). The clay contains gravel at the base and rests upon a stiff plastic clay which belongs to the Jackson for- mation. This company used a soft-mud machine for about three years, but abandoned its use because of excessive shrinkage in the clay. The plant was established in 1899. The brick are molded in a stiff-mud machine of the auger type. -The brick are cut by the use of Plate XXIX, A. POWER HOUSE OF THE BULLARD BRICK PLANT, JACKSON. B. CLAY PIT OF THE BULLARD BRICK PLANT, JACKSON, CLAYS OF NORTHERN MISSISSIPPI. 193 an automatic end-cut machine. The brick are dried in covered sheds; some are stacked and others placed on pallets. They are burned in up-draft kilns of the clamp type. The brown loam, which is doubtless a modified form of the Loess, is probably not thicker than 20 feet anywhere in the county. It is the best brick clay in the county, but is not of the same quality in all parts of the county. In some deposits it lacks sufficient bonding power. In nearly all places it presents two phases, a loam phase in the upper part and a clay phase in the lower part of the deposit. The clay phase may be but poorly represented, in which case the deposit will not be suited to the manufacture of brick. HOLMES COUNTY. GEOLOGY. Holmes County lies within the area which is underlain by the Claiborne group. The Tallahatta buhrstone forms the bed-rock of the northern part of the county, and the “Claiborne Calcareous” the southern pa,it. The principal mantle rock formations belong to the Lafayette, the Loess, the Columbia and the Alluvium of the Yazoo delta. CLAY INDUSTRY. Lexington . — In the northern part of the town of Lexington, the stratigraphy of some of the surficial formations is revealed in numerous gullies or gulches. The soft, unconsolidated character of the sedi- ments has developed a “bad land” type of topography. The general stratigraphic conditions are given below: Section of the Lafayette , Lexington. Feet 6. Soil 1 5. Brownish colored loam and clay 6-10 4. Orange sand with white sandy clay gravel 10-15 3. White and purple sand and clay with small gravel. . . . 6-10 2. Larger gravel with some sand 3-5 1. Cross-bedded reddish sand 3-6 Layer No. 5 is doubtless Columbia loam. The remaining layers below belong to the Lafayette. These layers vary in thickness and composition from outcrop to outcrop. The gravels are for the most 194 CLAYS OF MISSISSIPPI pajt brown cherts, though there are some white and blue cherts, and some transparent quartz pebbles. Some of the cherts are fossiliferous. The shapes of some are irregular, but the majority are smooth and well rounded pebbles. The size of the pebbles vary from the size of a pea to a little larger than the size of a man’s fist. The larger sizes are not numerous. The irregularity in the bedding of the gravel may be seen from figure 14. ^ _ 1 ’ .j £] ^ \ •: {-j , FIGURE 13. SECTION OF THE LAFAYETTE, LEXINGTON ! C~N X) r* s o o 0 0 0 '\- • O * r\ o % VoX • 0 1 0 o ' • 1 'O ^ ' .' O'- •=> \ •O VPX ? Q X A 0 . 0 hfl'o, • v -o°,^ 0 & o/ ■ , b . b 0 CJ - O |0 o V'o^oV^QW;: I ^ 0 *) ' ^ ^ A ^ f\ 0 / o oXf io °o^#o«>o^vv O 5 0 . ^ , 0 A XXPX '■ X p^vOo^ <5 V^o°| itf/Jd} X ' ^ oX '^ /, o T •'>) ^ X / 0; <>, '0 ^-o \^o \ i aXci- o XX •i ^6V° AXo.o^ Xx . aX / 1 pVo X; ' J. ^ vO ^ r ( 0 'X * V ‘ X ^Q °’4 . .Xo ®/ 0 Poo'; of FIGURE 14 . CROSS BEDDING IN THE LAFAYETTE, LEXINGTON. 196 CLAYS OF MISSISSIPPI. A sample of clay from layer No. 5 has the following composition: TABLE 66. ANALYSIS OF COLUMBIA CLAY, LEXINGTON. No. 59 Moisture (HiO) 1.56 Volatile matter (CO* etc.) 4.14 Silicon dioxide (SiC> 2 ) 75.65 Iron oxide (FejO*) . 6.20 Aluminum oxide (A1*0») 8.70 Calcium oxide (CaO) 1.50 Magnesium oxide (MgO) 1.60 Sulphur trioxide (SO*) .26 Total 99.31 RATIONAL ANALYSIS. Clay substance 22.01 Free silica 65.42 Impurities 9.26 Clay No. 59 shrinks about 3 per cent in drying and burning. It requires the addition of 16 per cent of water to render it plastic. The tensile strength of the raw clay is 58 pounds per square inch. When burned it has a strength of 95 pounds per square inch. When allowed to dry in the open air it cracks badly. It lacks bonding power and could be used only by mixing with a more plastic clay. Durant . — The Love Wagon Manufacturing Company has operated a brick plant at Durant since 1893. The first clay pit and yard was located east of the line of the Illinois Central Railroad. New machinery was installed in this yard in 1897. In 1905 this yard was abandoned and a new one opened in the western part of the town on a spur of the railroad. The yard has been greatly enlarged and new machinery installed. The clay pit has been opened to a depth of 8 or 10 feet. The clay is brownish yellow in color, but contains streaks of gray clay which contain ironstone concretions of small size. Water is supplied to the plant from an artesian well. The record of this well shows a thickness of 40 feet for the surface formation. At a depth of 7 to 8 feet a hard stratum was encountered. Underlying the clay is a bed of sand. In the old pit the sand bed has a thickness of about 15 feet. Ironstone pebbles are very abundant in the lower part of the bed. § The clay is prepared in a granulator and disintegrator. It is Plate XXX. B. UP-DRAFT CLAMP KILNS, DURANT. CLAYS OF NORTHERN MISSISSIPPI. 197 tempered in a pug mill and molded in a stiff -mud machine. The brick are burned in rectangular up-draft kilns. A waste heat dryer is being installed. KEMPER COUNTY. GEOLOGY. The northeastern part of Kemper County has for its subformations Cretaceous strata belonging to the Selma and Ripley epochs. The remainder of the county is occupied by Eocene rock. The mantle formations are Lafayette, Columbia and the residual deposits of the bed-rock. CLAY INDUSTRY. Wahalak . — At Wahalak the sticky Flatwoods clay rests upon a hard rock, probably sandstone. On Wahalak Creek, 1 mile south of Wahalak, there is exposed the following section: Section on Wahalak Creek , One Mile South of Wahalak. Feet 3. Yellowish-red clay 6 2. Shally, friable sandstone 3 1. Blue limestone 3 A sample of clay from the well of D. V. Porter in Wahalak has an air shrinkage of 10 per cent and a tensile strength,, raw, of 112 pounds per square inch. When burned its strength is 170 pounds. It requires 20 per cent of water for plasticity. The burned brickettes absorb 11.23 per cent of water. Mixed with 10 per cent coal the absorption is 12.5 per cent. Total shrinkage is 4 per cent; the water required for plasticity is 14 per cent. The raw clay has a tensile strength of 77 pounds per square inch; when burned its strength is 222 pounds. When mixed with 10 per cent of Selma clay from Agricultural and Mechanical College campus the absorption is 10 per cent; has a tensile strength, raw, of 111 pounds per square inch, and when burned 105 pounds per square inch; its air shrinkage is only 5 [per cent; the amount of water required for plasticity is 14 per cent. LAFAYETTE COUNTY. GEOLOGY. Lafayette County lies wholly within the Wilcox division of the Tertiary. Resting upon the clays and sands of this formation are 198 CLAYS OF MISSISSIPPI. £* fc\ the Lafayette sand and clays and the Columbia loams. Many out- crops of fine pottery clays are found in the Wilcox in this county. The chemical composition of some of these clays are given in the table below : TABLE 67. ANALYSES OF CLAYS FROM THE WILCOX, LAFAYETTE COUNTY. No. 1 No. 2 No. 3 No. 4 No. 5 Moisture (H*0) .69 1.14 1.16 .90 1.64 Volatile matter (CO* etc.) . ... 8.20 9.11 10.14 8.35 8.99 Silicon dioxide (SiO*) . .. 60.00 57.79 51.88 60.40 57.48 Iron oxide (Fe*0*) .75 2.98 3.53 1.32 2.43 Aluminum oxide (Al*Oj) ... 27.80 26.03 30.64 27.68 26.94 Calcium oxide (CaO) 1.38 .44 .58 1.08 .78 Magnesium oxide (MgO) .00 .10 .60 .00 .27 Sulphur trioxide (SO*) 20 .24 .00 .00 .20 Total ... 99.02 97.83 98.53 99.73 98.73 RATIONAL ANALYSES. Clay base ... 70.45 65.97 77.65 70.15 68.27 Free silica ... 17.35 17.85 4.87 17.93 16.15 Fluxing impurities ... 2.33 3.52 4.71 2.40 3.48 No. 1 is from Oxford, about 3 blocks east of the courthouse. No. 2 is from the street near the colored schoolhouse in Oxford. No. 3 is from Mr. Russell’s farm, -3 miles northeast of Oxford. No. 4 is from the Tubbs farm, 3 miles south of Oxford. No. 5 is from the Wyley farm, 6 miles southwest of Oxford. CLAY INDUSTRY. College Hill Station . — The Brown loam clay is used at College Hill station, north of Oxford, by the Oxford Brick and Tile Company in the manufacture of pressed brick. The plant was first established south of Oxford near the oil mill, but the thickness of the clay was not adequate and the plant was moved to College Hill station. The plant was established in 1904. The Brown loam of the county, by proper selection and mixture, may be used in the manufacture of brick by the soft-mud, stiff -mud and dry-press methods. Processes of denudation have removed the loam in many places to such an extent that the thickness is not sufficient to warrant the establishment of brick plants at such points. There are two phases of the loam, a top sandy phase and bottom clayey phase. The latter in some places is very poorly represented Plate XXXI. PUBLIC BUILDING AT DURANT BUILT OF MISSISSIPPI PRESSED BRICK. CLAYS OF NORTHERN MISSISSIPPI. 199 and such places are undesirable localities for the manufacture of brick by either the stiff-mud or dry-press method. The white clays of the Wilcox furnish material for the manufacture of' white or spotted brick and a fine grade of stoneware. LAUDERDALE COUNTY* ' GEOLOGY* The bed-rock formations of Lauderdale County are of Tertiary age. The strata represented are the Wilcox and the Claiborne Both of these formations contain beds of clay. The Wilcox (Lagrange) contains beds of pottery clays. The mantle rocks are the Lafayette and the Columbia. CLAY INDUSTRY* Lockhart . — The Wilcox clays are utilized at Lockhart in the manu- facture of stoneware by the Wedgewood Stoneware Company. The clay is grayish-white and has the following chemical composition: TABLE 68* ANALYSIS OF WILCOX STONEWARE CLAY, LOCKHART. Moisture (H 2 O) Volatile matter (CO 2 etc.) Silicon dioxide (Si 02 ) Iron oxide (Fe 20 s) Aluminum oxide (AI 2 O 3 ) . Calcium oxide (CaO) Magnesium oxide (MgO) . . No. 71 3.14 7.20 58.05 1.05 27.79 2.00 .25 Total 99.48 RATIONAL ANALYSIS. Clay base 70.42 Free silica 15.42 Fluxing impurities 3.30 The Lockhart clays have been used in Meridian in the manufacture of brick. The brick are said to be extremely hard and to approach vitrified paving brick in physical properties. The Columbia loam has been used at Lockhart in the manufacture of brick by Mr. B. R. Brown. The brick are red in color. They are burned in up -dr aft kilns of the scove type. 200 CLAYS OF MISSISSIPPI. A sample of gray clay from the Wilcox formation on Mr. Brown’s farm at Lockhart has the following chemical composition: TABLE 69. ANALYSIS OF WILCOX CLAY, LOCKHART. No 72a Moisture (HjO) 4.29 Volatile matter (CO 2 etc.) 7.74 Silica (SiOj) 58.21 Iron oxide (FejOg) - *.83 Aluminum oxide (AI 2 O 3 ) 27.23 Calcium oxide (CaO) .65 Magnesium oxide (MgO) .41 Total 99.36 RATIONAL ANALYSIS. Clay substance 69.00 Free silica 16.44 Impurities 1.89 Meridian . — At Meridian the Columbia clay is used in the manu- facture of brick by the Bonita Manufacturing Company. The clay is prepared by the use of a granulator and tempered in a pug mill. The brick are molded in an end-cut, auger-type, stiff-mud machine. The brick are burned in rectangular updraft kilns. A sample of the tempered clay has the following composition: TABLE 70. ANALYSIS OF BRICK CLAY, MERIDIAN. NOm 93 Moisture (H 2 O) 3.72 Volatile matter (CO 2 etc.) 5.34 Silicon dioxide (Si 02 ) 71.58 Iron oxide (Fe 20 s) 6.95 Aluminum oxide (AI 2 O 3 ) 10.77 Calcium oxide (CaO) .50 Magnesium oxide (MgO) .19 Sulphur trioxide (SO 3 ) trace Total 99.05 RATIONAL ANALYSIS. Clay substance 27.23 Free silica 55.12 Fluxing impurities 7.64 LEE COUNTY. GEOLOGY. The Selma chalk forms the bed-rock of Lee County. It varies in thickness from a few feet on its eastern border to 600 feet on its CLAYS OF NORTHERN MISSISSIPPI. 201 western border. The surface formations are isolated areas of the Lafayette, and the residual clay of the Selma and the Columbia loam. The clays of these mantle rocks are being utilized in the manufacture of brick at Baldwyn, Saltillo, Verona and Nettleton. Brick were also manufactured at Tupelo. CLAY INDUSTRY. Baldwyn . — At Baldwyn, the Baldwyn Brick and Tile Company has opened a pit containing the following layers: Section of Pit of the Baldwyn Brick & Tile Co., Baldwyn. Feet 4. Soil 1 3. Sandy loam or sand 1 2. Plastic red and blue clay 6-8 1. Sand (depth in well) 7 The bottom portion of No. 2 contains small ironstone concretions, “buckshot.” The clay from this layer has a total shrinkage of 8 per cent. The raw clay has a tensile strength of 188 pounds per square inch. The soft-burned brickettes have a strength of 130 pounds per square inch. The addition of 20 per cent of water is required for plasticity. When mixed with 10 per cent of coal the clay has a total shrinkage of 6 per cent. Its tensile strength, raw, is 153 pounds. When hard burned it has a strength of 187 pounds per square inch. The amount of water required for plasticity is 20 per cent and the loss in burning 10 per cent. When mixed with 10 per cent of cinders it has a total shrinkage of 6 per cent and requires 16 per cent of water to render it plastic. It loses 8 per cent of its weight in burning. The tensile strength of the raw clay is 138 pounds per square inch. When burned it has a tensile strength of 244 pounds per square inch. The composition of a sample of the clay is given below: TABLE 71. ANALYSIS OF CLAY USED BY THE BALDWYN BRICK AND TILE CO., BALDWYN. No. 114 Moisture (H 2 O) 3.60 Volatile matter (CO 2 ) .04 Silicon dioxide (Si 02 > 72.72 Iron oxide (Fe 20 a) 3.96 Aluminum oxide (AI 2 O 3 ) 12.56 Calcium oxide (CaO) 6.90 Magnesium oxide (MgO) .27 Sulphur trioxide (SO*) .08 Total 100.11 202 CLAYS OF MISSISSIPPI. RATIONAL ANALYSIS. Clay substance 41.75 Free silica 43.52 Impurities 11.20 Saltillo . — At Saltillo the plant of the Saltillo Brick Manufacturing Company is located about i mile south of the Mobile and Ohio Railroad station. This company uses a surface clay in the manufacture of brick by the stiff-mud process. The machine is of the plunger type. No disintegrator or pug mill is used in preparing the clay. The brick are burned in rectangular up-draft kilns. Red is the prevailing color of the burned brick. The clay in the upper part of the pit is a sandy red clay overlying a sandstone. Both of these layers are probably of Lafayette age. The lower part of the pit is occupied by a more plastic clay which is probably residual Selma, since the latter underlies it. The record of the well at the brick plant shows the thickness of the Selma at this point to be about 330 feet. The lower clay is too plastic to be used alone. When mixed in the proper proportion with the sandy upper clay it makes a good brick. Verona . — The Verona Brick and Tile Company’s plant is located about i mile north of the Mobile and Ohio Railroad station at Verona. Two varieties of surface clay are employed in the manufacture of brick. The bottom of the pit rests upon the Selma chalk. Overlying this bed is a plastic clay which has doubtless been derived from the Selma by decomposition processes. Resting upon the lower clay is a red sandy clay which probably belongs to the Lafayette. In the manufacture of brick these two clays are mixed. The clay is tempered in a horizontal pug mill and molded in a stiff-mud machine of the auger type. The cutter is a side-cut machine. The brick are dried in rack and pallet driers. They are burned in up-draft kilns of the clamp variety. The auger motion produces laminations in this clay unless it has been carefully tempered. When too large a proportion of the bottom clay is used the difficulties of drying are greatly augmented. Thorough disintegration and mixing are essential to the best results. Gathering the clay too close to the limestone surface may result in inclusions which cause flaws in the brick. CLAYS OF NORTHERN MISSISSIPPI. 203 Nettleton . — The Nettleton Manufacturing Company operates a brick plant at Nettleton. The clay used is from a surface deposit consisting of clay, loam and sand. It is probably of Lafayette age for the most part. The total thickness of the formation is about 20 feet; as is shown by well records in the town. The upper portion consists of yellowish loam, below which there is a sandy layer, then a fat jointed clay containing sandy streaks. The clay is prepared by the use of a granulator and a disintegrator. It is then tempered in a pug mill and molded in a soft -mud molding machine, operated by steam power. The molds contain six bricks. They are sanded to prevent the clay from sticking. The brick are placed upon pallets, which are placed on racks under covered sheds. The brick are burned in rectangular up-draft kilns. LEFLORE COUNTY. GEOLOGY. The alluvium of the Yazoo -Mississippi flood plain occupies the surface of the greater part of Leflore County. Beneath this over- burden, which has an average thickness of about 50 feet, lies the Claiborne formations. Two rather distinct types of the alluvium are recognizable. The first type is a sandy loam which occupies the sur- face bordering the streams. The second type is a black, sticky clay which occupies the surface of the inter-stream areas and is called locally “buckshot” land. Vertically the one type may succeed the other within a few feet. The change from one type to the other in vertical and horizontal succession was produced by the shifting or meandering of the depositing stream. When the stream overflows, the water, which passes from the stream’s course out over the flooded plain, begins to lose its velocity as it leaves the banks and to drop its load, the heavier particles being deposited first, the finer clay particles being carried to the inter-stream areas. The clays of this alluvial deposit are used in the manufacture of brick at Greenwood, in Leflore County. CLAY INDUSTRY. Greenwood . — The Success Brick and Tile Company of Greenwood is using clay from a pit which has the following stratigraphic relations: 204 CLAYS OF MISSISSIPPI. Section of Clay Pit at Greenwood. 4. Joint clay, black to gray in color (top) 3. Very sandy clay . 2. Reddish tinged clay 1. Blue clay Feet 5 4 4 6 The full thickness of No. 1 is not exposed. Chemical analyses of layers Nos. 1 and 2 were made with the results given in Table No. 72. TABLE 72. ANALYSES OF CLAYS, GREENWOOD. Moisture (H*0) No. 48 5.52 No. 98 3.22 No. 99 5.75 Volatile matter (CO* etc.) 4.75 3.06 6.55 Silicon dioxide (SiO*) 72.25 73.40 59.32 Aluminum oxide (Al*Oj) . . 8.44 6.81 11.45 Iron oxide (Fe* 03 ) 4.19 10.62 Calcium oxide (CaO) 1.00 1.12 1.50 Magnesium oxide (MgO) . . . 63 .44 1.37 Sulphur trioxide (SO*) 17 .17 2.98 Total 99.32 92.41 99.54 Clay substance RATIONAL ANALYSES. 17.22 26.86 Free silica 59.34 65.40 46.84 Impurities 5.92 12.48 Analysis No. 48 is from bed 1 of the above section; No. 98 is from bed 2, and No. 99 is from bed 3. The different layers of clay from the above mentioned pit are mixed together in the manufacture of brick. The brick are molded in a stiff -mud auger-type machine with an end-cut. The elevating cars are used in the yard. The clay is prepared in a granulator and pug mill. Mr. W. O. Bacon also owns and operates a brick plant at Green- wood. He uses a dark, alluvium clay. The thickness of the clay in the pit is about 8 feet ; all of the clay is utilized. The brick are molded in a steam-power machine of the soft-mud type. They are dried in sheds in which they are placed on pallets. The brick are burned in up-draft kilns of the clamp type. An analysis of the clay was made with the results shown in No. 99. Some of the clay in the pit is more siliceous than the sample taken. M inter City . — At Minter City the Cowgill Drain Tile Manufacturing Company uses the alluvium clay in the manufacture of brick and drain tile. Their pit is opened to a depth of 8 feet, the clay being used from Plate XXXII B. STRATIFIED LAFAYETTE WITH TALUS, RAILROAD CUT, NEWTON, CLAYS OF NORTHERN MISSISSIPPI. 205 top to bottom. The clay varies somewhat in composition from top to bottom of the pit. Three samples of clay from the pit were analyzed with the follow- ing results: No. 55 from near the top, No. 56 from the middle portion, and No. 57 from the bottom TABLE 73. ANALYSES OF ALLUVIAL CLAYS. MINTER CITY. No. 55 No. 56 No. 57 Moisture (H 2 O) 5.00 4.47 3.75 Volatile matter (CO 2 etc.) . . , 10.81 8.17 7.75 Silicon dioxide (Si 02 ) 63.27 62.18 65.66 Iron oxide (Fe 20 s) 6.32 8.20 5.40 Aluminum oxide (AI 2 O 3 ) 10.43 12.80 10.90 Calcium oxide (CaO) 1.10 1.50 1.35 Magnesium oxide (MgO) . . . . 94 .79 1.01 Sulphur trioxide (SO 3 ) 48 .31 .61 Total 98.25 98.42 96.24 RATIONAL ANALYSES. Clay substance 26.36 32.38 27.57 Free silica 52.02 47.13 52.85 Impurities 8.84 10.80 8.38 Clay No. 55 requires the addition of 20 per cent of water to render it plastic. It has a total shrinkage of about 4 per cent. In the raw state it has a tensile strength of 102 pounds per square inch and of 218 pounds when burned. The absorption of the burned brickettes, made from different layers and burned to different degrees of hard- ness, varies from 5 to 16.41 per cent. The average per cent of absorp- tion for 7 brickettes was 13.06 per cent. LOWNDES COUNTY. GEOLOGY. The subsurface of Lowndes County is formed of Cretaceous strata belonging to the Tuscaloosa, the Eutaw and the Selma divisions. The mantle rock formations are the Lafayette, the Columbia and the residual Selma. Excellent outcrops of the Eutaw are found in the bluffs of the Tombigbee River. CLAY INDUSTRY. Columbus . — The Columbus Brick Manufacturing Company, oper- ated by Puckett and Lindamood,was established at Columbus in 1900. 206 CLAYS OF MISSISSIPPI. This company operates two plants at Columbus. Both are located upon the second bottom of the Tombigbee River. The clay in the first pit is about 12 feet thick and rests upon sand and gravel. The upper portion is a yellow loam. The lower clay is blue in color, and near the bottom contains some limestone and pebbles. The clay in the second pit has a yellowish brown layer at the top, then a body of blue and yellow clay with a blue clay at the bottom. The last rests upon a bed of sand. Both common and repressed brick are manufactured. The brick are molded in a stiff -mud end-cut machine. They are dried in open sheds and in steam dryers. The brick are burned in rectangular up-draft kilns of the clamp type. The Tombigbee second bottom clays furnish the best clays for the manufacture of brick in Lowndes County. They are probably Columbia in age. They rest upon sand and gravels belonging to the Lafayette MADISON COUNTY. GEOLOGY. The Vicksburg and Jackson formations of the Tertiary are the sub- formations of Madison County. The surficial deposits belong to the Lafayette and the Columbia (brown loam phase). The last named formation furnishes the brick material of the county as far as the present development of that industry is concerned. CLAY INDUSTRY. Canton . — The Canton Brick Mfg. Company at Canton operates a plant near the Illinois Central Railroad north of the station. Three kinds of clay are exposed in the pit ; which exhibits the following stratigraphy : Section of Clay Pit at Canton. Feet 5. Soil 1 4. Brownish loam 4 3. Yellow clay 3 2. Red joint clay 3 1. Blue and yellow clay The clay from No. 1 is residual Jackson. The clay from Nos. 2 and 3 belong to the Lafayette, and that from No. 4 is Columbia. ^The lowest clay is very plastic and has a high|shrinkage, so that it cannot be used alone. It is either mixed* with the clay above it Plate XXXIII. ALLISON CLAY PIT, HOLLY SPRINGS. CLAYS OP NORTHERN MISSISSIPPI. 207 or with 10 per cent crushed cinders. The cinders facilitate drying and shorten the time of burning by about 24 hours. The clay from No. 4 has a total shrinkage of 5 per cent. Its tensile strength in the raw state is 140 pounds per square inch. When burned it exhibits a strength of 316 pounds per square inch. It requires 16 per cent of water to render it plastic. It loses 20 per cent in weight in drying and burning. Its absorption is 8.33 per cent. TABLE 74, ANALYSES OF CLAYS, CANTON. No. 87 Moisture (H 2 O) 2.87 Volatile matter (CO 2 ) 3.63 Silicon dioxide (SiOa) 79.28 Iron oxide (Fe 20 j) 4.12 Aluminum oxide (AI 2 O 3 ) 4.28 Calcium oxide (CaO) .82 Magnesium oxide (MgO) .36 Sulphur trioxide (SO 3 ) -42 No. 88 2.70 3.10 73.22 5.77 9.58 2.35 .18 .40 No. 89 4.67 1.95 73.00 5.47 9.53 3.32 .27 .70 Total 95.98 97.30 98.91 RATIONAL ANALYSIS. Clay substance 11.33 Free silica 72.43 Impurities 5.72 24.23 24.11 58.57 58.42 8.70 9.76 The clay from No. 2 of the above section is more plastic and shrinks more in drying. It is red in color and has a joint structure. It shrinks in all about 8 per cent and requires the addition of 16 per cent of water. The tensile strength of the raw clay is about 8 per cent and requires the addition of 16 per cent of water to render it plastic. The tensile strength of the raw clay is 102 pounds per square inch. When burned its tensile strength is 275 pounds. Its total loss of weight in drying and burning is 27 per cent, its absorp- tion is 8.33 per cent. MARSHALL COUNTY, GEOLOGY. The subformation of Marshall County is the Wilcox (Lagrange) division of the Tertiary. The formation consists of clays and sand. The clays contain many outcrops of white pottery clays. The mantle-rock formations are the Lafayette sands and clays and the Columbia (brown loam phase). The stratigraphic relations of these formations are presented in the record of the Holly Springs town well. 208 CLAYS OF MISSISSIPPI. Record of Holly Springs Well. Thickness Depth 10. Reddish clay (Columbia) 20 feet 20 feet 9. Red sand (Lafayette) 87 “ 107 “ 8. Sand rock (Lafayette) 1 foot 108 “ 7. Clay (Wilcox — Lagrange) 52 feet 160 “ 6. Hard sandstone (Wilcox — Lagrange) .5 foot 160.5“ 5. Clay and sandstone (Wilcox — La- grange) 139.5 feet 300 “ 4. Fine water bearing sand (Wilcox — Lagrange) 40 “ 340 “ 3. Pipe clay (Wilcox — Lagrange) 13 “ 353 “ 2. Coarse sand (Wilcox — Lagrange) 4 “ 357 “ 1. Sticky clay (Porter’s Creek?) 43 “ 400 “ All layers between No. 8 and No. 1 doubtless belong to the Wilcox (Lagrange). No. 1 may be Porter’s Creek (Flatwoods). CLAY INDUSTRY. Holly Springs . — The white clays from the Wilcox are being used at Holly Springs in the manufacture of stoneware. Two potteries are operated in this place, one by the Holly Springs Stoneware Com- pany and the other by the Allison Stoneware Company. Both manufacture a general line of stoneware and both manufacture the fire brick used in their own kilns. These brick are manufactured from clays found near Holly Springs. A highly silicious clay is mixed with the white plastic clays which are used in the manufacture of stoneware. The chemical composition of the former is given below. (Bulletin No. 3, A. and M. College, 1905.) TABLE 75. ANALYSIS OF FIRE CLAY, HOLLY SPRINGS. No. 25 a Moisture (H 2 O) .87 Volatile matter (CO 2 etc.) 1.93 Silicon dioxide (Si02) 88.52 Ferric oxide (Fe20j) 1.64 Aluminum oxide (ALOj) 5.26 Calcium oxide (CaO) .73 Magnesium oxide (MgO) .13 Sulphur trioxide (SO 3 ) .43 Total 99.51 RATIONAL ANALYSIS. Clay base 13.33 Free silica 80.45 Fluxing impurities 2.50 Plate XXXIV. A. TYPICAL EROSION IN COLUMBIA LOAM, HOLLY SPRINGS. B. LAFAYETTE OVERLYING WILCOX, HOLLY SPRINGS. CLAYS OP NORTHERN MISSISSIPPI. 209 The fire brick manufactured from above mentioned clay have been used for about 25 years in some of the kilns without removal. The clay bums to a slightly pink color which disappears before vitri- fication, leaving the brick white or light cream in color. The sand grains in the clay are large. Some grains are as large as grains of wheat and of a clear, transparent, quartz variety. The stoneware clays used by the Holly Springs potteries have the following chemical properties: TABLE 76. ANALYSES OF STONEWARE CLAYS, HOLLY SPRINGS. Moisture (H 2 O) Volatile matter (CO* etc.) Silicon dioxide (Si02) .... Iron oxide (Fe20j) Aluminum oxide (Fe20j) . Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SOj) . . . , No. 20 a No. 19 a 1.51 .94 8.07 6.64 61.69 67.70 2.04 3.04 24.91 19.69 .34 1.06 .83 .58 .20 .19 Total 99.59 99.84 RATIONAL ANALYSIS. Clay base 63.13 49.90 Free silica 23.47 37.49 Fluxing impurities 3.21 4.68 No. 20a is from the Allison clay pit, and No. 19a is from the Holly Springs Stoneware Company’s pit. These pits are only a few rods apart and are located about 1J miles east of Holly Springs. The Holly Springs Brick Mfg. Company (Erby Bros.) uses the brown loam clay in the manufacture of brick by the soft-mud process. The brick are molded by hand, dried in the open air and burned in a rectangular up-draft kiln. The clay varies in compo- sition from a sandy loam at the top to a plastic joint clay in the bot- tom of the pit. The thickness of the deposit is 5 to 6 feet. A sample of clay taken from near the bottom of the pit was analyzed with the following results: 210 CLAYS OF MISSISSIPPI. TABLE 77. ANALYSIS OF BRICK CLAY, HOLLY SPRINGS. Moisture (HaO) 1.08 Volatile matter (CO 2 etc.) 2.11 Silicon dioxide (SiOj) 80.76 Iron oxide (FejOs) 4.50 Aluminum oxide (A^Oj) 8.50 Calcium oxide (CaO) 1.50 Magnesium oxide (MgO) .45 Sulphur trioxide (SO 3 ) .04 Total 98.94 RATIONAL ANALYSIS. Clay substance 21.50 Free silica 70.67 Impurities 6.49 The amount of water which the above mentioned clay requires for plasticity is 19 per cent. It has a total shrinkage of 3 per cent. The raw brickettes have a tensile strength of 42 pounds, and when soft burned the strength is 45 pounds per square inch. The loss of weight in water-smoking and burning is 16 per cent. MONTGOMERY COUNTY. GEOLOGY. The subformations of Montgomery County are the Wilcox (La- grange) and the Tallahatta buhrstone (Silicious Claiborne). The surface formations belong to the Lafayette and the brown loam phase of the Columbia, which is widely distributed over the county. CLAY INDUSTRY. Winona . — The Columbia formation is used at Winona in the man- ufacture of brick. The Jessty Brick and Lumber Company manu- factures brick by the dry-press process. They use a mixture of brown loam clay and a white clay from the Lafayette. The clay pit from which the white clay is taken is from an outcrop on the Southern Railroad about 1 mile west of town. It bums white and leaves white specks on the surface of the brick, presenting an attractive appearance. It also reduces the shrinkage of the brown clay and raises its fusion point. The brown loam clays and the Wilcox clays are the sources of the principal brick material of this county. CLAYS OF NORTHERN MISSISSIPPI. 211 MONROE COUNTY. GEOLOGY. The substrata of Monroe County belong to the Tuscaloosa, the Eutaw (Tombigbee), and' the Selma. The surficial formations are the Lafayette sands and clays and the Columbia loams. The second bottom of the Tombigbee River, which crosses the county from north to south, is made up of sand and gravel, overlying which is a bed of clay grading into a loam at the top. The river has cut its trench into the soft rock of the Eutaw, and for the greater part of its distance marks the boundary between the Eutaw and the Selma; the higher Eutaw bluff on the west side of the stream being capped with the Selma. When not removed by erosion these higher bluffs are mantled with Lafayette and Columbia. CLAY INDUSTRY. Aberdeen . — At Aberdeen, just south of the waterworks, the La- fayette rests upon the eroded surface of the Eutaw. The line of contact is quite clearly marked in this instance by a thin layer of friable, whitish sandstone. The section exposed is as follows: Section at Aberdeen. Feet 2. Orange colored sand with some clay lenses, crossbedded with some joint clay at the top 12 1. Greenish sand (Eutaw) 20 At a lower horizon, on the river bank south of the bridge, about 30 feet of bluish gray sand containing some clay is exposed. In places the sand contains fossils and micaceous concretions containing iron pyrites. There are also some sandstone concretions, and in one exposure a rather persistent layer of friable sandstone from 1 to 2 feet in thickness. The clay pit belonging to the Aberdeen Sand- Lime Brick Company is located on the second bottom of the Tom- bigbee River. The clay is not being used at the present time, as the company is engaged in the manufacture of sand-lime brick. The old clay pit exhibits the following section: Old Clay Pit at Aberdeen. Feet 3. Sandy loam soil 1 2. Joint clay, blue in places 7 1. Sand 212 CLAYS OF MISSISSIPPI. The clay from No. 2 has a tensile strength in the raw state of 87 pounds per square inch. It has a total shrinkage of 10 per cent and loses 11 per cent in weight in being water-smoked and burned. When mixed with 10 per cent coal the clay has a total shrinkage of 6 per cent and requires 17 per cent of water to render it plastic. Raw, it has a tensile strength of 140 pounds per square inch, and burned the strength is 263 pounds per square inch. Loss of weight in burning is 10 per cent. The burned brickettes have an absorption of 12.24 per cent. When mixed with 10 per cent of cinders its shrinkage is 6 per cent. In the raw state its strength is 175 pounds; burned, 300 pounds. A sample of the clay has the following chemical compo- sition : TABLE 78. ANALYSIS OF JOINT CLAY, ABERDEEN. No. 103 Moisture (H*0) 4.95 Volatile matter (CO» etc.) 4.92 Silicon dioxide (SiO*) 71.13 Iron oxide (FejOj) 7.75 Aluminum oxide (A1 2 Oj) 9.12 Calcium oxide (CaO) .42 Magnesium oxide (MgO) .63 Sulphur trioxide (SO 3 ) .08 Total 99.00 RATIONAL ANALYSIS. Clay substance 23.07 Free silica 60.41 Impurities 8.88 Amory . — At Amory the Tombigbee second bottom clay is used by two companies in the manufacture of brick. The stratigraphy of the formation at this point is shown by the following well record: General Section of Amory Wells. Thickness Depth Surface loam and clay (Columbia ?) . . . 15 feet Gravel, water-bearing (Lafayette?). . . . . . 25 “ 40 “ Blue sand (Eutaw) ... 100 “ 140 “ Sand, water-bearing (Eutaw) . . . 50 “ 190 “ CLAYS OF NORTHERN MISSISSIPPI. 213 The L. H. Tubbs Brick Manufacturing Company began the manu- facture of brie 1 ; at Amory in 1894. They use a stiff-mud machine of the plunge; type. Section of Clay Pit, Amory. Feet 4. Sandy soil 1 3. Yellowish loam 3 2. Joint clay, bluish and reddish tints 7 1. Sand and gravel 5 There is no distinct line of separation between 2 and 3. The clay of No. 2 requires 14 per cent of water for plasticity. It has a total shrinkage of 6 per cent. Its tensile strength, raw, is 100 pounds per square inch, and burned, it has a strength of 220 pounds. It absorbs 11.86 per cent of water in the soft burned stages. Mixed with 10 per cent of coal its physical properties are: Total shrinkage, 6§ per cent; tensile strength, raw, 150 pounds; burned, 273 pounds. Mixed with 10 per cent of cinders, its physical properties are: Shrink- age, 5 per cent; tensile strength, raw, 155 pounds; burned, 300 pounds per square inch. The chemical composition of a sample of No. 3 is given below: TABLE 79. ANALYSIS OF YELLOW LOAM CLAY, AMORY. No. 94 Moisture (H 2 O) 5.20 Volatile matter (CO 2 etc.) 5.10 Silicon dioxide (Si02) 71.04 Iron oxide (Fe 203 ) 7.92 Aluminum oxide (AI 2 O 3 ) 9.27 Calcium oxide (CaO) .87 Magnesium oxide (MgO) .31 Sulphur trioxide (SO3) trace Total 99.71 RATIONAL ANALYSIS. Clay substance 23.45 Free silica 56.86 Fluxing impurities 9.10 Mr. C. C. Camp has operated a brick plant at Amory since 1896. In 1904 he installed new machinery. The clay is molded in a stiff- mud machine of the auger type. The die is a double bar die. The 214 CLAYS OF MISSISSIPPI. cutter is an automatic end-cut machine. The clay pit is near that of the other yard, and the stratigraphic conditions are similar. The brick are burned in rectangular up-draft kilns. NEWTON COUNTY. GEOLOGY. The southwestern comer of Newton County is underlain by the Jackson formation. The remainder of the county is underlain by the Claiborne. The mantle rocks belong to the Lafayette and the Columbia and residual clays form the bed-rock formations. CLAY INDUSTRY. Newton . — The surface formations are used in the manufacture of brick at Newton. The Hancock Brick Company operates a plant South of the Alabama and Vicksburg Railroad, west of town. The brick are dried under a large shed open at both ends. They are burned in rectangular up-draft kilns. Tjie clay is reddish with a yellow loam overlying it. The absorption of the clay in the bottom layer is 9.52 per cent, and the absorption of that in the top layer is 13.79 per cent. In a railroad cut on the Mobile, Jackson and Kansas City Railroad, south of town, there is an exposure of the following formations: Section of Surface Formations at Newton. Feet 3. Yellow loam with some pebbles 6-8 2. Orange sand with silicious pebbles 6-10 1 . Red sand with white clay partings 6-8 No. 1 contains partings of clay and has an irregular stratification. In some places the partings are in the nature of very fine white lines, as though they had been drawn by the painter’s brush or a grainer. The top of this layer is somewhat conglomerate, small masses of clay being mixed with the sand. The pebbles of No. 2 are more numerous at the top. No. 3 appears to be a weathered product of No. 2. If Nos. 1 and 2 are Lafayette, as seems probable, then No. 3 doubtless represents the Columbia. Plate XXXV, A. CLAY PARTINGS IN LAFAYETTE SANDS, NEWTON. B. EROSION IN LAFAYETTE SANDS BY UNDERGROUND WATER, NEWTON CLAYS OF NORTHERN MISSISSIPPI. 215 TABLE 80. ANALYSES OF CLAYS, NEWTON. No. 91 Moisture (H 2 O) 1.52 Volatile matter (CO 2 etc.) 3.08 Silicon dioxide (Si 02 ) 84.54 Iron oxide (Fe 20 a) 4.12 Aluminum oxide (AI 2 O 3 ) .60 Calcium oxide (CaO) 5.83 Magnesium oxide (MgO) .22 Sulphur trioxide (SO 3 ) .23 No. 92 2.32 3.20 82.82 3.75 7.05 .50 .17 .00 Total 100.14 99.41 RATIONAL ANALYSIS. Clay substance Free silica Impurities 1.50 17.83 83.63 71.54 10.40 4.42 No. 91 is from the Hancock pit; No. 92 is from ah outcrop \ mile west. The physical properties of No. 91 are: Water required for plasticity, 20 per cent; total shrinkage, 10 per cent; tensile strength of raw clay, 87 pounds per square inch; burned, 150 pounds per square inch. No. 92 has the following physical properties: Total shrinkage, 1 per cent; water required for plasticity, 17 per cent; tensile strength, raw, 37 pounds; burned, 53 pounds per square inch. It is deficient in bonding matter. NOXUBEE COUNTY. GEOLOGY. The subsurface of Noxubee County is the Selma and the Ripley divisions of the Cretaceous, and the Wilcox. The surficial formations are isolated outcrops of the Lafayette, the Columbia and the residual Selma clays. CLAY INDUSTRY. Macon . — The surface clays are used at Macon by the Cline Brick Manufacturing Company in the manufacture of brick by the soft- mud process. The clay is tempered in a ring pit. The brick are molded by hand and burned in rectangular up-draft kilns. In the clay pit, about 8 feet of clay rests upon the Selma chalk. The clay in the upper portion of the bed is red in color and of a coarse, sandy texture. It is probably Lafayette. The lower portion of the clay is 216 CLAYS OF MISSISSIPPI. more plastic and cannot be used alone on account of sticking in molds in molding, and of checking and cracking in drying. The Selma chalk contains concretions of iron pyrites which, upon exposure to the atmosphere, oxidize producing ferrous sulphate and sulphuric acid which act upon the limestone. The limestone being dissolved, the insoluble clay which it contains is left behind, and accumulates to form a thick bed. The clay immediately overlying the limestone is greenish in color, a condition probably due to the presence of ferrous sulphate. Concretions of iron oxide also occur along the line of contact between the clay and the limestone. These are formed by the oxidation of the iron pyrites nodules. The following analyses are of two samples of the Selma chalk from Macon: TABLE 81. ANALYSES OF SELMA LIMESTONES No. 100, MACON. Moisture (H 2 0) Volatile matter (C0 2 etc.) Silicon dioxide (Si0 2 ) Aluminum oxide (AI2O3) . Iron oxide (Fe 2 03 ) Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SO 3 ) Total No. 1 No. 2 1.25 .95 36.28 35.15 9.18 13.03 .00 5.25 3.50 2.18 45.92 41.56 .84 .36 .34 .64 97.31 99.12 No. 2 was collected by A. F. Crider from Macon Bluff on the Tombigbee River. The greenish colored clay overlying the limestone has the follow- ing chemical constituents: TABLE 82, ANALYSIS OF RESIDUAL SELMA CLAY, MACON. No. 101 Moisture (H 2 0) 11.60 Volatile matter (C0 2 etc.) 10.00 Silicon dioxide (Si0 2 ) 50.51 Aluminum oxide (Al 2 Os) 17.31 Iron oxide (Fe 2 Os) 5.75 Calcium oxide (CaO) 2.70 Magnesium oxide (MgO) 1.40 Sulphur trioxide (SOj) .21 Total, 99.48 RATIONAL ANALYSIS. Clay substance 43.79 Free silica 30.16 Impurities 10.06 Plate XXXVI. A. RESIDUAL CLAY AND LAFAYETTE OVERLYING SELMA CHALK, MACON. B. SELMA CHALK ON NOXUBEE RIVER, MACON. CLAYS OF NORTHERN MISSISSIPPI. 217 There is but little doubt that the above mentioned clay has been derived from the Selma limestone, the decomposition of which was influenced by the decomposition of the iron pyrites present in the limestone. This bottom clay is too fat to be used in the manufacture of brick. It sticks to the molds when used in the soft -mud machine and cracks in drying when used in the stiff -mud machine. The La- fayette clay lying above the residual Selma is much leaner and con- tains a high per cent of iron. The chemical analysis of the Lafayette clay from Macon follows: TABLE 83. ANALYSIS OF CLAY, MACON. No. 77 Moisture (H 2 0) 7.59 Volatile matter (C0 2 etc.) 7.75 Silicon dioxide (Si0 2 ) 57.25 Iron oxide (Fe 2 Oa) 18.95 Aluminum oxide (A1 2 Os) 6.17 Calcium oxide (CaO) 1.05 Magnesium oxide (MgO) .95 Sulphur trioxide (SO 3 ) .21 Total 99.92 RATIONAL ANALYSIS. Clay substance 15.61 Free silica 50.00 Impurities " 27.16 In the manufacture of brick the best results are to be obtained by mixing the Lafayette clay with the Selma residual clay. Near the railroad station at Macon there is a residual clay which is probably derived from the Flatwoods clay. The grain of the clay is fine and it has shrinkage of 15 per cent. The tensile strength of the raw clay is 87 pounds ; the burned clay has a strength of 78 pounds ; the water required for plasticity is 18 per cent; the amount of absorption of the burned clay is 8.69 per cent. The absorption of the Lafayette clay is 11.42 per cent. 218 CLAYS OF MISSISSIPPI. OKTIBBEHA COUNTY. GEOLOGY. The bed-rock formations of Oktibbeha County belong to the Cretaceous and the Tertiary periods. The Selma chalk and a few outliers of the Ripley are present in the eastern part of the county. The western part of the county is underlain by the Wilcox-Eocene. The mantle deposits are Lafayette, residual Selma and Columbia. The last two are well represented in the. western part of the county, but only by isolated outcrops in the eastern half. The residual Selma clay and the Columbia are used in the manufacture of brick in Starkville. CLAY INDUSTRY. Starkville . — At Starkville the Howard Brick Manufacturing Com- pany uses a clay which rests directly upon the surface of the Selma chalk. The greater part of the clay deposit was formed doubtless by the decomposition of the limestone. The limestone immediately below the clay is partly decomposed and contains 19.30 per cent of clay. The following analyses show the composition of the lime- stone and the clay immediately above: TABLE 84. ANALYSES OF LIMESTONE AND CLAY, STARKVILLE. Moisture (H 2 0) Volatile matter (C0 2 etc.) Silicon dioxide (Si0 2 ) Iron oxide (Fe 2 Oa) Aluminum oxide (AI 2 O 3 ) . Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (S0 2 ) . . . No. 40 No. 41 .85 4.75 23.15 2.27 20.60 65.30 4.62 12.18 7.63 12.63 41.81 1.50 .81 .63 .25 .25 Total 99.72 99.51 RATIONAL ANALYSIS. Clay substance 19.30 31.95 Free silica 11.73 51.45 Impurities 47.49 14.18 No. 40 — Selma limestone. No. 41 — Residual Selma clay. Samples of clay and limestone taken from another part of the pit have the following composition: CLAYS OF NORTHERN MISSISSIPPI. 219 TABLE 85. ANALYSES OF SELMA LIMESTONE AND OVERLYING CLAY, STARK- VILLE - No. 9 No. 10 Moisture (H 2 0) 75 .55 Volatile matter (CO 2 ) 28.20 .97 Silicon dioxide (Si 02 ) 17.03 76.60 Iron oxide (Fe 203 ) 3.33 2.00 Aluminum oxide (AI 2 O 3 ) 21.00 18.37 Calcium oxide (CaO) 29.29 .90 Magnesium oxide (MgO) .00 .00 Sulphur trioxide (SO 3 ) .72 .70 Potassium oxide (K 2 0) .00 .00 Sodium oxide (Na 2 0) .00 .00 Total 100.32 100.09 RATIONAL ANALYSIS. Clay substance 53.13 46.47 Free silica 7.66 55.00 Impurities 33.34 3.60 No. 9 — Selma limestone. No. 10 — Residual Selma clay. The sample of limestone was taken from immediately below the clay. It contains 53.13 per cent of clay substance, or is more than half clay. The clay sample was from near the bottom of the clay deposit. The bottom clay is usually too plastic, and has too high a shrinkage to be used alone in the manufacture of brick. The proper texture and shrinkage is obtained by mixing the more sandy top clay with the bottom clay. The top clay contains considerable non-plastic material. The clay immediately overlying the limestone requires careful selection to prevent defects in the brick, because it contains in places nodules or concretions of limestone and ironstone. These nodules are liable to break the wires of the cutter, and to produce cavities or fused masses in the brick. The limestone nodules represent the more insoluble portions of the chalk, such as the casts of shells and the concretions of which fossils form the nuclei. The iron nodules were formed doubtless by the oxidation of concretionary nodules of iron pyrites, which are not of uncommon occurrence in the chalk. The oxidation of the pyrite produces sulphuric acid, which attacks the calcium carbonate, forming calcium sulphate (gypsum), which is soluble in water and thus may be dissolved out as the clay weathers. The chemical reaction is as follows:* FeS 2 + 60=FeSO 4 -fSO 2 or FeS 2 + 30 = H 2 0 + FeS0 4 + H 2 S ♦Van Hise, Metamorphism, p. 214. 220 CLAYS OF MISSISSIPPI. The iron sulphate (FeS0 4 ) may be changed to iron oxide, limonite, by oxidation and hydration: FeS0 4 + 20 + 7H 2 0 = 2Fe 2 0 3 + 3H 2 0 + 4H 2 S0 4 The sulphuric acid (H 2 S0 4 ) then reacts with the calcium carbonate to produce calcium sulphate : CaC0 3 + H 2 S0 4 = CaS0 4 + H 2 0 + C0 2 or the iron sulphate may react directly in the following manner: FeS0 4 CaC0 3 = CaS0 4 + FeCOg The sulphuric acid, together with the action of the acids produced by decaying vegetation, dissolve out the limestone and cause the accumulation of the insoluble clay residue. Agricultural and Mechanical College . — The residual Selma clay also occurs on the campus of the State Agricultural and Mechanical College. From an excavation made during the construction of the steam pipe tunnel, the following samples were taken from a point immediately in front of the Mess Hall. The analyses of these samples are recorded below : TABLE 86. ANALYSES OF LIMESTONE AND CLAYS, AGRICULTURAL COLLEGE. No. 64 No. 65 No. 66 No. 67 No. 68 No. 69 Moisture (H 2 O) 1.50 6.02 5.50 5.00 4.46 5.36 Volatile matter (C0 2 ) 24.50 6.50 5.00 4.35 5.65 2.78 Silicon dioxide (Si0 2 ) 29.98 63.35 67.60 69.35 66.85 66.51 Aluminum oxide (Al 2 Os) 5.60 13.70 12.55 12.65 12.05 15.10 Iron oxide (Fe 2 03 ) 5.45 7.90 7.60 6.80 7.07 7.00 Calcium oxide (CaO) 31.62 .80 .80 .50 1.62 1.00 Magnesium oxide (MgO) .14 .60 .78 .58 .18 .58 Sulphur trioxide (SO 3 ) .21 .34 .17 .42 .08 .31 Total 99.00 99.21 100.00 99.65 97.96 98.64 RATIONAL ANALYSIS. Clay substance 14.16 34.66 31.75 32.00 30.48 38.20 Free silica 23.40 47.24 43.85 54.48 48.42 48.76 Impurities 37.42 9.64 9.35 8.30 8.95 8.89 No. 64 is the limestone or chalk immediately underlying the clay. Nos. 65 to 69, inclusive, are samples of clay from the tunnel taken in order from bottom to top of the first 5 feet of clay, one sample being taken from each successive foot. The absorption of No. 64 is 18 per cent. Clay No. 65 has a total shrinkage of 8 per cent; it requires 16 per cent of water for plasticity; it has a tensile strength, raw, of 133 pounds per square inch, and when burned has a strength of 146 CLAYS OP NORTHERN MISSISSIPPI. 221 pounds per square inch. It loses 12 per cent in weight in being burned, and has an absorption of 7.27 per cent. When mixed with 10 per cent of coal it requires 14 per cent of water to render it plastic. The loss of weight in the soft -burned brickettes is 15 per cent. It has a total shrinkage of 3J per cent. The tensile strength of the raw clay is 119 pounds per square inch. When burned it has a strength of 150 pounds per square inch. Its absorption is 12.24 per cent. When mixed with 10 per cent of cinders the clay has a total shrinkage of 3J per cent; requires 15 per cent of water for plasticity; has a tensile strength, raw, of 72 pounds per square inch, and when burned a strength of 153 pounds per square inch. Its loss of weight in burning is 14 per cent. Its absorption is 12.9 per cent. Clay No. 66 has a total shrinkage of 6 per cent. It requires 15 per cent of water for plasticity. The loss in burning is 12 per cent. The tensile strength of the raw clay is 94 pounds per square inch. When burned it has a strength of 250 pounds per square inch. Its absorption is 9.8 per cent. Clay No. 67 has a total shrinkage of 5J per cent. It requires 14 per cent of water for plasticity. The loss of weight in burning is 14 per cent. The raw clay has a tensile strength of 94 pounds per square inch and when burned its strength is 240 pounds per square inch. Its absorption is 9.4 per cent. When mixed with 10 per cent of coal the clay requires 16 per cent of water; shrinks 3J per cent; has a tensile strength, raw, of 77 pounds and soft -burned of 106 pounds per square inch. When mixed with 10 per cent of cinders it requires 14 per cent of water; has a total shrinkage of 3J per cent. The raw clay has a strength of 66 pounds and the burned clay a strength of 131 pounds per square inch. Its absorption is 15.09 per cent. Clay No. 68 requires 16 per cent of water; it has a total shrinkage of 5 per cent; its loss of weight in burning is 13 per cent; its tensile strength, raw, is 133 pounds per square inch. When burned it has a strength of 312 pounds per square inch. Its absorption is 9.61 per cent. Clay No. 69 requires 17 per cent of water for plasticity. The total shrinkage of the clay is 5 per cent. The tensile strength of the raw clay is 105 pounds per square inch. The strength of the burned clay is 333 pounds per square inch. Its absorption is 13.55 per cent. The average absorption of all except No. 64 is 10.12 per cent. 222 CLAYS OP MISSISSIPPI. In an excavation for a sewer line a few rods south of the above mentioned tunnel, a bed of clay was exposed resting upon the surface of the chalk. A sample of the chalk and one sample from the bottom and one sample from the middle of the clay deposit were taken and analyzed with the following results: TABLE 87. ANALYSES OF LIMESTONE AND CLAYS, AGRICULTURAL COLLEGE. Moisture (H 2 0) No. 35 81 No. 36 4.06 No. 37 2.95 Volatile matter (C0 2 etc.) 28.61 8.60 10.90 Silica (Si0 2 ) 27.05 60.43 56.97 Iron oxide (Fe 2 Oj) 5.45 10.05 10.40 Aluminum oxide (AUO 3 ) . , 6.45 13.15 15.09 Calcium oxide (CaO) 30.21 2.13 1.00 Magnesium oxide (MgO) . . 00 .54 1.25 Sulphur trioxide (SO 3 ) 32 .36 .34 Total 98.90 99.32 98.90 Clay substance RATIONAL ANALYSIS. 16.31 33.26 38.17 Free silica 20.47 45.97 39.23 Impurities 35.93 12.08 12.99 No. 35 — Selma chalk. Nos. 36 and 37 — Residual Selma clays. Maben . — The Maben Brick Manufacturing Company, of Maben, began the manufacture of brick in 1905. Two kinds of clay are used. One kind is a white clay from the B. F. Sanders farm, a few miles west of Maben. The clay belongs to the Wilcox (Lagrange) division of the Lignitic. It remains white when burned. Its shrinkage is very low. The chemical composition of a sample is given below: TABLE 88. ANALYSIS OF WHITE CLAY, MABEN. No. 59 a Moisture (H 2 0) 1.47 Volatile matter (C0 2 etc.) 9.24 Silica (Si0 2 ) 59.82 Iron oxide (Fe 2 Os) 1.26 Aluminum oxide (Al 2 Os) ' 27.19 Calcium oxide (CaO) .49 Magnesium oxide (MgO) .37 Sulphur trioxide (SO 3 ) .31 Total 100.15 RATIONAL ANALYSIS. Clay substance 68.80 Free silica 18.21 Impurities 2.43 CLAYS OF NORTHERN MISSISSIPPI. 223 The above mentioned plant also uses a surface clay belonging to the yellow loam phase of the Columbia. The clay pit has the follow- ing stratigraphy: Section of Clay Pit , Maben. Feet 2. Sandy loam, gray to yellow 2 1. Clay, gray in color 6 In the bottom of the pit there are numerous ironstone concretions. The brick burned from the surface clay vary in color from bright red to chocolate. They are molded in a stiff-mud machine of the auger type. The clay is prepared in a granulator and disintegrator and tempered in a horizontal pug mill. The brick are burned in rectangular up-draft clamp kilns. The brick are dried by being packed on pallets and placed on racks in covered sheds. PANOLA COUNTY. GEOLOGY. The Wilcox forms the subsurface of Panola County. The mantle rocks consist of the alluvial deposits of the Yazoo basin, the Loess, the Lafayette and the Columbia. The clay from the last named formation is used in the manufacture of brick. CLAY INDUSTRY. Sardis . — At Sardis the clay from the Columbia is employed in the manufacture of brick by the Buchanan Brick Manufacturing Com- pany. The brick are molded by the soft-mud process. The clay is prepared in a disintegrator and tempered in a pug mill. It is then molded in a soft-mud machine which is operated by steam power. The brick are burned in rectangular up-draft kilns. The clay in the pit has a thickness of 8 to 10 feet. The upper portion is much leaner than the basal portion. The following analysis gives the composition of the latter: 224 CLAYS OF MISSISSIPPI. TABLE 89. ANALYSIS OF COLUMBIA CLAY, SARDIS. No. 80 Moisture (H 2 0) 2.90 Volatile matter (C0 2 etc.) 2.42 Silicon dioxide (Si0 2 ) 74.41 Iron oxide (Fe 2 Os) 5.37 Aluminum oxide (AI2O3) 12.22 Calcium oxide (CaO) 1.40 Magnesium oxide (MgO) 1.25 Sulphur trioxide (SO3) .03 Total 100.00 RATIONAL ANALYSIS. Clay substance 30.91 Free silica 60.04 Impurities 8.05 The physical properties of the Sardis clay are as follows: The clay requires 18 per cent of water to render it plastic. It has a total shrinkage of 6 per cent. The raw brickettes show a tensile strength of 111 pounds per square inch, and when burned they have a strength of 140 pounds per square inch. The loss in burning is 5 per cent of the weight and the absorbtive power of the burned clay is 14.51 per cent. The minimum amount of bonding power is exhibited by the clay from the upper portion of the pit. The basal clay requires the addition of non-plastic material for the manufacture of soft-mud brick. Batesville . — No brick are being manufactured at Batesville at present. No doubt the Brown loam clays which are well represented there could be utilized with the same degree of success that has been attained in other parts of the county. The unweathered Loess which lies at the base of the Columbia cannot be used alone in the manufacture of brick. It lacks bonding power. The following analy- sis is of a sample of unweathered, or but slightly^ weathered, ’Loess from Batesville. TABLE 90. ANALYSIS OF UNWEATHERED LOESS, BATESVILLE. No. 78 Moisture (H 2 0) 1.81 Volatile matter (C0 2 ) 3.20 Silicon dioxide (Si0 2 ) 75.11 Iron oxide (Fe 2 Os) v 5.50 Aluminum oxide (A 1 2 Oj) 10.70 Calcium oxide (CaO) .60 Magnesium oxide (MgO) .47 Sulphur trioxide (S0 2 ) .00 Total 97.39 CLAYS OF NORTHERN MISSISSIPPI. 225 RATIONAL ANALYSIS. Clay substance 27.07 Free silica 62.53 Impurities 6.57 The aluminum in analysis No. 78 is probably largely contained in undecomposed feldspars. This fact undoubtedly accounts for the low bonding power of the clay. The best residual clays from this formation are to be found in areas where the Loess has not been sub- jected to rapid erosion. Second bottom deposits usually afford the best clays. The physical properties of the above mentioned Loess clay are as follows: It requires 18 per cent of water for plasticity. The air shrinkage is 4 per cent. The raw clay has a maximum tensile strength of 72 pounds per square inch, and the hard-burned brickettes show a maximum strength of 111 pounds per square inch. The color of the burned clay is red. The clay cracks badly when dried rapidly and is deficient in bonding power. PONTOTOC COUNTY. GEOLOGY. Pontotoc County is crossed from north to south by the following formations, taking them in order from east to west: Selma chalk, Ripley and Wilcox. The surficial formations belong to the Lafayette and the Columbia. CLAY INDUSTRY. Pontotoc . — The Columbia clay is used at Pontotoc in the manu- facture of brick. The plant is operated by the Austin Brick Manu- facturing Company. The following is an analysis of a sample of the clay used: TABLE 91. ANALYSIS OF COLUMBIA CLAY, PONTOTOp. No. 105 Moisture (H 2 0) 2.13 Volatile matter (C0 2 etc.). v 3.70 Silicon dioxide (Si0 2 ) 77.57 Iron oxide (Fe 2 03 > 6.25 Aluminum oxide (ALO 3 ) 7.25 Calcium oxide (CaO) .50 * Magnesium oxide (MgO) 1.90 Sulphur trioxide (SO 3 ) .17 Total 99.47 7 226 CLAYS OF MISSISSIPPI. RATIONAL ANALYSIS. Clay substance 18.34 Free silica 69.05 Impurities 8.82 Clay No. 105 has an absorption of 12.96 per cent. Its total shrinkage is 6§ per cent. It requires 15 per cent of water for plas- ticity. The tensile strength of the raw clay is 60 pounds per square inch, and of the burned clay 80 pounds per square inch. PRENTISS COUNTY. GEOLOGY. The Subcarbon if erous forms the bed-rock of a small part of the southeastern portion of Prentiss County. The Tuscaloosa clays outcrop along the eastern part of the county. The central portion is occupied by the Eutaw formation, and the western portion, with the exception of the northwestern comer, by the Selma chalk. The Ripley occupies a small area west of the Selma. The mantle rock formations are the residual clays of these various bed-rocks, the Lafayette and the Columbia loams. The clays of these surface for- mations are being used in the manufacture of brick and tile at Boone- ville and at Thrasher. CLAY INDUSTRY. Booneville . — The Booneville Brick and Tile Company of Booneville use the clay from a pit in which the following stratigraphy is revealed: Section of Clay Pit at Booneville. > Feet 4. Sandy loam (Columbia) 2-3 3. Reddish clay 3-5 2. Bluish clay 4 1. White chalk containing shells A little higher up the clay has a greater thickness, as the record of Mr. H. T. Turkett’s well seems to indicate., Turkett Well Record , Booneville. Feet 1. Yellow and blue clay 20 2. Blue limestone 20 3. Water-bearing sand . 5 Plate XXXVII A. RESISTANT LAYER IN THE COLUMBIA LOAM, BRANDON. B. LAFAYETTE SANDS, BRANDON THE RED SAND OF THE OUTCROP WEATHERED WHITE IN THE FLAT BELOW. CLAYS OF NORTHERN MISSISSIPPI. 22 ? Clay No. 2 of the pit section has the maximum shrinkage when hard burned, and No. 4 the minimum shrinkage. The brick shrink about £ inch in length and £ inch in width. A mixture of these clays is used in the manufacture of brick and tile. In drying the brick, care must be exercised to prevent the currents of air from striking the brick too soon after they are brought from the machine. Too rapid drying at first causes cracking and checking. Because of the presence of lime and ironstone concretions in some parts of these clays, care must also be exercised in burning to prevent fusion in some parts of the kiln before the brick in the other parts have reached the proper hardness. The lime acts as a flux to melt the iron. This action runs the brick together in a slaggy mass. The ends of the. eye-brick are usually glazed by this reducing action of the lime. No granulator, disintegrator or pug mill is used in preparing and tempering the clay. It is molded in a stiff-mud side-cut machine. The brick and tile are burned in rectangular up-draft kilns of the clamp type. The com- pany also manufactures some drain tile each year. . Thrasher . — At Thrasher, the Thrasher Brick Manufacturing Com- pany opened a yard for the manufacture of brick in 1906. The clay used is a surface clay, probably of Columbia age. Its prevailing color is yellow. The brick are molded in a stiff-mud machine of the plunger type. They are burned in rectangular up-draft kilns. RANKIN COUNTY* GEOLOGY, The subsurface of Rankin. County is occupied by Tertiary strata belonging to the Jackson, Vicksburg and Grand Gulf groups. The surficial formations are the Lafayette and the Columbia. CLAY INDUSTRY, Brandon . — The Columbia has been used at Brandon in the manu- facture of brick by the soft-mud process. One plant was located southeast of town and another across from the Alabama and Vicksburg station, northeast of town. Neither of these plants is in operation at present. 228 CLAYS OF MISSISSIPPI. On the siope of the hill above the Alabama and Vicksburg station there is an exposure of Lafayette clay which has the following com- position : TABLE 92. ANALYSIS OF COLUMBIA CLAY, BRANDON. No. 74 Moisture (H 2 0) 4.89 Volatile matter (C0 2 etc.) 4.86 Silicon dioxide (Si0 2 ) 75.16 Iron oxide (Fe 2 Oa) 5.77 Aluminum oxide (ALO3) 7.75 Calcium oxide (CaO) .62 . Magnesium oxide (MgO) .87 Sulphur trioxide (SO3) .00 Total 99.92 RATIONAL ANALYSIS. Clay substance 19.60 Free silica 66.05 Impurities 7.26 At the foot of the hill, east of the station at Brandon, there is an outcrop of white Vicksburg limestone. South of the station at a little higher level is a marl which is highly fossiliferous. The section exposed is as follows: Section South of the Railroad Station , Brandon. Feet 4. Brownish loam 5 3. Red to purple clay 4 2. Yellow clay ' 1 1. Marl containing shells 6 Layers 2 and 3 are residual clays formed by the decomposition of the marl. In an abandoned railroad cut, at the top of the divide upon which Brandon is located, there is an outcrop of Lafayette sand capped by a layer of light brown loam. The Lafayette, in places, weathers to a white sand. The grains of sand are coarse and mostly fragments of transparent quartz crystals. Some of the grains are opaque white. About 25 feet of this sand is exposed. Farther west, the sand has partings of white clay at its base. Above the red sand there is a foot or two of lighter colored transition loam, then about one foot of hard, indurated resistant loam. So indurated is the layer that on an exposed surface it projects from the face of the exposure, and when Plate XXXVIII, B. VICKSBURG LIMESTONE. NEAR BRANDON. CLAYS OF NORTHERN MISSISSIPPI. 229 broken up forms a sort of gravel. In places it serves as a sort of capping to protect the softer underlying rocks and thus produces a variety of small tppographic forms. Above the indurated layer there is an exposure of about 4 feet of brown loam covered by a foot or more of soil. A sample of clay from the indurated portion has the following chemical composition : TABLE 93. ANALYSIS OF COLUMBIA CLAY, BRANDON. No. 75 Moisture (H 2 0) 1.56 Volatile matter (C0 2 etc.) 2.65 Silicon dioxide (Si0 2 ) 82.32 Iron oxide (Fe 2 Os.) 5.77 Aluminum oxide (Al 2 Os) v 5.17 Calcium oxide (CaO) .50 Magnesium oxide (MgO) .91 Sulphur trioxide (SO3) .09 Total 98.97 RATIONAL ANALYSIS. Clay substance '. . 13.08 Free silica 76.25 Impurities 7.27 The cementing substance in the hard layer mentioned above is undoubtedly silica. The amount of iron and of calcium carbonate does not seem adequate to form such a degree of induration. Rankin State Farm . — In an attempt to find a clay suitable for the manufacture of brick on the State farm in Rankin County the writer collected a number of samples. A chemical analysis of one of these samples was made with the following results: TABLE 94. ANALYSIS OF CLAY, RANKIN COUNTY STATE FARM. * No. 71 Moisture (H 2 0) .81 Volatile matter (C0 2 etc.) 9.20 Silicon dioxide (Si0 2 ) 81.72 Iron oxide (Fe 2 03 ) 4.81 Aluminum oxide (AUO 3 ) .86 Calcium oxide (CaO) .62 Magnesium oxide (MgO) .89 Sulphur trioxide (SO 3 ) .36 Total 99.27 RATIONAL ANALYSIS. Clay substance 2.17 Free silica 80.71 Impurities 6.58 230 CLAYS OF MISSISSIPPI. The absorption of clay No. 71 is 14.94 per cent. It contained such a small amount of clay substance that it was deficient in bonding power. It is about four-fifths sand and contains more than 6 per cent of fluxing impurities. SCOTT COUNTY. GEOLOGY. The substrata of Scott County belong to the Claiborne, Jackson and Vicksburg. The Lafayette and Columbia form the surficial for- mations. There are also some .residual clays formed from the Jackson marls. CLAY INDUSTRY. Forest . — At Forest, a residual Jackson clay outcrops in a small ravine in the western part of the town. The analysis of this clay is given in No. 113, below: TABLE 95. ANALYSES OF CLAYS, FOREST No. 113 No. 112 Moisture (H 2 0) Volatile matter (C0 2 etc.) Silicon dioxide (Si0 2 ) Iron oxide (Fe 2 Os) Aluminum oxide (ALO 3 ) . Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SO3) . . . . 5.05 1.80 6.41 2.48 69.01 86.38 8.02 2.82 5.60 1.23 2.50 4.17 .48 .27 .51 .02 Total 98.58 99.17 RATIONAL ANALYSIS. Clay substance Free silica Impurities 20.29 3.11 56.74 84.50 10.19 7.28 A sample of clay taken from a railroad cut near the station belongs to a surface loam. The deposit contains some pebbles at the base and the clay has some small gravels. It is probably Lafayette or Columbia. The composition of a sample is given in No. 112 of the above table. The burned brickettes have an absorption of 9.02 per cent. Plate XXXIX. B. LOCAL FAULT IN THE JACKSON STRATA, MORTON. CLAYS OF NORTHERN MISSISSIPPI. 231 Morton . — In the southern part of the town of Morton there is an outcrop of Jackson which has the following stratigraphy (see Plate XXXIX, A): Section of the Jackson, Morton. • Feet 3. Grayish clay in thin layers 5 2. Lignite and lignitic clay 6 1. White sand, cross bedded with clay partings 15 In another outcrop southeast of the above mentioned point, there are exposed about 6 feet of grayish sticky clay which has resting upon it an alternating bed of clay and sand with a thickness of 20 feet. At one place in this outcrop a fault having a throw of 4 feet is visible. (See Plate XXXIX, B.) The grayish clay has the following chemical composition: TABLE 96. ANALYSIS OF JACKSON CLAY, MORTON. No. 90 Moisture (H 2 0) 7.35 Volatile matter (C0 2 etc.) 10.12 Silicon dioxide (Si0 2 ) 61.82 Iron oxide (Fe 2 Os) v 2.80 Aluminum oxide (A1 2 Os) 12.28 Calcium oxide (CaO) .82 Magnesium oxide (MgO) .54 Sulphur trioxide (SO 3 ) .04 Total 95.77 RATIONAL ANALYSIS. Clay substance 31.06 Free silica 43.04 Impurities 4.20 Clay No. 90 requires 22 per cent of water for plasticity; has a tensile strength, raw, of 81 pounds per square inch; burned, 131 pounds per square inch ; has a total shrinkage of 10 per cent ; and has an absorption of 11.11 per cent. Mixed with 10 per cent coal it has a total shrinkage of 7 per cent; has a tensile strength, raw, of 100 pounds; and has a tensile strength, burned, of 233 pounds per square inch. When mixed with 10 per cent cinders its total shrinkage is 7 per cent; its tensile strength, raw, is 100 pounds, and burned is 235 pounds per square inch. 232 CLAYS OF MISSISSIPPI. SUNFLOWER COUNTY* GEOLOGY* Sunflower County lies within the Yazoo basin and its entire sur- face formation is alluvium. Sandy loams and stiff black clays form the surface. Underlying the alluvial deposit are the clays, sands and sandstones of the Claiborne and Wilcox. CLAY INDUSTRY. Indianola . — The alluvial clays are being used at Indianola in the manufacture of brick. Two plants are in operation at this point ; both of them use the dry -press process of manufacture. In the pit used by the Indianola Brick a*nd Tile Company the follow- ing strata are exposed: Section of Clay Pit , Indianola. Feet 3. Yellowish loam % 3 2. Dark colored clay (buckshot) 2 1. Yellowish clay 6 A sample of No. 1 was taken for analysis with the following result: TABLE 97* ANALYSIS OF ALLUVIAL CLAY INDIANOLA. No. 54 Moisture (H 2 0) . . . . . 5.00 Volatile matter (C0 2 etc.) 7.57 Silicon dioxide (Si0 2 ) * . . 60.00 Iron oxide (Fe 2 0 3 ) . 4.62 Aluminum oxide (A1 2 0 3 ) 20.00 Calcium oxide (CaO) .80 Magnesium oxide (MgO) .47 Sulphur trioxide (S0 3 ) .85 Total 99.31 RATIONAL ANALYSIS. Clay substance 50.60 Free silica 36.48 Impurities 6.74 Clay No. 54 requires 20 per cent of water to render it plastic. It loses 13 per cent in weight in burning. In the raw state its tensile strength is 262 pounds. The burned brickettes have a strength of CLAYS OF NORTHERN MISSISSIPPI, 233 390 pounds. It bums to a red color but fuses at a moderately low temperature. Great care must be exercised in drying and burning to prevent cracking and swelling. The stratum is not used alone but is mixed with the overlying leaner clay, and more satisfactory results are obtained. The effect of the top clay is to facilitate drying and lessen shrinkage. When burned hard the center of the bricks are steel blue in color. The hard-burned bricks have a water absorption of 9.3 per cent. The Sunflower Brick Manufacturing Company also operates a plant at Indianola. The plant is located on the line of the Southern Railway, west of town. The pit as far as opened at the time of the visit of the writer exhibited the following: Section of Clay Pit , Indianola. Feet 2. Light grayish, loamy clay 3 1. Dark colored clay 6 Samples of clay were taken from both of these layers. The analyses are given below. Analysis No. 52 was made from layer No. 1 and NO. 53 from layer No. 2. TABLE 98. ANALYSES OF BRICK CLAYS, INDIANOLA. No. 52 Moisture (H 2 0) 7.27 Volatile matter (C0 2 etc.) 2.40 Silicon dioxide (Si0 2 ) 71.17 Iron oxide (Fe 2 0 3 ) 6.04 Aluminum oxide (A1 2 0 3 ) 10.06 Calcium oxide (CaO) 1.00 Magnesium oxide (MgO) 1.16 Sulphur trioxide (S0 3 ) .48 No. 53 2.15 4.85 71.67 7.90 8.10 .90 .94 .62 Total 99.58 97.13 RATIONAL ANALYSIS. Clay substance 25.47 Free silica 11.83 Impurities 8.68 20.49 62.15 10.36 Brickettes of clay No. 52 lose 14 per cent in weight in being burned. The clay becomes plastic when mixed with 22 per cent of water. It has a total shrinkage of 10 per cent. The tensile strength of the raw clay is 300 pounds. 234 CLAYS OF MISSISSIPPI. Clay No. 53 is rendered plastic by the addition of 20 per cent of water. The air shrinkage is about 5 per cent. The tensile strength of the raw clay is 100 pounds. The burned brickettes have a strength of 300 pounds per square inch. Moorhead . — A sample of alluvium clay of the plastic “buckshot” type was collected near the plant of the Moorhead Manufacturing Com- pany at Moorhead. The clay is bluish black in color and of very fine grain. The amount of water required to render it plastic is 25.89 per cent. In the raw state the clay has a tensile strength of 142 pounds. When burned hard it has a strength of 840 pounds. The total amount of shrinkage is 15 per cent. The chemical composition is given below: TABLE 99. ANALYSIS OF BUCKSHOT CLAY, MOORHEAD. No. 115 Moisture (H 2 0) 7.20 Volatile matter (C0 2 etc.) 8.00 Silicon dioxide (Si0 2 ) 58.16 Iron oxide (Fe 2 Os) 4.95 Aluminum oxide (A1 2 0 3 ) 17.25 Calcium oxide (CaO) 3.22 Magnesium oxide (MgO) .27 Sulphur trioxide (S0 3 ) .27 Total 99.32 RATIONAL ANALYSIS. Clay substance 43.64 Free silica 31.77 Impurities 8.71 TATE COUNTY. GEOLOGY. The entire subsurface of Tate County is the Wilcox (Lagrange) division of the Tertiary. The mantle-rock formations are the La- fayette, the Loess, the Columbia and the Yazoo alluvium. The last two are the sources of the brick material. CLAY INDUSTRY. Senatobia . — The brown loam clay is used at Senatobia in the man- ufacture of brick. T. B. Montgomery and Son operate a plant at this point. The plant was established in 1900. The clay is tern- CLAYS OF NORTHERN MISSISSIPPI. 235 pered in soak pits and molded in a soft-mud machine operated by horse power. The brick are placed upon pallets and racked in cov- ered racks for drying. They are burned in up-draft kilns of the rec- tangular form. The local stratigraphy is disclosed by the well record at the plant: Record of Montgomery Well. Thickness Depth Feet Feet 4. Brown loam (Columbia) 12 12 3. Gravel (brown and white chert, Lafayette) 3 15 2. Red sandy clay 8 23 ' 1. White sand, water-bearing 17 40 The brown loam and the underlying clay of the Columbia are well developed in Tate County. With the proper selection and mixing of the loam and clay a good quality of brick may be obtained. TIPPAH COUNTY* GEOLOGY. The Ripley formation comprises the bed-rock of the eastern part of Tippah County, while the western part is underlain by the basal division of the Eocene. The mantle rock formations are the Lafay- ette sands and clays and the brown loam of the Columbia. The latter forms the chief source of brick clay under the present development. CLAY INDUSTRY. Ripley . — At Ripley the Ripley Brick Manufacturing Company uses a surface clay from the Columbia in the manufacture of brick. The stiff -mud, end-cut machine of the auger type is used. The brick are burned in rectangular up-draft kilns. From the clay pit and the well at the brick yard the following local stratigraphic conditions were determined:. Section of Clay Pit , Ripley. Feet 5. Soil 1 4. Loam 2 3. Brownish clay with buckshot at bottom 10 2. Sand (water-bearing) 1 1. Limestone with shells 2 All of the layers above No. 1 belong to the mantle rock, belongs to the bed rock. No. 1 236 CLAYS OF MISSISSIPPI. A sample of clay from No. 3 has the following chemical properties TABLE 100. ANALYSIS OF BRICK CLAY, RIPLEY. No. 110 Moisture (H 2 0; 2.85 Volatile matter (C0 2 etc.) 2.80 Silicon dioxide (Si0 2 ) 82.20 Iron oxide (Fe 2 Os) 4.62 Aluminum oxide (Al 2 03 ) 6.24 Calcium oxide (CaO) . 1.05 Magnesium oxide (MgO) .90 Sulphur trioxide (SO 3 ) .04 Total 100.20 RATIONAL ANALYSIS. Clay substance 15.78 Free silica 74.87 Impurities 6.61 The above mentioned clay requires 17 per cent of water to render it plastic. Its total shrinkage is 6 per cent. The tensile strength of the raw brickettes is 168 pounds per square inch. When soft burned the strength is 135 pounds per square inch. Air dried brick lose 2 per cent in weight in being' dried at 10U° F. and 5 per cent more in burning. TUNICA COUNTY. GEOLOGY. Tunica County lies wholly within the Yazoo basin. Its surficial formation is the Post-Pleistocene alluvium. The bed rock formation probably belongs wholly to the Wilcox. CLAY INDUSTRY. Robins onville . — The clays of the alluvial deposit are used at Rob- insonville in the manufacture of brick and drain tile. The brick are molded in a machine of the stiff -mud type, and burned in a beehive kiln. There are two principal types of the Yazoo alluvium in Tunica County. The sandy type, which is found near the streams, and the clayey interstream-area type. Because of the shifting of the streams or of temporary currents across the Yazoo basin during the building of the flood plain, both of these types may be found at the same place succeeding each other every few feet in a vertical section. These two types arejmixed in the manufacture of brick and drain tile. CLAYS OF NORTHERN MISSISSIPPI. 237 UNION COUNTY. GEOLOGY. The bed-rock formations of Union County are the Selma chalk and the Ripley in the eastern part, and the Wilcox in the western part. The mantle rock formations are the Lafayette and the Colum- bia. Pontotoc Ridge, which crosses the county from north to south about the central portion, exhibits the best development of the Lafayette. Clays from both the surficial formations are used in the manufacture of brick in this county. CLAY INDUSTRY. New Albany . — Two brick manufacturing plants are located at New Albany. The Butler Brick Manufacturing Company has a. clay pit on the west side of a small ridge extending south of New Albany. The clay on the ridge is probably Lafayette, though the lower portion may be residual Ripley. The brick yard well pierced about 20 feet of this clay. The slopes of the Lafayette are covered with a mantle of brown loam, which increases in thickness toward the valley. The red-colored Lafayette clay is too sticky to be used in the soft-mud process of brick making. A sample of the Lafayette clay has the following chemical properties: TABLE 101. ANALYSIS OF LAFAYETTE CLAY, NEW ALBANY. No. 109 Moisture (H 2 0) . 2.27 Volatile matter (C0 2 etc.) 2.77 Silicon dioxide (Si0 2 ) 80.13 Iron oxide (Fe 2 0 2 ) 4.62 Aluminum oxide (Al 2 Os) 9.00 Calcium oxide (CaO) .25 Magnesium oxide (MgO) .14 Sulphur trioxide (S0 3 ) .09 Total 99.27 RATIONAL ANALYSIS. Clay substance 22.77 Free silica 69.55 Impurities 5.10 The physical properties of clay No. 109 are as follows: It requires 17 per cent of water for plasticity. It has a total shrinkage of 5 per cent. Its tensile strength, raw, is 50 pounds per square inch. 238 CLAYS OF MISSISSIPPI. The brown clay of the slope has been used by the above mentioned company in the manufacture of brick. The composition of this clay is given below: TABLE 102. ANALYSIS OF BRICK CLAY, NEW ALBANY. Moisture (H 2 0) Volatile matter (C0 2 etc.) Silicon dioxide (Si0 2 )' Iron oxide (Fe 2 Os) Aluminum oxide (Al 2 Os) . Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SO 3 ) No. 108 1.05 2.85 85.24 3.50 .71 3.69 2.00 .86 Total 99.90 RATIONAL ANALYSIS. Clay substance Free silica Impurities 1.79 84.41 10.05 Clay No. 108 requires 16 per cent of water for plasticity; has a shrinkage of 2 per cent, and has a tensile strength, raw, of 50 pounds. A clay from a small valley is now being used at the Butler Brick Plant. The clay is prepared by the use of a disintegrator and granu- lator. It is tempered in a pug mill and molded in a soft-mud machine operated by steam power. The brick are burned in rectangular up- draft kilns of the clamp type. A sample of clay from the valley has the composition given below: TABLE 103. ANALYSIS OF BRICK CLAY, NEW ALBANY. No. 106 Moisture (H 2 0) 1.10 Volatile matter (C0 2 etc.) 2.67 Silicon dioxide (Si0 2 ) 85.29 Iron oxide (Fe 2 03 ) 3.44 Aluminum oxide (Al 2 Os) 4.44 Calcium oxide (CaO) .44 Magnesium oxide (MgO) .09 Sulphur trioxide (SO3) .17 Total 97.64 RATIONAL ANALYSIS. Clay substance 11.23 Free silica 80.07 Impurities 4.14 Plate XL, A. VICKSBURG LIMESTONE, VICKSBURG, DISTANT VIEW. B. VICKSBURG LIMESTONE, VICKSBURG, NEAR VIEW. CLAYS OP NORTHERN MISSISSIPPI. 239 The physical properties of clay No. 106 are: Water required for plasticity, 16 per cent; air shrinkage, 1 per cent; fire shrinkage, 1 per cent or less; tensile strength, raw, 65 pounds per square inch. The Union County Brick and Tile Company has a plant a short distance south of the Butler yard. The clay in its pit has a thickness of 10 feet. The upper part is a brown loam clay, and the lower portion is red Lafayette. The top clay cannot be used alone in the manu- facture of dry -pressed brick. The best results are obtained by using the bottom clay. A sample of the red clay has the composition given below : TABLE! 1 04. ANALYSIS OF LAFAYETTE CLAY. NEW ALBANY. No. 107 Moisture (H 2 0) 2.55 Volatile matter (C0 2 etc.) 4.05 Silicon dioxide (Si0 2 ) 77.99 Iron oxide (Fe 2 Os) 6.25 Aluminum oxide (Al 2 03 ) 8.37 Calcium oxide (CaO) .06 Magnesium oxide (MgO) .27 Sulphur trioxide (SO 3 ) .51 Total 100.05 RATIONAL ANALYSIS. . Clay substance 21.17 Free silica 68.15 Impurities 7.09 Clay No. 107 has an absorption of 13.79 per cent; requires 18 per cent of water for plasticity; has a total shrinkage of 3J per cent; has a tensile strength, raw, of 60 pounds per square inch, and burned of 50 pounds. WARREN COUNTY. GEOLOGY. The bed rock formations of Warren County belong to the Vicks- burg, Jackson and Grand Gulf stages of the Tertiary period. In the bluffs near the Mississippi and Yazoo Rivers in this county there are numerous exposures of Vicksburg limestone. Such outcrops are found both north and south of the city of Vicksburg. The road leading north from Vicksburg to the National Military Cemetery passes along the foot of the bluff, the lower portion of which is formed by an 240 CLAYS OF MISSISSIPPI. almost unbroken wall of Vicksburg limestone. (See Plate XL VI I.) The limestone consists of 5 to 6 layers, which are interbedded with marl. The limestone beds vary in thickness from 1 to 6 feet. A dark laminated clay or marl is exposed in a creek bed about 20 feet below these limestones. At a point where the cemetery road ap- proaches the nearest point to Finnie Lake, the outcrop of limestone is capped with 30 feet or more of shell marl. The shells are very abundant. The upper portion of the marl contains lens-like clay stones which are brown on weathered surfaces and purple on fresh fractures. The surfaces of these stones are generally channelled and irregular. The marl contains some ironstone concretions of irregular shape. The freshly exposed marl is bluish gray in color. Under the action of the weathering agents it changes first to dark red or purple and finally to yellow. The upper part of the bluff is capped by 20 feet or more of Loess. In other places it is thicker. Resting upon the Loess at Vicksburg there is a brownish colored clay which is used in the manufacture of brick. This clay is probably a residual product resulting from the decomposition of the Loess. CLAY INDUSTRY. Vicksburg . — The J. D. Tanner Brick Manufacturing plant was established about 1880. The brick are manufactured by the soft- mud process, being molded by hand. The clay is tempered in a ring pit. The brick are burned in rectangular up-draft kilns. The clay pit, which is located on a hill, has the following strati- graphy, the divisions not being very clearly defined: Section at Tanner Brick Plant , Vicksburg. Feet 4. Soil 1 3. Loamy clay, grading into 2 2 2. More plastic clay 4 1 . Loess 2 + No. 1 has a thickness of 50 feet or more in some places. It lacks plasticity and is not used by itself in the manufacture of brick. The remainder of the section seems to be the residual product, resulting from the weathering of the Loess. While retaining some of its physical characters, it has lost much of its soluble matter. Especially has the amount of calcareous matter been greatly reduced. The lime con- Plate XLI. EROSION IN BROWN LOAM AND LOESS, NATIONAL PARK, VICKSBURG CLAYS OP NORTHERN MISSISSIPPI. 241 cretions and the gastropod shells, so characteristic of the Loess, have disappeared. There is a decided gain in clay substances, conse- quently a gain in plasticity. The joint structure has been developed. In the manufacture of soft-mud brick at the Tanner plant it is not possible to use the more plastic clay alone, so it is mixed with the Loess in the proportion of 1 foot of the latter to 5 feet of the former. Some of the physical properties of the clay are as follows: Its total shrinkage is only 3 per cent, practically all of which is air shrinkage. The raw clay has a tensile strength of 66 pounds per square inch. The burned brickettes have a tensile strength of 144 pounds per square inch. The addition of 23 per cent of water is necessary for plasticity. The loss of weight in passing from an air dried to a burned condition is 4 per cent. The burned brickettes absorb 12 per cent of water. The Gregory Brick Manufacturing plant, established in 1906, is located in the southern part of Vicksburg. The clay used is taken from a pit on the side of a small depression near the plant. The clay changes from the surface downward from a sandy loam to a plastic joint clay. The Loess lies below the clay. It contains white lime concretions of irregular shapes, somewhat resembling potatoes with their protuberances. White gastropod shells are also abundant in the Loess. The clay is tempered in a ring pit and molded by hand. The brick are burned in rectangular up-draft kilns. The Beck Brick Manufacturing plant is located on one of the Loess ridges in the southeastern part of Vicksburg. The plant was established in 1889. They use clay and loess in the proportion of 1 part of loess to 5 parts of clay. The treatment of the clay is similar to that of the other plants. It is tempered in the ring pit and molded by hand. After being dried in the open yard, the brick are burned in rectangular up-draft kilns. The Garbish Brick Manufacturing Company operates a plant in the northern part of Vicksburg. The residual Loess clay is carted from the hill which rises above the low ground next to the river. The clay is mixed with the Loess in the proportion of 12 loads of clay to 3 loads of Loess. The Thornton Press Brick Company operated a plant at Vicks- burg until 1905, when the plant was burned. The residual Loess clay was used in the manufacture of dry-pressed brick. 242 CLAYS OF MISSISSIPPI. WASHINGTON COUNTY, GEOLOGY, Washington County lies wholly within the Mississippi flood plain in the Yazoo delta. Its surface is occupied by the alluvium deposited during overflows from the river. The surficial material is of two types, viz., the sandy loams, so well represented on the borders of Deer Creek, and the dark “buckshot” clays, well developed in the Black Bayou region. CLAY INDUSTRY, Elizabeth . — A sample of clay collected from near the station at Elizabeth in Washington County has the following chemical com- position : TABLE 105. ANALYSIS OF CLAY. ELIZABETH. No. 58 Moisture (H 2 0) ^ 3.06 Volatile matter (C0 2 etc.) 3.94 Silicon dioxide (Si0 2 ) 69.22 Iron oxide (Fe 2 03 ) 5.90 Aluminum oxide (Al 2 03 ) 13.35 Calcium oxide (CaO) 2.75 Magnesium oxide (MgO) 1.15 Sulphur trioxide (SO 3 ) .48 Total 99.85 RATIONAL ANALYSIS. Clay substance 33.77 Free silica 53.53 Impurities 10.28 The physical properties of the clay, so far as determined, are as follows: It has a total shrinkage of 5 per cent when burned to a hard state. It requires 19 per cent of water to render it plastic. The brickettes lose 10 per cent in weight in burning. They bum to a cherry red and are without cracks or checks. The tensile strength of the raw clay is 200 pounds per square inch. The burned brickettes have an absorption of 14 per cent. The clay is of fine grain and does not contain any gravel or large particles. A sandy type and -a fat type are found within a short distance of each other, and are thus accessible for mixing. The railroad facilities at Elizabeth are excel- lent. This point is worthy of the investigation of those desiring to engage in the manufacture of brick and drain tile. Greenville . — At Greenville the alluvial clay has been used in the manufacture of brick by the Greenville Dry Press Brick Company. Plate XLII. TYPICAL LOESS TOPOGRAPHY, VICKSBURG. CLAYS OF NORTHERN MISSISSIPPI. 243 The clay is of a dark color and belongs to the “buckshot” type. The brick are molded in a dry-press machine and burned in up-draft clamp kilns. A sample of clay from this pit has the following chem- ical composition : TABLE 106, ANALYSIS OF ALLUVIAL CLAY, GREENVILLE. No. 49 Moisture (H 2 0) 4.21 Volatile matter (C0 2 etc.) 11.78 Silicon dioxide 58.82 Iron oxide (Fe 2 0 3 ) 11.30 Aluminum oxide (A1 2 0 3 ) 9.70 Calcium oxide 1.40 Magnesium oxide (MgO) 2.01 Sulphur trioxide (S0 3 ) > .50 Total 98.72 RATIONAL ANALYSIS. Clay substance 24.54 Free silica 47.42 Impurities 15.21 The burned brickettes have an absorption of 11.11 per cent. The clay slacks slowly. When stirred wet it forms hard clods. The clay requires 19 per cent of water to render it plastic. It has a total shrinkage of 10 per cent. In the raw state its brickettes have a ten- sile strength of 190 pounds per square inch When burned hard they are red in color and have a tensile strength of 632 pounds. In the process of granulation the clay may be reduced to spherical grains, which in the molding process are not entirely obliterated. Under such conditions the soft -burned brick may crumble. When the brick are hard-burned the grains are destroyed. Great care must be exer- cised in burning the clay at high temperature to avoid swelling and cracking. Hampton . — A sample of alluvial clay collected from near the station at Hampton belongs to the sandy loam type and has the fol- lowing physical properties: The total shrinkage is about 3 per cent. Its tensile strength, raw, is 53 pounds, and when burned it has a strength of 116 pounds. It requires 19.1 per cent of water to render it plastic. The clay loses 26 per cent of its weight in drying and burning, 7 per cent being lost between the air-dried and the burnt states. This sample was taken about 1 foot below the surface. Another sample taken from a lower level has a total shrinkage of 4 244 CLAYS OF MISSISSIPPI. per cent. Its loss of weight in drying and burning is 24 per cent. Its absorption is 14.81 per cent. In the raw state it has a tensile strength of 180 pounds per square inch, and when soft-burned its strength is only 110 pounds. In grain it is coarse, but does not con- tain any loose particles. WEBSTER COUNTY. GEOLOGY. Webster County lies wholly within the borders of the Wilcox (Lagrange) division of the Tertiary. The formation consists of clays and unconsolidated sands with intercalated beds of lignite. Many good pottery clays occur in the formation. A small hand pottery at Cumberland manufactures a general line of stoneware. One of the clays from this formation is used at Maben in the manufacture of white brick. The surface formations of the county consist of the sands and clays of the Lafayette and the loams of the Columbia. The analysis of the white clay used at Maben in the manufacture of white brick may be seen on page 212. WINSTON COUNTY. GEOLOGY. Winston County lies mainly within the Wilcox-Eocene, though there is a small area of Tallahatta buhrstone in the southwestern comer. The surficial deposits are of Lafayette and Columbia age. The Wilcox (Lagrange) contains some good beds of white pottery clays. It also contains beds of lignite. The chemical composition of one of the white pottery clays from the J. A. M. Loyd pottery pit near Webster is given below: TABLE 107. ANALYSIS OF POTTERY CLAY NEAR WEBSTER. No. 68a Moisture (H 2 0) Volatile matter (C0 2 etc.) Silicon dioxide (Si0 2 ) Aluminum oxide (Al 2 Os). Iron oxide (Fe 2 Oa) Calcium oxide (CaO) Magnesium oxide (MgO) . . Sulphur trioxide (SO 3 ) .47 9.24 59.82 27.19 1.26 .49 .37 .31 Total 99.15 CLAYS OF NORTHERN MISSISSIPPI. 245 RATIONAL ANALYSIS. Clay base 68.90 Free silica 18.11 Fluxing impurities 2.12 CLAY INDUSTRY* Louisville . — The surface clays are used at Louisville in the manu- facture of brick by two companies. The Storer and Miller Company have a yard located north of town on the line of the Mobile, Jackson and Kansas City Railroad. The clay used is a red clay, probably of Lafayette age. The upper portion is sandy. There seems to be about 6 feet of residual clay with a red and white clay below. The clay at this point is prepared in a disintegrator and granulator, and tempered in a pug mill. It is molded in an end-cut stiff -mud machine. The brick are dried in covered racks and burned in up-draft kilns. Langley Brothers operate a brick plant south of Louisville. The clay used is a surface loam which is mixed with a white plastic clay underlying the loam. The general stratigraphy of the locality is revealed in a well near the pit. Section of Well at Langley Brothers Brick Plant , Louisville. Feet 3. Surface loam (yellow) 6 2. Red and white clay and sand 15 1. Blue sandy clay with lignite 4 YALOBUSHA COUNTY* GEOLOGY* The Wilcox (Lagrange) formation forms the subsurface of Yalo- busha County. The surficial deposits are Lafayette and Columbia. The brown loam of the latter is the principal clay used in the manu- facture of brick in this county. CLAY INDUSTRY. Water Valley . — At Water Valley the clay of the surface formations is used in the manufacture of brick by the Norris Brick Manufacturing Company. The plant was established in 1904. The brick are molded in a stiff-mud machine of the plunger type. They are dried in open air sheds and burned in rectangular up-draft kilns. The brick 246 CLAYS OF MISSISSIPPI. are sometimes dried in the sun without checking. The clay in the pit is of two kinds, a red clay at the bottom of the pit, probably La- fayette, and a brown clay overlying the red. The red clay cannot be used alone as it is too plastic. It may be used when mixed with the more non-plastic brown loam lying above. YAZOO COUNTY. GEOLOGY. The chief bed rock formation of Yazoo County belongs to the Jackson division of the Eocene. It consists of clays, marls, sands and impure limestones, usually very fossiliferous. The bed rock is largely concealed by mantle rock belonging to the Pliocene, Pleistocene and Post-Pleistocene epochs. To the Pliocene may be assigned a series of cross-bedded sands, gravels and clays constituting the Lafayette formation. Both laterally and vertically the constituent materials of the formation vary greatly and pure beds of sand may be succeeded by pure beds of gravel and clay or by mixtures of the three. The colors are predominantly red, orange and yellow. The thickness of the formation rarely exceeds 50 feet. The Pleistocene is represented by the Loess and possibly by the Natchez formation, though the latter has not been definitely differentiated from the Lafayette in Yazoo County. The Loess is a very fine silt which in the process of weather- ing produces a surface loam with a clay substratum. The Columbia loam rests upon the Loess and, wherever the true Loess is absent, upon older formations. The flood plain of the Mississippi and the Yazoo Rivers in this county, called the Yazoo delta, is covered with alluvial material of Post-Pleistocene age. There are two types of the alluvial material, a sandy loam and a plastic clay. The loam is generally light in color and of greater weight and is found near the streams. The clay is dark, light in weight and of finer grain and found in the interstream areas. Topographically Yazoo County may be divided into the plain portion, that part included in the Yazoo Delta, and the hill portion, that section of the county lying east of the Yazoo River. The surface of the county rises by means of an abrupt escarpment from the flood plain to the hill country. The flood plain area forms an exceeding level plain which lies about 100 feet above sea level. CLAYS OF NORTHERN MISSISSIPPI. 247 The escarpment rises to a height of 250 to 300 feet above this plain. The surface descends from the escarpment toward the valley of Black River. The river front of the escarpment presents a crenulated margin produced by small streams which have cut V-shaped valleys in its front. The position of the larger streams is marked by valleys with small flood plains which merge into the larger plain. The principal brick materials of the county are found in the residual clay of the Loess, and the clays of the delta, which may also be used for road ballast. Doubtless there are also deposits of the Lafayette and some residual clays of the Jackson which could be used in the manufacture of brick. CLAY INDUSTRY. Yazoo City . — A residual clay overlying the Loess at Yazoo City is used by the Montgomery Land Company in the manufacture of dry-pressed brick. The Loess assists in forming the bluffs along the border of the flood plain east of Yazoo City. These bluffs are mantled by residual clay, which is thin on the crest of the hills and becomes thicker in the depressions. On the steeper slopes it rarely ever reaches a thickness of 3 feet. In the depressions, however, a thick- ness of 8 feet is not uncommon. The clay substance usually increases toward the bottom of the pit. The Loess beneath is noticeably non- plastic as compared with the clay. The Jackson strata are revealed in outcrops near the base of the hills. The weathered surfaces o£ the exposures exhibit a gray joint -like clay containing shells. The clay is very plastic and seems to be free from sand. The Lafayette gravels rest upon the Jackson marls. The Lafayette covers the Jackson to the depth of 10 to 40 feet. The chemical composition of the surface brick clay is given in the analysis below: TABLE 108. ANALYSIS OF SURFACE BRICK CLAY, YAZOO CITY. No. 60 Moisture (H 2 O) 2.37 Volatile matter (CO 2 etc.) 4.37 Silicon dioxide (Si 02 ) 72.65 Iron oxide (Fe 20 j) 5.81 Aluminum oxide (AI 2 O 3 ) 11.25 Calcium oxide (CaO) 1.12 Magnesium oxide (MgO) 1.62 Sulphur trioxide (SO 3 ) .30’ Total 99.49 248 CLAYS OF MISSISSIPPI. RATIONAL ANALYSIS. Clay substance 28.46 Free silica 59.42 Impurities 8.85 The above mentioned clay has a tensile strength of 85 pounds per square inch in the raw state, and 175 pounds per square inch in the soft-burned condition. Its total shrinkage is 4 per cent of which 3 per cent is air shrinkage. It requires 18 per cent of water to render it plastic. The soft-burned brickettes absorb 15.25 per cent of water. TABLE 109. Name of Firm 1 . 2 . 3. 4. 5. 6 . 7. 8 . 9. 10 . 11 . 12 . 13. 14. 15. 16. 17. 18. 19. 20 . 21 . 22 . 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. Clermont Brick Jesty Brick SSISSIPPI CLAY WORKERS. Town County Product .Pontotoc . .Greenwood . . .Leflore “ .Baldwyn “ .Bay St. Louis. . . “ .Vicksburg . . .Warren “ .Grenada . . .Grenada . . . . “ .Meridian . . . Lauderdale . . . “ .Booneville . . .Prentiss . . . . Brick and tile . Crenshaw Brick . Brookhaven “ . Hattiesburg . . . Perry. “ .New Albany “ .Jackson “ . Sardis . . .Panola “ . Amory . Grenada “ . Gulfport “ . Centerville “ .Charleston “ . Clarksdale . . . . Brick and tile . Biloxi . Macon . Columbus . .Lowndes “ .Natchez . . Adams “ . Corinth “ .Minter City . Edwards . Holly Springs . . . . . . Marshall . “ . Rienzi “ . Femwood “ . Vicksburg “ . Lumberton . . Lamar “ . Greenville . “ . Vicksburg . .Warren . Holcomb “ .Newton “ . Okolona . “ . Hazlehurst . . Copiah . Starkville “ . Biloxi . . y *• . Indianola “ .Winona . . Montgomery . . “ CLAYS OF MISSISSIPPI 249 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66 . 67. 68 . 69. 70. 71. 72. 73. 74. 75. 76. 77. 77a 78. 79. 80. 81. 82. 83. 84. 85. 86 . 87. 88 . 89 90. 91. 92. 93. 94. 95. 96. 97. 98. TABLE 109 — Continued. DIRECTORY OF MISSISSIPPI CLAY WORKERS— Continued. Name of Firm Landon Brick' & Tile Co Langley Brick Co Laurel Brick & Tile Co Leakesville Brick Co Love Wagon Co Lowery & Berry Brick Co Maben Brick Co Magnolia Brick Co Montgomery Brick Co Montgomery Land Co Mt. Olive Brick Co Natchez Brick Co Nettleton Manufacturing Co ... . New Houlka Brick Co Norris Brick Manufacturing Co. Ocean Springs Brick Co Oxford Brick & Tile Co Pope Brick Manufacturing Co . . Quitman Brick Co Rheinhart Brick & Tile Co Ripley Brick Manufacturing Co . Riverside Brick Co Robinsonville Brick & Tile Co. . Saltillo Brick Manufacturing Co Smith Brick Co Storer & Miller Brick Co Storer & Miller Brick Co Success Brick & Tile Co Summit Brick Co Sunflower Brick Co. Tanner Brick Co Taylor & Thomas Brick Co Tayior Brick Co Thrasher Brick Co Thornton Brick Co Tubbs Brick Co Union County Brick & Tile Co. . Utica Brick Manufacturing Co . . Vaiden Brick & Tile Co Valley Brick & Tile Co. Vardaman Brick Co Verona Brick & Tile Co Weems Brick Co Welch-Trotter Brick Co West Point Brick Co White & May Brick Co Woodville Brick Co Cumberland Pottery Holly Springs Stoneware Co ... . Allison Pottery Co Davidson Pottery Kennedy Pottery % Stewart Pottery Loyd Pottery Lockhart Pottery Co Moorhead Manufacturing Co ... . Summerford Pottery T own County Product .Landon Harrison “ . Louisville W inston “ .Laurel Jones “ . Leakesville Greene “ . Durant Holmes “ .Blue Mountain Tippah “ . Maben Oktibbeha “ .Magnolia Pike “ . Senatobia Tate “ .Yazoo Yazoo “ .Mt. Olive Covington “ . N atchez Adams “ .Nettleton Lee “ .New Houlka Chickasaw “ .Water V alley Y alobusha “ .Ocean Springs Jackson “ . Oxford Lafayette “ . Houston Chickasaw “ . Quitman Clarke “ . Clarksdale Coahoma Brick and tile . Ripley Tippah Brick . Hattiesburg Perry “ .Robinsonville Tunica Brick and tile . Saltillo Lee Brick . Canton Madison “ . Kosciusko Attala “ . Louisville Winston “ . Greenwood Leflore “ .Summit Pike “ . Indianola Sunflower “ . Vicksburg W arren “ . Crystal Springs Copiah “ . J ackson H inds ‘ . Thrasher Prenti ss “ . V icksburg W arren “ . Amory Monroe “ .New Albany Union “ .Utica Hinds “ .Vaiden Carroll “ .Lake View DeSoto “ . V ardaman Calhoun “ .Verona Lee “ .Sun Scott “ .West Point Clay “ .West Point Clay “ . McComb City Pike “ .Woodville Wilkinson “ . Cumberland Webster Stoneware . Holly Springs Marshall " .Holly Springs Marshall “ .Miston Itawamba “ . M iston Itawamba “ . Perkinsville Winston “ Webster r. . . .Winston “ Lockhart Lauderdale “ Moorhead Sunflower Drain tile Miston Itawamba Stoneware ACKNOWLEDGMENTS, The writer of this report desires to express his very great obliga- tions to the men engaged in the manufacture of clay wares in Missis- sippi for the generous and cordial way in which they have responded to requests for information necessary to the completion of this report. The chemical work included in this report was done under the direction of Dr. W. F. Hand, State Chemist, and to him and his corps of assistants all credit is due. A few chemical analyses derived from other sources are credited at their proper places. The writer is indebted to Dr. Calvin S. Brown for some reports of brick plants and for the samples of lignites mentioned in the mono- graph. Also to A. F. Crider, Director of the Survey, for reports of brick plants, for reading the manuscript and for other courtesies extended. . In the preparation of the report the writer is under special obli- gations to the following reports and works on ceramics: Treatise on Ceramic Arts, Bourry, 1901. Clays of Alabama, Bui. 6, Ala. Geol. Sur., 1900, Smith and Reis. Clays of Iowa, la. Geol. Sur., Vol. XIV, 1904, Beyer and Williams Clays of Missouri, Mo. Geol. Sur. XI, 1896, Wheeler. Clays of New Jersey, N. J. Geol. Sur. VI, Kummel, Reis and Knapp. Economic Geology of the United States, Reis, 1905. Clays of Georgia, Ga. Geol. Sur., Ladd, 1898. Clays of Pennsylvania, Hopkins, 1897. Geology of Clays, Rolfe, in Brick, Nov., 1906. Earth History, Chamberlin and Salisbury (Geology). Efflorescence of Brick, Am. Cer. Soc., Vol. VIII, Jones. Also other papers printed in Brick and Clay Worker. INDEX, A. Page. Aberdeen. _ 211 Absorption 134 tests 135 Ackerman 182 Acknowledgments 250 Adulterant clay 40 Adobe clay 1 33 • Agricultural College 220 Air shrinkage 62 Alabama coals 126 Alcorn County 169 geology of 169 clay industry. __ 170 Alkalies 49 Allison Stoneware Co 208 Alumina 47 Amory •_ 212 Analyses of clays. -44, 156, 157, 159, 160, 161, 163, 165, 170, 174, 175, 177, 178, 179, 182, 184, 185, 487, 188, 190, 191, 192, 196, 198, 199, 200, 201, 204, 205, 207, 208, 209, 210, 212, 215, 216, 217, 218, 219, 220, 222, 224, 225, 228, 229, 230, 231, 232, 233, 234, 236, 237, 238, 239, 242, 243, 244. 247. ultimate 46 mechanical 75 of tripoli 154 of limestone 154, 155, 158, 163, 171, 175, 180, 181, 220 , 222 . of shale 155 of sandstones. __ 159 of claystones. 164 Anthracite 126 Attala County 172 geology of 172 clay industry .172-173 Artificial dryers 118 Auger brick machine 102 B. Ball mills 92 Ballast clay 140 Page. Banks cited 133 Barnett clay 163 Batesville 224 Basalt 28 Beehive kilns 122 Beyer cited. 76, 94, 112 Bledsoe Brick Co. 189 Beck Brick Co 241 Bluff formation... 167 Bonding power 77 Booneville — 226 Brick Co 226 Bowlders 25 Brandon... 1 227 Breccia. _ 27 Brick, properties of. 133-151 absorption. 134 clay 39 cracked 144 crushing strength 134 defects of color. 145 defects of form. 143 defects of structure 148 early history of 13 effloresence in 146 granulations in 150 impact strength of 136 kiln, white in 146 laminations in 150 light color in 145 in construction work 141 size of 138 swollen 143 tensile strength... 137 tests of 133 transverse strength 137 varieties in a kiln 141 wall, white in 147 warped. _ 144 weight of. _ . . 138 machines. . 97-108 Beehive kilns 122 Beyer cited.- 76, 94, 112 C. Calcite 56 Calcium oxide 48 252 iNbfex. Page. Page. Calorific value of coals 123- 129 clay — continued. value of lignites __ 130 shrinkage of __ 61 Camp Brick Co 212 structure of.. 61 Canton 206 specific gravity. 65 Carl Brick Co __ 189 taste 67 Cement clay 40 tensile strength .. 77-80 Cenozoic era 160 transported 35 Chalk 27 uses _ 39-40 Chemical components of clay_ 43 Clay County. 175 elements of clay_--_ 43 geology of _ 175 properties of clay 43 clay industry 175 China clay 40 Coahoma County 183 Chickasaw County _ 180 clay industry 183 geology of 180 geology . ... 183 clay industry. 180 Coal _ 125 Choctaw County 182 classes of 124 geology of _ _ 182 Alabama _ 129 Claiborne stage _ 161- 162 anthracite ... ^ 126 Clamp kilns 121 bituminous. _ __ 126 Clarke, F. W., cited _ 29 calorific value 126 Clarksdale 183 College Hill.. 198 Classification of clay 36 .-39 Color of clays 65 of rocks 27 -28 Columbia formation 167-168 Clay, bonding power of _ 77 Composition of seger cones.. __ 72-73 Carroll County. 173 of the lithosphere. 29 chemical components of. 43 of fuel gases _ 132 chemical elements of 43 Conglomerate 25 chemical properties of 43 -59 Continuous kilns 122 classification of _ 36 Coquina 27 Beyer and Williams 38 Corinth 170 Ladd’s 38 Cretaceous period _ 155 Reis’ _ 37 Crushers. 89 Wheeler’s 36 .-37 Crushing machines _ 93 fusibility. __ _ 70 Cypress pond... 155 color. 65 E. definition. _ 24 Eastport _ 154 dilution of... __ 63 Elizabeth _ 242 feel 67 Eocene formation _ 160 hardness 66 Eutaw formation. occurrence of... 41 F. . odor... _ 67 Feel of clay.. _. _ 67 origin 32 Feldspar. _ _ ... 57 physical properties 61 -81 composition of 57 plasticity 68 Forest. __ . 230 factors of.. 69 1 — 70 Fuel 123 • porosity. 81 calorific value of__ 123 processes of manufacture 83- 123 classes of. _ _ _ _ . 124 residual _ _ _ _ 33 value of gases. _ . .. 132 slaking. _ 67 Fusibility of clay. 70 G. Gas as fuel___ Garbish Brick Co_. Granite Grand Gulf — Granulator. __ Gravel Greenville Greenwood. __ Gregory Brick Co._ Grenada County geology of clay industry. _ Grinding clay . Gypsum H. Hampton. . Hancock Brick Co — Hand moulding Hawkins and Hodges. Haulage - Hematite Hernando...... Hilgard cited. Hinds County Holcomb Holmes County. Holly Springs Hopkins cited. _ Hornblende. Houston Ilmentite. _ - Indianola..- Iron in clay. Iron oxide. - Iuka J- Jackson stage K.' Kaolin Kaolinite. _ _ Kemper County Kilns Kosciusko INDEX. 253 Page. 131 241 26 164 89 25 242 203 24 188 188 189 89 55 243 214 99 180 83-86 53 188 75, 186 191 191 193 208 75 58 181 54 232 52-55 48, 52 156 191 162 . 44-51 50 197 120-122 172 L. Page. Lafayette County. . 197 formation _ 165 Lakeview. 186 Lapilli 28 Lauderdale. _ 199 Lava.. 28 Lee County 200 Leflore County 203 Lexington 193 Loess -.24, 27, 33, 167 Lime group. 27 Limonite 52 Limestone 26, 27, 34 Lithosphere _ 23-29 Loam : 27 Lockhart * 199 Lowndes County _ 205 Loyd pottery 244 M. Maben.... ... . 222 Macon 215 Madison County 206 Magnesia 49 Marble 26,28 Marcasite 54 Marl 24 Marshall County 207 Mechanical analysis. 75 Meridian 200 Mesozoic era 155-159 Metamorphic rock 28 Mica. _ 57 Midway stage 160 Minerals in clay 50-59 Miocene epoch — 164 Mississippi lignites __ 129 Miscellaneous clays 40 Molding .. 97, 102 methods . . 108 Monroe County 211 Montgomery County 210 Moorhead 234 Morton 231 N. Natchez. 167 New Albany 237 254 INDEX. Page. NewHoulka--_ 181 Newton County 214 Nettleton 203 Norris Brick Co 245 Noxubee County 215 O. Odor of clay 67 Oil___ 130 Okolona 180 Oktibbeha County. _ 218 Oligiocene. 163-164 Origin of clay ... 32 Osborne cited 75 P. Paleozoic era _ 153-155 Panola County.. _ 223 Paper clay. _ _ 40 Peaf- 25, 125 Physical properties of clay 61-82 Pick and shovel mining 83 Plasticity. _ 68 Plow and scraper mining 84 Plunger machine 102 Pontotoc 225 Pope Brick Co 181 Porosity 81 Prentiss County 226 Puckett and Lindamood Brick Co_-_ 265 Pug mill 96 Pyrite__ _ 53 Q. Quartzite. 28 Quaternary 165 R. Rankin County 227 State farm 229 Recent deposits 168 Regolith 23,24 Reis, H., cited 44, 45 Repressing 105 Residual clay 33 Rheinhart Brick Co 185 Rienzi___ 171 Ring pit 95 Ripley 235 formation 159 Robinsonville. Rocks Rolls Rattler test_- Page. 236 27, 28, 30, 34 89 136 S. Saltillo. 202 Sandstone ___ 25 Sand__ 24 Sardis 223 Schist 28 Scoriae 28 Scott Co 230 Screening. _ 93—95 Screens..------ 93 Sedimentary rocks 32 Selma chalk 158-159 Selection of timber 86 Senatobia 234 Serrations in brick 151 Shrinkage of clay 162 Shale 26 Selenite 53 Silica 47-51 Size of Mississippi brick 139 Slate 28 Slaking 67 Soak pit 93 Soft-mud process _ 99 Specific gravity 65 Subcarboniferous 154-155 Success Brick and Tile Co 203 Sunflower County 232 Starkville.. 218 Stoneware clay 40 Stiff-mud process 99 Syenite.'. 28 T. Taste of clay 67 Tate County--. 234 Taylor Brick Co_--_- 191 • Tanner Brick Co 240 Tempering 95-97 Tensile strength 77-80 Tertiary period — 160 Terra cotta 40 Till - 27,33 INDEX. 255 Page. Tile clay 40 Tippah County 235 Thrasher 227 Thornton Brick Co 241 Tubbs Brick Co 212 Tunica County- - _ 236 Turkett 226 Tuscaloosa formation 155 Tufa 27 Transportation of clay 85-89 Travertine 27 Trachite 28 Tripoli 154 U. Union Brick and Tile Co 239 County 237 V. Van Hise, cited 219 Varieties of brick. 141 Vicksburg _240, 163 Verona. _ 202 W. Page. Wahalak 197 Wall white... 147 Warped brick 144 Warren County 239 Washington County 242 Water Valley 245 Webster County 244 Weight of brick 138 Welch-Trotter Brick Co 177 West Point 175 Whitney, cited--. 75 Wilcox stage .160, 161 Williams, cited. _ 76, 94, li2 Winona 210 Winston County. . 244 Wood 124 Y. Y alobusha County. .245 Yazoo City ... 247 County 246 ® Butler — '■“H, ^ L/y r ! Mississippi State Geological Survey ALBERT F. CRIDER, DIRECTOR. BULLETIN NO 3 THE LIGNITE OF MISSISSIPPI By CALVIN S. BROWN H i i l; i STATE GEOLOGICAL COMMISSION, His Excellency, James K. Vardaman Governor Dunbar Rowland Director of Archives and History A. A. Kincannon Chancellor of the State University J. C. Hardy President Agricultural and Mechanical College Joe N. Powers State Superintendent of Education GEOLOGICAL CORPS, Albert F. Crider. William N. Logan Calvin S. Brown . Director Assistant Geologist Assistant Geologist LETTER OF TRANSMITTAL. Jackson, Mississippi, July 20, 1907. To His Excellency, Governor James K. Vardaman, Chairman , and Members of the Geological Commission: Gentlemen — I submit herewith a report on the lignite of Mis- sissippi by Dr. Calvin S. Brown, and respectfully recommend its publication. Very respectfully, Albert F. Crider, Director. CONTENTS* PAGE Letter of transmittal 3 Contents 4 List of tables 7 Bibliography 8 Lignite in general 9 Definitions 9 Physical properties of lignite 10 Chemical properties of lignite 10 Origin of lignite 13 Geological age of lignite 13 Lignite of Mississippi 14 Field work 14 The lignite area of Mississippi 14 Topography of the lignite area 15 The geological formations of Mississippi 16 The Wilcox 19 Other lignite-bearing formations 21 The geological map 22 Mode of occurrence of lignite 22 Thickness of beds 24 Uncertainty of beds ; 24 Variation in quality 25 Some common errors 26 Burning beds 27 List of localities by counties 28 De Soto County 28 Marshall County 28 Benton County 28 Tippah County 29 Tate County 30 Panola County 30 Lafayette County 31 CONTENTS. 5 List of localities by counties — Continued. page Pontotoc County 34 Itawamba County 34 Monroe County 35 Calhoun County 35 Yalobusha County 37 Tallahatchie County 37 Webster County 38 Choctaw County 39 Winston County 40 Neshoba County 41 Kemper County 41 Lauderdale County 42 Jasper County 44 Rankin County 44 Hinds County 44 Claiborne County 45 Warren County 45 Yazoo County 46 Madison County 46 Scott County 46 Holmes County 47 Carroll County 50 Analyses of Mississippi lignite 51 vSamples and analyses 51 Interpretation of the table 52 Mississippi lignites compared with others 52 Worthless lignites 53 Moisture 54 Ash 55 Sulphur 56 Specific gravity 56 Analyses by Dr. Parr 57 Uses of lignite 58 General 58 In open grates 58 In stoves 58 In the forge 59 6 CONTENTS. Uses of lignite — Continued. page For burning brick 59 Under boilers 60 By briquetting . 62 By coking 63 For illuminating gas. . . , 63 For producer gas 63 For tar 66 For fertilizer 66 Acknowledgments 67 Index 68 Map after 71 LIST OF TABLES. PAGE 1. Ultimate analyses of coal and lignite 11 2. Comparative analyses of coal and lignite 12 3. The geological formations of Mississippi 16 4. Analyses of Wilcox clays 20 5. Analyses of Mississippi lignites 51 6. Comparative analyses of lignites 53 7. Analyses of inferior or worthless lignites 53 8. Moisture in fresh lignites 54 9. Analyses of ash from lignite 55 10. Specific gravity of lignites 56 11. Analyses of Mississippi lignites 57 12. Lignites tried in the forge 59 13. Analyses of clays associated with Holmes County lignites... . 60 14. Lignite test at Jamestown, North Dakota 61 15. Comparative tests of coal and lignite 61 16. Experiments in briquetting lignite 62 17. Comparative tests with boiler and gas-producer 64 18. Producer-gas tests of coals and lignites 64 19. Analyses of producer gas from lignites 66 BIBLIOGRAPHY. Wailes — Agriculture and Geology of Mississippi, 1854. Harper — Geology and Agriculture of Mississippi, 1857. Hilgard — Agriculture and Geology of Mississippi, 1860. McGee — The Lafayette Formation, Washington, 1892. Mabry — The Brown or Yellow Loam of North Mississippi, Journal of Geology, 1898. Shimek — The Loess of Natchez, Mississippi, American Geologist, 1902- Logan — Geology of Oktibbeha County, 1904. Logan — Preliminary Report on the Clays of Mississippi, 1905. Crider and Johnson — Underground-water Resources of Mississippi, U. S. G. S., W. S. 159, Washington, 1906. Crider — Geology and Mineral Resources of Mississippi, U. S. G. S., Bull. 283, Washington, 1906. Dumble — Brown Coal and Lignite of Texas, Austin, 1892. Burchard — Lignites of the Middle and Upper Missouri Valley, U. S. G. S., Bull. 225, Washington, 1903. Wilder — In Second Report of State Geological Survey of North Dakota, Bismarck, 1903. Wilder — In Third Report of State Geological Survey of North Dakota, Bismarck, 1904. Wilder — The Lignite of North Dakota, U. S. G. S., W. S. No. 117, Washington, 1905. Parker, Holmes and Campbell — Report on the Coal-testing Plant at St. Louis in 1904, U. S. G. S., P. P. 48, Washington, 1906. LIGNITE IN GENERAL. DEFINITIONS. I Lignite may be defined as immature coal or vegetable matter in the process of forming coal; it is a fuel intermediate in heating capacity between wood and coal. It belongs to a much more recent geological age than stone coal. Lignite is often mistaken for stone coal, especially when wet, but may be readily distinguished from it, even by the untrained observer, by noting the following differences. In general coal is black, whereas lignite is brown. When taken from water or when very moist, as many of the samples of Mississippi lignites are when first found, it appears rather black, but upon cutting with a knife exposes a brown surface; coal remains black when cut. When wet lignite is cut with a sharp knife it leaves a smooth surface or tends to do so, whereas coal when cut leaves a rough surface owing to its hardness and brittleness and tendency to fracture before the knife. Lignite upon drying cuts more like coal but is seldom as hard and compact. When a piece of dry lignite is put into water it gives out for some moments a characteristic crackling sound or click; this is not true of coal. The fracture of coal is bright and glossy, that of lignite usually dull. Lignite crumbles within a short time upon being exposed to the weather, whereas coal resists the influence of weather- ing much longer. Reports of the discovery of coal in Mississippi are of frequent occurrence in the newspapers, and in most cases have their origin in the discovery of lignite. If the finder would take the trouble in the future to compare his material carefully with a piece of coal before spreading reports, many errors would be avoided. If after the first comparison there is still doubt in his mind, let him place the coal and the lignite side by side in the sun for a few days and the difference will become apparent. No true coal has ever been found in Mis- sissippi, and judging from geological conditions there is little proba- bility that it will ever be found. There are within the lignite belts of Mississippi much lignitic clay and other lignitic earth. These contain more or less carbonaceous matter, but should not be confused with lignite. It is difficult of course to draw a hard and fast line between lignitic earth and earthy 10 LIGNITE. lignite; still none of these earthy materials should be called lignite which have not enough carbonaceous matter to enable them to bum readily under average conditions. Lignite is sometimes called brown coal. PHYSICAL PROPERTIES OF LIGNITE. In color lignite is brown or in the best qualities black, shading at times toward yellow and red; the streak and powder are usually brown. Its luster varies from dull to brilliant according to the composition and the impurities in it. Its texture also varies within wide limits; in the purer, better qualities it is hard, firm, and com- pact; in others it is soft; in others brittle. Some specimens tend to crumble upon exposure much more readily than others. In some specimens the woody texture is obliterated ; in others it is quite appar- ent ; in some instances pieces of wood are found but slightly altered ; in others pieces of logs completely silicified occur; and occasionally the same logs will be partly lignitized and partly petrified. Some samples of lignite show leaves, twigs, pine needles, and other small parts of plants. Lignite bums with both flame and smoke and gives off a disagreeable odor in the process. It does not fuse or cake upon burning, hence is not ordinarily available for making coke. Owing to the amount of earthy impurities the percentage of ash left after burning is frequently high. The specific gravity of lignite is usually less than that of bituminous coal and anthracite; sometimes, however, it is as high as that of bituminous coal* owing to earthy impurities contained. Roughly speaking we may put the specific gravity of lignite at 1 .2 to 1 . 5. • The fracture of lignite in some of the harder varieties is conchoidal, in other varieties it is irregular; in some the lignite tends to block in vertical lines, and it often has planes of cleavage parallel to the stratification ; in the woody types there is cleavage parallel to the grain of the wood. Most lignites have the capacity of absorbing a large amount of moisture and when first mined the percentage may be as high as thirty-five or even fifty. When exposed to the air this moisture evaporates in part, as a result of which the lignite tends to disintegrate. CHEMICAL PROPERTIES OF LIGNITE. Coal and lignite are composed of carbon, hydrogen, oxygen, and nitrogen, the principal element being carbon. In addition to these CHEMICAL PROPERTIES. 11 elements there are usually present as impurities sulphur and earthy matter. This earthy matter remains behind upon burning in the form of ashes. The following ultimate analyses of air-dried samples made by the St. Louis Coal -testing Plant of the United States Geo- logical Survey in 1904 give an idea of the relative proportion of these constituents in bituminous coal and lignites: TABLE 1. ULTIMATE ANALYSES OF COAL AND LIGNITE. (By U. S. Geol. Survey.) No. Kind Locality C H 0 N 5 Ash Total B. T. U. 1 Bituminous coal.. Bonanza, Ark. . . . 80.03 4.13 3.20 1.40 1.90 9.34 100 13,961 2 Bituminous coal. . Kentucky 78.31 5.36 8.80 1.85 1.2£ 4.44 100 14,319 3 Bituminous coal. . Carbon Hill, Ala. . 69.24 4.79 10.87 1.55 1.02 12.53 100 12,449 4 Rlark lignite Wyoming 58.41 6.09 28.99 1.09 .63 4.79 100 10,355 5 Brown lignite .... Texas 57.31 5.28 25.83 1.06 .71 9.81 100 9,904 6 Brown lignite .... North Dakota. . . . 55.16 5.61 30.98 .91 .63 6.71 100 9,491 It will be observed from the preceding table that in a general way the heating or calorific value (B. T. U., British thermal units) is pro- portional to the amount of carbon contained in the coal or lignite. It will be observed however that the Kentucky coal has a higher heating capacity than the Arkansas coal, although the latter has a slightly higher percentage of carbon ; this is due to the large amount of ash or inert matter which the Arkansas coal contains. The oxygen in coal and lignite adds nothing to its value, as might be supposed at first thought, for the air furnishes all the oxygen needed for com- bustion; furthermore the part of the oxygen contained in the water (H 2 0) is a positive disadvantage to the coal or lignite, as the water must absorb some of the heat in the process of vaporization. Instead, however, of the method of ultimate analysis shown above, proximate analysis is usually employed for coal and lignite, as it shows the amount of fixed carbon and volatile matter (combustible constituents) and of water and ash (non-combustible constituents). It should be remembered, however, that not all volatile matter is combustible, especially in lignite. The following table of proximate analyses made on an air-dried basis will show the position of lignite as compared with other fuels: 12 LIGNITE. Q £ < ►J o <£ in • 8 § " 8 Ld O ai 3 C/2 g CQ W *G < £ s H 3 I 3 S H > < Pi < a, -S e •8 v £r« I JU JD JD T 3 a a & & g a a ^ SSI-M*! w > > rt < < c/2 m co ID K ^ c/ 3 ^Wb>^t> Ol IO Ol Ol H H 00 ^ O l> w . N . t °. O. T*l' CO - . 2 .£ o w 8 gfg g fc £ § 3 § r - •§ a g* p 3 H(Sg. „ x *° o-l ■S 32 o 5 -£ a^^- C O w H V" V-i O * 3 S 3 to « J§ SfflcoSoQo II < H o o A TO o t* £ t/> to t/) CO 3 3 3 3 OOOO C 3 C C S 2 g g/g |555SS 1 1 I I I I g g | 6 £ |Q CO N 00 O) O H ORIGIN OF LIGNITE. 13 ORIGIN OF LIGNITE* Lignite, like coal, is of vegetable origin. The process of formation of these fuels seems to be briefly as follows : vegetable matter accum- ulated to considerable thickness; this was then covered by water or earth, and ultimately by earth alone; chemical changes gradually took place by which oxygen was lost and the relative proportion of carbon increased; along with this, due to these chemical changes, to pressure, and perhaps to other causes, took place a considerable decrease in volume. The process of transformation was very slow and required vast geological ages for its completion. The various stages of this change may be seen in peat, lignite, bituminous coal, and anthracite, the transformation being least in peat and greatest in anthracite. In the lignites the vegetable structure is often still plainly visible, pine needles, small parts of plants, woody branches and trunks being frequently found. The woody matter occurs in all stages of transformation from simple wood to completely lignitized matter. Side by side in the same bed of lignite may occur a trunk of but slightly altered wood and a trunk of petrified (silicified) wood containing enough carbonaceous matter to make it brown or black. Indeed the same trunk is sometimes partly lignitized and partly silicified. The clay associated with lignite often contains well defined leaf and plant impressions. GEOLOGICAL AGE OF LIGNITE, It has already been said that lignite is of a later geological age than true coal. The true coals, that is anthracite and bituminous coal, belong principally to the Carboniferous Age (Paleozoic Era). Coal is also found in the Triassic and the Jurassic periods (Mesozoic Era). The black lignites or subbituminous coals of Colorado, New Mexico and Wyoming, and the brown lignites of North Dakota are found in the Cretaceous (late Mesozoic). The brown lignites of Texas belong to the Tertiary (Cenozoic Era). By far the greater part of the brown lignites of Mississippi, Alabama and Tennessee belong also to the Tertiary; some deposits, however, are found in the Cretaceous. LIGNITE OF MISSISSIPPI, FIELD WORK* The field work for this report was begun on the 15th of June and finished on the 5th of September, 1906. During this time I visited all the localities in the State in which lignite had been reported to exist and brought to light many outcrops of which no written record existed. I examined in all about two hundred outcrops of lignite and took samples of fifty of the most promising of these. While I tried to visit every county and locality in which lignite was thought to exist, I found it impossible during the one summer at my command to inspect every individual outcrop of lignite reported to me in some of the districts where such outcrops are of frequent occurrence. In such cases I tried always to choose the best or most representative deposits for examination. Very few of these deposits have ever been worked or opened with a view to commercial use. Many occur in or near the bottom of creeks and ravines and others in private springs. Hence in many instances it was found impossible to make as complete an examination as was desirable without the expenditure of more time and money than were at my disposal. It resulted in many cases that instead of taking samples throughout the vertical extent of the beds I was forced to take them from the top or the first ten or twelve inches of the bed, or from the most accessible point. Nor was I always able to measure the thickness of the strata, for the frequent presence of iron pyrite in the lignite made it impossible to use the extension auger in many instances. THE LIGNITE AREA OF MISSISSIPPI. The lignite area of Mississippi is that part of the State lying north of a line through Meridian, Jackson and Vicksburg, and east of the “Bluff.” A few outcrops of lignite are found south of this limit, but they belong to later geological formations and are relatively infrequent and unimportant. The Bluff here mentioned is part of that line of bluff extending from Kentucky to Louisiana east of the Mississippi TOPOGRAPHY. 15 River and parallel with it. Between Memphis and Vicksburg the river is deflected from the Bluff, leaving between the river and the bluff the low level country known as the “Delta.” No lignite is found west of this line of Bluff in Mississippi. The lignite area on the map published by the United States Geological Survey in the first volume of the Report on the Coal-test- ing Plant of St. Louis (P.P. No. 48) should be greatly extended — on the west to the line of the bluff, and on the north far into Tennessee. Under the heads of Geological Formations, Distribution in Missis- sippi, and List of Localities, more detailed information will be given on the subject of the lignite area in Mississippi. TOPOGRAPHY OF THE LIGNITE AREA. The north-central area of the State, in which the lignite occurs, is characterized by a rough, hilly surface frequently cut by deep gullies. Along the larger streams the process of erosion has gone on until the valleys are several miles wide. A large part of the material on the surface or near the surface being sand, erosion is still going on rapidly in the hills and uplands. Much of the sand and earth thus washed down is redeposited along the streams and valleys. Consequently the surface of the country is changing constantly and rapidly. The elevation of the territory is nowhere great. The following railroad elevations, taken from Gannett’s “Dictionary of Altitudes,” will indicate the general range: Railroad Elevations. Feet. 1 . Lexington 209 2. West 290 3. Louisville 536 4. Ackerman 522 5. Coffeeville 241 6. Oxford 458 7. Holly Springs 602 8. Olive Branch 387 9. Hernando 391 10. Sardis 384 Holly Springs is the only railroad town in the State with an eleva- tion above 600 feet. A point on the Illinois Central Railroad about 1£ miles south of Holly Springs (between mile posts 544 and 545) has 16 LIGNITE. an elevation of 619 feet-; this is the highest railroad point in the State. It is therefore doubtful if there are many hi 11 -tops which exceed 700 feet. On the other hand the Delta lying west of the lignitic area and through which much of the latter is drained has an average elevation of about 150 feet; so that 200 feet may be taken as approximately the lower altitude limit of the lignitic area. Thus it is seen that the elevation of this territory ranges between 200 and 650 or 700 feet, a range which is not very great, and yet which is sufficient to give con- siderable inequality and diversity to the landscape. In fact, the character of the two upper geological strata are such that the resulting topography may in many places be called rugged. THE GEOLOGICAL FORMATIONS OF MISSISSIPPI. The nomenclature of the geological formations of Mississippi, as adopted by the present geological survey, is as follows: Cenozoic. Mesozoic , Paleozoic. TABLE 3. THE GEOLOGICAL FORMATIONS OF MISSISSIPPI. f Quartemary. f River alluvium. I Yellow loam. Loess. Port Hudson. Lafayette. Miocene (?).... Grand Gulf. Miocene Pascagoula. Oligocene Vicksburg. Tertiary. f Eocene. Cretaceous. ( Jackson. f Lisbon and undifferen- Claibome