UNIVERSITY OF ILLINOIS LIBRARY class 551 Book Volume '>vcro.^S5‘-5^ Mr 10-20 M geology DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS' SMITH, DIRECTOR BULLETINS Nos. 355-359 WASHINGTON GOVERNMENT PRINTING OFFICE I SCO Digitized by the Internet Archive in 2016 https://archive.org/details/magnesitedeposit3553hess CONTENTS Geological Survey, bulletin 355; Magnesite deposits of California. Same 356; Geology of Great Falls coal field, Mont. Same 357; Preliminary report on Coalinga oil district, Cal. Same 358; Geology of Seward Peninsula tin deposits, Alaska. Same 359; Magnetite deposites of Cornwall type in Pennsylvania. 4 169054 DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, Director Bulletin 355 THE MAGNESITE DEPOSITS OF CALIFORNIA BY FRANK L. HESS WASHINGTON GOVERNMENT PRINTING OFFICE 1908 CONTENTS. Page. General remarks 7 Introduction 7 Composition, properties, and uses 8 General character 8 Manufacture and use of carbon dioxide 8 Calcination of magnesite 9 Magnesia brick, shapes, and crucibles 11 Magnesium carbonates 13 Oxychloride cement 13 Other uses 14 Market for California magnesite , v 15 Production 16 Imports of magnesite and its products 16 Description of deposits 17 General statement 17 The Coast Range occurrences 21 Mendocino County 21 Hixon ranch deposits 21 Sonoma County 1 22 Creon deposit 22 Eckert ranch deposits 23 George Hall ranch deposit „ 24 Pat Cummings claim 24 Gilliam Creek deposits 24 Madeira deposit 25 Unnamed deposit 25 Red Slide deposits 26 Norton ranch deposits 28 Napa County 28 General remarks 28 Walters or White Rock deposit 28 Snowflake and Blanco claims 29 Priest deposit 31 Russell deposit 31 Matthai deposits 31 Santa Clara County 31 Deposits near Coyote 31 Bay Cities Water Company’s land 32 Mrs. A. F. Cochrane’s land 33 Red Mountain deposits . . 33 Other Santa Clara County deposits 37 Alameda County 37 King claim 37 Banta’s camp deposit ., 37 Stanislaus County 37 San Benito County 38 3 4 CONTENTS. Description of deposits — Continued. The Coast Range occurrences — Continued. Page. San Luis Obispo County 38 Santa Barbara County 38 Riverside County 38 The Sierra Nevada occurrences 39 Kern County 39 Tulare County 39 White River deposits 39 Deer Creek deposits 39 Porterville deposits 39 Deposits on South Fork of Tule River 46 Round Valley deposits 48 Deposits near Exeter 49 Naranjo deposits 49 Other Tulare County deposits.. 49 Fresno County 50 Mariposa and Tuolumne counties 51 Placer County 52 Magnesite deposits in other countries 52 North America 53 Canada 53 Quebec 53 British Columbia 53 Mexico 54 Lower California 54 South America 55 Venezuela 55 Europe 55 Austria 55 Hungary 56 Germany 56 Greece : 57 Italy 58 Macedonia 58 Norway 59 Russia 60 Africa 60 Transvaal 60 Other African deposits 61 Asia 61 India 61 Madras 61 Mysore 61 Ceylon 61 Australia 62 Queensland 62 New South Wales 62 South Australia 62 Tasmania 62 Oceania 63 New Caledonia 63 Index 65 ILLUSTRATIONS. Page. Plate I. Map of California, showing distribution of magnesite deposits II. Specimens of magnesite, showing conchoidal fracture 8 III. Weathered surfaces of magnesite 18 IV. A, Small irregular vein of magnesite in serpentine; B, Magnesite weathered under several inches of clay 20 V. A, Outcrop of magnesite on Hixon ranch, Mendocino County; B, Entrance to lower tunnel on Sonoma Magnesite Company’s claim, near Cazadero; C, Outcrop of magnesite vein on Walters claim, Pope Valley 20 VI. Cracks in magnesite apparently due to shrinkage: A, Compact magnesite from the Hixon ranch, Mendocino County; B , Less compact magnesite coated with a thin layer of quartz, also cracked, from locality 4 miles northeast of Porterville 22 VII. Structure of magnesite on Bay Cities Water Company’s land on Coyote Creek: A, Specimen from the upper deposit, showing a natural surface; B, Specimen from the lower deposit, showing a smoothly ground surface 32 VIII. A, Stockwork of magnesite veins miles south of Winchester; B, Sheeted serpentine containing many thin veins of magnesite near Deer Creek, Tulare County 38 IX. A, Amphibolite dike cutting through flat vein of magnesite; B, Crushed magnesite vein near Porterville, 40 X. Northern hill at the Willamette Pulp and Paper Company’s mag- nesite mine near Porterville: A, Nearly vertical vein; B, Lower ‘ 1 blanket ’ ’ vein 42 XI. A, Outcrop of stockwork of veins at north end of Willamette Pulp and . Paper Company’s deposits near Porterville; B , Furnace for calcin- ing magnesite at Willamette Pulp and Paper Company’s magnesite mine near Porterville 44 XII. A, Magnesite vein on south side of Kings River, 9 miles east of Sanger, Cal. ; B, Magnesite vein on Snow Cap claim, north side of Kings River, 9 miles east of Sanger 50 Fig. 1. Diagram of Western Carbonic Acid Company’s plant at Sedan, Cal 9 2. Plan of magnesite veins and workings 4 miles northeast of Porter- ville, Cal 42 3. Diagram showing mode of working a highly inclined magnesite vein at Willamette Pulp and Paper Company’s mine near Porterville, Cal . 44 4. Elevation and plan of Willamette Pulp and Paper Company’s furnace, 4 miles northeast of Porterville, Cal 45 o . ■ MAP OF CALIFORNIA, SHOWING DISTRIBUTION OF MAGNESITE DEPOSITS (•). THE MAGNESITE DEPOSITS OF CALIFORNIA, By Frank L. Hess. GENERAL REMARKS. INTRODUCTION. Magnesite, or magnesium carbonate, ordinarily occurs in veins or in masses replacing other rocks rich in magnesia, though it seems probable that a few isolated and impure deposits in Quebec are of sedimentary origin. (See p. 53.) Although it can hardly be classed as a common mineral, it exists in comparatively large deposits at many places in various parts of the world. The principal foreign deposits now worked are in Austria, Greece, India, Italy, Norway, Russia, and South Africa. Other deposits which are either not worked or from which the output is small occur in Africa, Australia, British Columbia, Lapland, Mexico, Quebec, and* Venezuela. In the United States the only important deposits known are in California. Small veins of miner alogic interest only have been noted in Pennsylvania,® Maryland, 6 and Massachusetts, 0 and veins of unknown extent are reported to exist in Nevada and Arizona. The Maryland and Pennsylvania deposits were at one time worked in a small way, the product being used for making Epsom salts (magnesium sulphate) and other chemicals, but magnesite from Austria, Greece, and South Africa can now be imported so cheaply that it no longer pays to operate them. In California the deposits are scattered along the Coast Range from Mendocino County, and possibly farther north, to a point south of Los Angeles, and along the western slope of the Sierra Nevada from Placer County to Kern County. (See PI. I.) Deposits are worked in Sonoma County near Cloverdale, in Santa Clara County near Livermore, and in Tulare County near Porterville. Mines were formerly operated in Chiles and Pope valleys, Napa County, and a Frazier, P., jr., Lancaster County: Second Geol. Survey Pennsylvania, Vol. CCC, 1880, pp. 89, 97, 176-179, 196. b Bascom, F., The geology of the crystalline rocks of Cecil County : Cecil County report, Maryland Geol. Survey, 1902, pp. 96-97. c Dana, J, D., A system of mineralogy, 6th ed., 1892, p. 275. 7 8 MAGNESITE DEPOSITS OF CALIFORNIA. considerable prospecting and preparatory work has been done at several other places with desultory production. The field work on which the present article is based was done in November, 1905, and during the winter of 1906-7. The literature of magnesite deposits is scanty, and aside from paragraphs and short general articles appearing in current periodicals from time to time, but little has been published on the California magnesite deposits. COMPOSITION, PROPERTIES, AND USES. GENERAL CHARACTER. Magnesite is a carbonate of magnesium (MgC0 3 ), having, accord- ing to Dana, a a specific gravity of 3 to 3.12, and a hardness of 3.5 to 4.5. It is somewhat heavier than cal cite (2.714 specific gravity), and is about one-third harder, the hardness of calcite being 3. It contains 52.4 per cent of carbon dioxide (C0 3 ) and 47.6 per cent of magnesia (MgO). As it occurs in the California deposits, magnesite when compara- tively pure is ordinarily a beautiful, white, fine-grained rock, with a conchoidal fracture that looks like a break in china. (See PI. II.) It will take a fine polish and when so treated is an opaque white. Locally a portion of the magnesite occurs in a fine powder in what seem to be decomposition cavities and upon surfaces exposed to weathering. MANUFACTURE AND USE OF CARBON DIOXIDE. Magnesite gives off carbon dioxide on strong heating and is used in preference to limestone for the production of this gas, as it contains a much greater proportion than calcium carbonate, which carries but 44 per cent. Other advantages of magnesite are that the residual magnesia left after calcination is more valuable than lime, and that the amount of heat required to drive off the carbon dioxide is much less. Considerable. amounts of liquid carbon dioxide are manufactured in Oakland from magnesite. As made at the Western Carbonic Acid Gas Company’s plant at Sedan (Emeryville post-office), a suburb of Oakland, the magnesite is fed into a kiln with about one-tenth its weight of coke, and the gas from the combustion of the coke, together with that driven off from the magnesite, is pumped into scrubbers, of which there are three, filled with broken limestone to counteract any sulphuric acid, and washed with sea water. The use of sea water rather than fresh water is merely an economy. The gas then passes to an absorption tower where it comes into contact with a sprayed solution a Dana, J. D., A system of mineralogy, 6th ed., 1892, p, 274. U. S. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. II B SPECIMENS OF MAGNESITE SHOWING CONCHOIDAL FRACTURE. A, From vicinity of Success schoolhouse, 8 miles east of Porterville; B, From Red Mountain, Santa Clara County. Natural size. COMPOSITION, PROPERTIES, AND USES OF MAGNESITE. 9 of potassium carbonate, by which it is absorbed. The ‘ ‘loaded solution ” is then pumped into boilers where it is raised to a temperature just below the boiling point of wa- ter. The solution gives up its gas and is pumped back to the absorption tower for another load, while the gas is pumped through cleansing tanks and cooling pipes to a gasometer. It is then liquefied by a three- step compressor and run into steel cylinders, holding 25 to 60 pounds each, for shipment. In this process the weight of gas obtained is about 50 per cent of the weight of the mag- nesite used. The accompany- ing diagram (fig. 1) will proba- bly make the steps clear. The gas is shipped throughout the Pacific coast and Southwest- ern States. It is used in re- frigeration and in making soda water and other carbonated beverages. The magnesia left as a residue is shipped to paper mills in Oregon, where it is used, after being changed to a sulphite, in the digestion and whitening of wood pulp for pa- per. This is the chief use to which California magnesite is put, and almost the entire out- put of the Porterville deposits eventually finds its way to these mills. CALCINATION OF MAGNESITE. Among men engaged in cal- cining magnesite, a difference of opinion has existed as to the temperature at which the car- 10 MAGNESITE DEPOSITS OF CALIFORNIA. bon dioxide can be driven off. In recent experiments Otto Brill® has determined this point and made a number of interesting discoveries as to the behavior of magnesite when heated. His experiments were carried on with small amounts of carefully prepared and purified mate- rials, so that his results are not exactly analogous to those that would be obtained by using the raw natural material. He showed that calcium carbonate (as ordinary limestone) gives, up all of its carbon dioxide at 825° C. (1,517° F.), but that magnesium carbonate (magnesite) begins to give off carbon dioxide at about 237° C. (465° F.). A cer- tain quantity is given off at this temperature, after which little or none is exhaled until the magnesite is heated to 250° C. (482° F.), at which point another certain quantity escapes. On raising the temperature a third partial dissociation point is reached at 265° C. (509° F.). Other such stages were marked at various points, and these were considered to show the successive formation and break- ing up of various basic carbonates. The last of the carbon dioxide is given off at 510° C. (950° F.), a temperature much below that needed to calcine limestone. Brill’s table showing the different car- bonates formed is given below. The reduction to the Fahrenheit measurement of temperature is added by the writer of this paper. Basic carbonates formed in burning magnesite. Calcu- lated MgO. Obtained MgO. Dissociation tem- perature. 10MgO,9CO 2 Per cent. 50.64 Per cent. 50.58 °C. 265 °F. 509 9MgO, 8C0 2 50. 79 50. 98 295 563 8Mg0,7C0 2 51.20 51.37 325 617 7MgO, 6C0 2 51.51 • 51. 69 340 644 6MgO, 5C0 2 52. 36 52. 35 380 716 5MgO, 4C0 2 53. 41 53.03 405 761 7MgO, C0 2 86.53 86. 31 510 950 The temperature at which magnesite gives up the last of its carbon dioxide, 510° C., is below a red heat, but the time required to drive off all of the gas is not stated by Brill, and this, of course, would vary with the size of the material used. The important point, however, is that at this temperature all of the carbon dioxide will be driven off, so that, although higher heating will undoubtedly remove the gas more quickly, because the heat will reach the inner portions of frag- ments sooner, it ordinarily means a waste of fuel. After magnesite is calcined the resultant magnesia takes up C0 2 from the air, again returning to the form of magnesite or magnesium carbonate, but it does this so slowly that it can not compete with lime or hard plasters in structural work. oUeber die Dissoziation der Karbonate der Erdalkalien and des Magnesiumkarbonates: Zeitschr. anorg. Chemie, vol. 45, part 3, June, 1905, pp. 277-292. COMPOSITION, PROPERTIES, AND USES OF MAGNESITE. 11 MAGNESIA BRICK, SHAPES, AND CRUCIBLES. Calcined magnesite (magnesia) is used 'for making refractory brick and shapes for furnace linings. These products will stand exceed- ingly high temperatures, above any heat that can be obtained in re- generative furnaces, so that they are much used for lining electric furnaces. A considerable number are also employed in cement kilns and fire boxes for burning crude oil, uses in which intense and long- continued heat must be endured. They are also exceedingly resist- ant to corrosion by basic slags and most molten metals. These qu ah ties make them desirable for linings in furnaces used for copper smelting and in the manufacture of basic steel. In the latter proc- ess the lime added to remove phosphorus and silica attacks clay or silica fire brick severely, but magnesia brick are little affected. Furnaces built of magnesia brick or shapes must, to prevent crack- ing, be heated evenly and as gradually as possible, so that the inner ends will not be raised to a high temperature while the outer portions are still cold. The same care must be used in cooling off, and the furnace must lose its heat gradually and evenly if the shapes are to be preserved. Sometimes considerable trouble is caused by the swell- ing of magnesia brick and shapes on heating and a corresponding shrinkage on cooling, and copper converters are reported to have burst from this cause. This difficulty seems to be due largely to insufficient sintering, for very strongly sintered brick are said to give little trouble. A plant for the manufacture of magnesia brick was erected at Clinton, a suburb of Oakland, in 1905, and is still in operation. Most of the magnesia brick made in this country are manufactured from European magnesite. Some magnesia brick of foreign manu- facture were formerly imported each year, but none are shown in the customs returns for 1907. Magnesia crucibles are made of various forms and different de- grees of fineness. Crucibles made from pure magnesia have much the appearance of fine biscuit ware. If heated to incipient melting they have the appearance of translucent glass. When the ordinary European commercial calcined magnesite is used for crucibles, it has little strength above a red heat, but crushes in the tongs like so much putty.® Dr. Oliver P. Watts, in a long series of experiments in the preparation of metallic alloys, used magnesia crucibles as finings for carbon or graphite crucibles to prevent the absorption of carbon by the charge, and found that they answered the purpose excellently. In such crucibles alloys of iron with aluminum, cobalt, chromium, copper, manganese, molybdenum, nickel, silicon, silver, tin, titanium, o Watts, Oliver P., in letter to author. 12 MAGNESITE DEPOSITS OF CALIFORNIA. and tungsten were made. Chromium, silicon, and titanium, when forming 10 per cent or more of the charge, seemed to attack the linings, to judge from the failure of a number of them. 11 These linings are extremely refractory, so that the maximum temperature at which they can be used is fixed not by their melting, but by another phenomenon, the reduction of the magnesia by car- bon.”® The carbon attacks the magnesia and corrodes it, especially if iron oxide be present, in which case, under very high temperatures, the iron oxide is volatilized and, coming into contact with the graph- ite crucible, is reduced and collects as microscopic spheres of iron. These grow and roll down the sides, carrying absorbed graphite, which vigorously attacks the magnesia after the equation MgO + C = Mg + CO. At a lower temperature this action is reversed, and for this reason magnesium can not be obtained from magnesia by reduc- tion with carbon. Magnesia crucibles made under such temperatures are white, even when much iron oxide is present in the raw materials, for the iron oxide is volatilized and driven out. 6 Mr. A. J. Fitzgerald, of Fitz- gerald & Bennie, Niagara Falls, N. Y., states in a letter of March 21, 1908, to the writer, that his firm melts charges of 6 or 7 pounds of alloys in magnesia crucibles in electric furnaces by withdrawing the charge through the bottom. Cracking from change of temperature is not likely to take place in small, well-fused magnesia crucibles. Much mystery has been attached to the binders used in making magnesia brick, shapes, and crucibles, to cement the particles together when burned. It is a common belief among persons handling magnesite that to make brick which will hold together when burned it is necessary to use magnesite containing impurities consisting of iron oxides or serpentine. It is undoubtedly true that such impurities will allow the sintering of brick at very much lower temperatures than are necessary with pure magnesite, but they also make the brick more fusible and more easily corroded by molten materials. A pure magnesia brick demands a very high temperature for sintering, but bricks can be made without the impurities mentioned or others, and when so made are extremely refractory. Dead-burned magnesite — that is, magnesite from which the C0 2 has been entirely driven off — has little or no plasticity, so that it is hard to handle. It is said that its plasticity is much improved by using partly calcined or caus- tic magnesite with it. Heavy pressure will bind the material suffi- ciently to allow it to be sintered; 240 tons per brick is used in the works at Snarum, Norway. 0 a Letter cited. See also paper by Doctor Watts, The action of carbon on magnesia at high tempera- tures; Trans. Am. Electrochem. Soc., vol. 10, 1907, pp. 279-289. i> Watts, O. P., op. cit., p. 287. c Daumann, E., Magnesit fran Snarum: Bihang till Jem-Kontorets Annaler for 1905, Stockholm, 1905, pp. 222-225. COMPOSITION, PROPERTIES, AND USES OF MAGNESITE. 13 Magnesia may be melted to a glassy substance in an electric furnace, but when so treated contains many bubbles. It seems highly prob- able that it would be profitable to sinter magnesia brick and similar products in an electric furnace, where electric power is as plentiful as it is in California. MAGNESIUM CARBONATES. For some of the purposes to which magnesite is rather extensively put, dolomite, the calcium magnesium carbonate, may be used, as in the making of magnesia alba levis (light magnesium carbonate) and Epsom salts. The light carbonate is well known as a toilet prepara- tion and is also used in medicine. Mixed with various amounts of asbestos it is used for pipe covering and boiler lagging; 85 per cent of light carbonate to 15 per cent of asbestos is a common proportion. The asbestos is needed to hold the powdery carbonate together. For this purpose water glass (sodium silicate) is also sometimes added to the mixture. The heavy carbonate is sometimes used instead of the light carbonate, in which case the efficiency of the covering is probably diminished owing to the lesser degree of porosity. The light carbonate is said to make an excellent absorbent for dyna- mite manufacture, as it does not readily allow the nitroglycerine to “ sweat” out. Powdered magnesite is introduced to prevent scale in boilers in which sulphurous waters are used, as the magnesium sul- phate (Epsom salts) formed is highly soluble. OXYCHLORIDE CEMENT. For many years it has been well known that a moistened mixture of magnesium oxide (magnesia) and magnesium chloride will form an exceedingly strong cement, and numerous attempts have been made to use it in manufacturing tiles, artificial stone, flooring, wainscoting, etc. Many of these attempts have met with failure owing to an unlooked-for decomposition of the manufactured product, and this has prevented the industry from becoming important as quickly as had been expected. The failure of the cement seems to be due to the presence of lime either in the magnesium chloride or in the mag- nesia, which in the form of chloride is hygroscopic and by taking up water swells and destroys the usefulness of the material, and so where magnesite is to be used in the manufacture of cement efforts are made to obtain it as free from lime as possible. At the Malelane deposits, South Africa, the magnesite is calcined,, ground, and mixed with imported German magnesium chloride at the mine and shipped ready for use as cement.® In using the cement for flooring, wainscoting, etc., it is mixed with sawdust or sand and coloring matter to give it the desired tint. It ° Hall, A. L., The magnesite deposits of Malelane: Rept. Geol. Survey, Transvaal Mines Dept., 1906, Pretoria, 1907, pp. 127-132, 14 MAGNESITE DEPOSITS OF CALIFORNIA. may be laid in a continuous sheet over considerable areas and is said to crack much less easily than cement. The use of sawdust- makes the material very much lighter in weight than cement, less hard, and more resilient. The surface is commonly waxed and polished, like a wooden floor. At the present time a large part of the Grecian magnesite imported into this country is used for making such floors. The material has also been used for wall plaster, and in speci- mens seen by the writer would stand severe abuse without breaking. In these preparations the sawdust particles are well separated, so that the material is in a high degree fireproof. The same mixture is used for making stationary washtubs and for similar purposes. OTHER USES. Sintered magnesite tubing of assorted sizes, up to 31.5 inches in length and 2.8 inches in diameter, is regularly made for chemical and electrometallurgical work. The fusing point of magnesia has been determined by Goodwin and Mailey® as about 1910° C. The same experimenters found that the fused material is not acted upon by fused silver, sodium, potassium, or barium nitrates ; nor by sodium, potassium, or zinc chlorides, bro- mides, or sulphate, even after an hour’s exposure of a polished surface to their action. Barium chloride has a very slight action on it, but sodium carbonate, potassium sodium carbonate, potassium hydrate, and cryolite attacked the fused oxide energetically. Cold dilute hydro- chloric, nitric, and sulphuric acids attack the fused oxide slowly, and concentrated acids are less active than dilute acids . b The fused mag- nesite takes up but little C0 2 from the air, and it is possible that if pure material were used it would be found that there is no recombi- nation with carbon dioxide. In experiments performed by Fitz- gerald & Bennie, 0 during which they found specimens to take up 0.42 and 0.63 per cent C0 2 , the magnesia used contained 1.10 and 2.48 per cent of lime, respectively, which may have been the com- bining substance. According to the experiments of Goodwin and Mailey the coefficient of linear expansion of fused magnesia is almost the same as that of platinum, and but little more than that of quartz parallel to the optic axis. They find the coefficient of linear expan- sion between 120° and 270° C. to be— a t = 10" 8 [1140 + 0.92 (*-120°)], while for platinum they quote Holborn and Day as giving — a t = (8889 + 1.274 t) 10' 9 for * = 0° to 1000°. a Physical properties of fused magnesium oxide: Trans. Am. Electrochem. Soc., vol. 9, 1906, pp. 92-93. b Op. cit., p. 98. c Discussion of “Physical properties of fused magnesium oxide:” Trans. Am. Electrochem. Soc. vol. 9, 1906, pp. 101-103, MARKET FOR CALIFORNIA MAGNESITE. 15 In these formulae a t stands for the coefficient of expansion at any given temperature, t standing for temperature. A coating of crushed magnesite is laid on hearths used for heating steel stock for rolling, to prevent the scale formed from attacking the fire brick of the hearth. When heated to a high degree magnesia becomes incandescent like lime and the rare-earth oxides. On account of this property numer- ous efforts have been made to construct an incandescent lamp, similar to the Nernst lamp, which uses a glower made of zirconia and yttria, but not much success has been attained. A patent® has been taken out for the construction of electrodes for arc lamps from a mixture containing 90 per cent of magnesia and 10 per cent of iron oxide. Magnesia is a poor conductor of electricity, 6 and the iron oxide is introduced to increase the conductivity. Owing to its nonconduc- tivity magnesite mixed with iron dust has been used for the manu- facture of rheostats. c Magnesia has been used for an adulterant in paint, but it has little virtue as a pigment. Its covering properties are poor, and it settles badly in the mixture. Magnesium (metal) is not obtained from magnesite, but from mag- nesium chloride, which is obtained in large quantities from the Stass- furt salt deposits in Germany and from sea water at other places. MARKET FOR CALIFORNIA MAGNESITE. The market for California magnesite is at present limited to the Pacific coast and Rocky Mountain States, as the necessarily high freight rates, due to the long railroad haul to the eastern portion of the country, preclude its shipment in competition with imported magnesite. Moreover, the California deposits are handicapped in the competition with foreign deposits by the much higher scale of wages paid in this country. Day laborers in California receive $1.50 to $2 for a ten-hour day, and if miners are hired for the work, $2.50 to $3 must be paid. In Hungary the wages paid in 1906 at the works of the Magnesite Company (Limited) were 40 cents per ten-hour day for common labor and 80 cents for foremen.** Besides these drawbacks, none of the California veins compare well in size with the reported width of the Hungarian veins. In quality, however, the comparison with the foreign material is favorable; in fact, the California article is ordinarily better. Magnesite from Porterville now costs about $6.50 per short ton laid down at San Francisco; probably that from the Gilliam Creek (Sonoma County) deposits can be delivered for somewhat less. Pro- a Lewis J. Jones, letters patent No. 484553, dated October, 1892. b The conductivity of magnesia when heated is treated in the article by Goodwin and Mailey, to which reference has been made (p. 14). c E. W. Gilbert, letters patent No. 439939, dated November 4, 1890. Private letter. 16 MAGNESITE DEPOSITS OF CALIFORNIA. duction at the Kings River deposits will cost about the same as at Porterville. Magnesite from Sonoma and Napa counties can prob- ably be calcined and laid down in San Francisco at $15 per short ton. Imported magnesite is now (April, 1908) quoted in New York City at $7.25 to $8 per long ton, equal to $6.38 to $7.08 per short ton; calcined magnesite is quoted at $16.75 to $25, and when compara- tively free from lime, ground, sells in small lots at the latter price. With this difference in price for calcined magnesite of about $5 to $6 between San Francisco and New York, it seems possible that this product could sometimes be shipped at a profit to the eastern coast of the United States on vessels that would otherwise sail without a full cargo and would for this reason be willing to carry the material at low rates. In spite of the fact that the California magnesite is ordinarily purer and cheaper, calcined Grecian magnesite is shipped into Los Angeles as “ white cement” for use in oxychloride cement. PRODUCTION. The production of magnesite in California since 1891, the first date for which figures are available, has been as follows : Quantity and value of crude magnesite produced in California , 1891-1907. a Short tons. Value. Short tons. Value. 1891 439 1,004 704 1,440 2,220 1,500 1,143 1,263 1,280 $4,390 10,040 7,040 10,240 17.000 11.000 13, 671 19,075 18, 480 1900 2,252 3,500 2,830 3, 744 2,850 3,933 7,805 b 7, 762 $19, 333 10, 500 8,490 10,595 9, 298 15, 221 23, 415 50, 453 1892 1901 1893 1902 1894 1903 1895 1904 1896 1905 1897 . 1906 1898 . 1907 1899 a Yale, C. G., Magnesite: Mineral Resources U S. for 1906, U. S. Geol. Survey, 1907. The figures for 1907 were also kindly furnished by Mr. Yale b From this amount 3,234 tons of calcined magnesite, worth $20 per ton, was produced. IMPORTS OF MAGNESITE AND ITS PRODUCTS. The imports of magnesite into the United States for the last three years have been as follows : Imports of magnesite and magnesite products into the United States in 1905, 1906, and 1907. a 1905. 1906. 1907. Pounds. Value. Pounds. Value. Pounds. Value. Magnesia: Calcined, medicinal Carbonate of, medicinal . . Sulphate of, or Epsom salts Magnesite: Calcined, not purified Crude 13, 554 21, 901 9,039,099 134,595,334 14, 152, 466 $2, 778 1,360 38,084 575,355 63,264 30, 788 39, 487 5,830,224 141,314,682 39, 477, 766 $5, 689 5,844 22, 471 740,585 122,908 49,489 85, 467 4,532, 713 151, 137, 661 46,878, 740 $9,005 3,994 16,256 688,371 186,988 a Figures furnished by Bureau of Statistics. GENERAL DESCRIPTION. 17 There is no duty on magnesite or calcined magnesite, nor on the salts of magnesium mentioned in the table. For some reason the cal- cined magnesite imported in 1907 is declared of much lower value than the market price ($8.11 per ton as compared with $16.75 to $25). DESCRIPTION OF DEPOSITS. GENERAL STATEMENT. The California magnesite deposits, so far as known, all occur as veins in connection with serpentinized magnesian rocks. By far the larger part are in the Coast Range, in the serpentinized rocks that stretch from southern California into Oregon. These rocks, although in few places wholly altered, will be referred to as serpentines, the name by which they are ordinarily known. Those in the Coast Range are probably lower Cretaceous in age a and cover large areas, Becker 6 estimating that between Clear Lake and New Idria, a distance of about 200 miles, there are more than 1,000 square miles of serpentine. Through a large part of this area magnesite veins of various sizes are found. Veins large enough to be more or less workable are known to occur at many places in Mendocino, Sonoma, Napa, Alameda, Stan- islaus, and Santa Clara counties. Along the western side of the Sierra Nevada magnesite is found in Placer, Fresno, Tulare, and Kern counties, and in southern California in Riverside County. The serpentines of the Coast Range are ordinarily greenish or bluish, greatly broken and faulted, a solid block a foot in diameter being a rarity in many localities. They are derived from olivine-pyroxene rocks, in which the amounts of the minerals vary in ratio at different localities. Here and there the rocks still carry considerable portions of only partly altered minerals, though the general decay is far advanced. There is great difference, both in the comparative amounts of the original minerals from which the serpentine is formed, and in the degree of serpen tinization, even in small areas. Some rocks are almost wholly made up of partially serpentinized olivine, in places carrying chromite and chromic mica, while near at hand other speci- mens show large quantities of orthorhombic pyroxene. Along the Sierra Nevada the serpentine at the Fresno and Tulare County locali- ties is of a dull drab or brown color and that in Tulare County is much less broken than the Coast Range serpentines. Magnesite is probably formed both from the breaking down of the serpentine-making minerals and from the serpentine itself. In a specimen from the northeast corner of Santa Clara County ensta.tite has been replaced by magnesite. Many of the cracks in the olivine are filled by magnesite. These cases seem to show the derivation of a Fairbanks, H. W., San Luis folio (No. 101), Geologic Atlas U. S., U. S. Geol. Survey, 1904, p. 6. b Becker, G. F., Geology of the quicksilver deposits of the Pacific slope: Mon. U. S. Geol. Survey, vol. 13, 1888, p. 103. 51136— Bull. 355—08 2 18 MAGNESITE DEPOSITS OF CALIFORNIA. magnesite directly from the original minerals, but the ordinary ten- dency shown by magnesite bodies is to occur in only those portions of the serpentine which show great decay, the magnesite being probably formed mostly from the serpentine. Van Hise a supposes that in the decay of olivine a third of the mag- nesium may pass into magnesite, in which case he would write the reaction for olivine containing magnesium and iron in the atomic ratio of 3:1 as follows: 3Mg 3 F eSi 2 0 8 + 3C0 2 4“ 4H 2 04" O = 2 H 4 Mg 3 Si 2 0 9 4 “ F 63044 " 3MgC0 3 -l“ 2Si0 2 4" k. Olivine Carbon Water Oxy- Serpentine Magne- Magnesite Quartz Heat dioxide gen tite Here.“k” signifies that heat is liberated. This equation is largely theoretical, and as a matter of fact little magnetite is found in many of the specimens examined. Hydrated oxides of iron are common, however, and it seems probable that to such an equation water should be added to the unknown amount necessary to hydrate the iron. At the same time it is to be remem- bered that vastly more carbonated water is ordinarily present than is required to supply the amount demanded by the equation, so that it seems possible that under certain conditions, with this excess of carbon dioxide at hand, the entire amount of magnesium contained in olivine carrying equal numbers of magnesium and iron atoms may pass into magnesite. Such a change may be represented by this equation: 4Mg 2 Fe 2 Si 2 0 8 +6H 2 0+8C0 2 +40=2(2Fe 2 0 3 .3H 2 0)4-8MgC0 3 4-BSi0 2 . Olivine Water Carbon Oxy- Limonite Magnesite Quartz dioxide gen Enstatite also alters to magnesite, and in a few specimens is wholly replaced by it. Probably other pyroxenes also form magnesite on weathering. It seems probable that as a rule both serpentine and magnesite are formed in the process of decay of the original minerals in peridotites and allied basic rocks, and that during the decay of the serpentine the formation of magnesite is continued. In any case the magnesia or magnesian mineral is changed to the carbonate, dissolved by perco- lating water charged with carbon dioxide, and precipitated in cracks and crevices as veins. The silica is carried away in solution by the water and is often deposited in other veins or with the magnesite veins as opal or quartz. Many magnesite veins stand out prominently from the surrounding serpentine, as they weather less readily than the serpentine, and also because in the vicinity of a magnesite vein the surrounding serpentine is generally much decomposed and therefore erodes rather easily. The boldness of outcrop and the snowy whiteness of the veins form a a Van Hise, C. R., A treatise on metamorphism: Mon. U. S. Geol. Survey, vol. 47, 1904, p. 309. U. S. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. Ill WEATHERED SURFACES OF MAGNESITE. A, From Red Mountain, Santa Clara County; R, C, From locality 4 miles northeast of Porterville. All natural size. GENERAL DESCRIPTION. 19 strong contrast with the dull-colorecl surroundings, so that their occurrence at once attracts the eye. Surfaces of comparatively pure, even-grained magnesite, exposed to the weather, are in many places fluted by the rain, similarly to lime- stone under like conditions, but the flutings or channels are much narrower. Other surfaces are covered with sharp-angled irregular projections, due probably to impurities. (See PI. III.) At Red Mountain, Santa Clara County, earth-covered pieces attacked by per- colating water have weathered into designs resembling mud cracks, with the spaces between the cracks convex and a little over half an inch across. (See PI. IV, B.) In many of the larger veins there is a central portion of compara- tively pure magnesite, and in the same veins on one or both sides there may be many inclusions of serpentine. This mixed condition of the magnesite and serpentine is common in the large veins seen along the Coast Range. Small inclusions of serpentine in many places extend well into the vein. Toward the side the inclusions form a gradually larger proportion of the mass until the magnesite appears only as a great number of small veins in the broken serpentine. Or, if the main mass is approached from the side, as along a tunnel, a stockwork of small veins first appears, growing thicker toward the large vein, until the larger part of the mass is magnesite and the pieces of the ser- pentine are so separated as to become inclusions in the magnesite. This may result from two forms of growth. If any particular group of anastomosing veins grows greatly, the fragments between the veins become so separated that they lose their predominance as compared with the magnesite, and the magnesite forms the greater part of the mass. In the other form of growth the serpentine fragments may be partly or wholly replaced by magnesite. Still other large veins and masses are clear magnesite from the center to one or both sides, either of which may be formed by much slickensided faults. There is considerable difference in the purity of the veins at different places. Some are beautifully white and contain but a small percent- age of foreign matter; others contain iron oxides, silica, clay, or serpentine in varying amounts and proportions. Near the veins the serpentine has almost without exception lost its normal color and is badly rotted and porous as the result of its decom- position by percolating surface waters. The rock shrinks through the gradual removal of its components and the magnesite fills the enlarging spaces between the fragments. The magnesite produced through the decomposition of serpentine occupies about four-fifths of the space of the original rock, so that a magnesite vein may be and probably is formed very largely from the serpentine which formerly occupied the space now filled by the vein, the remainder coming from the rock in a comparatively narrow zone on each side. The large width of some of the veins may thus be explained, by supposing that they occupy the 20 MAGNESITE DEPOSITS OF CALIFORNIA. spaces made by the disintegration of the serpentine almost as fast as they are left, rather than natural fissures or cracks in the rocks. The veins are thus, in a sense, partly residual from the serpentine. In specimens collected fragments of serpentine are to be seen in various stages of decomposition and replacement; in others the fragments are as sharp angled as if freshly broken. Belts of disintegration naturally occur along the channels with greatest circulation of water, generally coincident with the larger faults. Every crack and joint along the line makes a feeder for the trunk channels. Among these reticula- tions the same process of decomposition is going on, and in places abrupt enlargements of the veins occur, making so-called “ bowlders” of magnesite, which may be 2 or 3 feet or even more in diameter and nearly equi dimensional. The formation of such a deposit, on a small scale, is shown in PL IV, A. This lack of linear extension in the small deposits, together with the number of faults known to cut the Coast Range serpentines in every direction, makes the following of veins by widely separated outcrops very uncertain, as the outcrops may be, and many of them are, distinct deposits, though they happen to have a certain alignment. Abrupt terminations are known to - occur in the large deposits as in the smaller ones, and it is unsafe to expect the same continuity as would be thought probable in a quartz vein of equal width. Two modes of precipitation of magnesite from solution suggest themselves. Brucite (Mg(H 2 0) 2 ), formed through the decomposition of magnesian minerals without carbonation, may take the C0 2 from carbonated water carrying magnesite and thus precipitate both the newly formed molecule and the magnesite carried in solution, owing to the loss of excess C0 2 in the water; or magnesite may be precipi- tated from carbonated water owing to the loss of C0 2 through evapo- ration. Nothing resembling brucite has been seen, either in micro- scopic sections or in hand specimens, so that the latter hypothesis seems more likely, though possibly it applies only to the veins depos- ited in more open places, the former process going on in the small threadlike veins. Little is known of the depth to which the veins extend. If they are formed through the agency of percolating surface water, which seems most likely, the manner of precipitation probably has little to do with the depth to which they extend It seems fair to assume that the deposits may be found down to the limit of easy circulation of these waters, a depth of several hundred feet in favorable localities, their size being modified by the time through which such circulation has existed, by differences in the hardness or composition of the rock, etc. Faulting is as likely to cut the veins off in depth as in length. Cinnabar and chromite occur in the serpentines in the neighborhood of many of the magnesite deposits. U. 3. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. IV A. SMALL IRREGULAR VEIN OF MAGNESITE IN SERPENTINE. From Red Mountain, Santa Clara County. B. MAGNESITE WEATHERED UNDER SEVERAL INCHES OF CLAY. The surface is soft. From Red Mountain, Santa Clara County. U. S. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. V A. OUTCROP OF MAGNESITE ON HIXON RANCH, MENDOCINO COUNTY. B. ENTRANCE TO LOWER TUNNEL ON SONOMA MAGNESITE COMPANY’S CLAIM, NEAR CAZADERO. C. OUTCROP OF MAGNESITE VEIN ON WALTERS CLAIM, POPE VALLEY. The face exposed is about 6 feet high. MENDOCINO COUNTY. 21 THE COAST RANGE OCCURRENCES. The individual California deposits will be treated by counties, beginning with the northernmost in the Coast Range and going southward to southern California, then northward along the Sierra Nevada. MENDOCINO COUNTY. Hixon ranch deposits . — On the Hixon ranch, on the east side of Russian River, 12 miles north of Cloverdale, there are a number of outcrops of magnesite, about 600 feet (barometric measurement) above the river, near the crest of a long ridge whose east side slopes steeply to a deep canyon and whose west side falls away more gently toward Russian River. The ridge at this place is formed entirely of serpentine, and it has broken off in successive blocks which are faulted downward toward the river, about. 1J miles away. Behind the fault blocks are hollows in which ponds form. The wagon road following the river crosses the serpentine, which is here reduced to mud and is excessively wet much of the time, owing probably to water that follows the faults and oozes out at this place. The principal outcrop of magnesite (see PL V, A) is almost at the top of the ridge. It is apparently 15 to 20 feet thick and 30 feet long, standing between 4 and 5 feet above the surface, with a westerly dip. On the west side of the vein slickensides in two directions are plainly marked. Two smaller outcrops within 100 yards S. 35° E. (magnetic) from this one may be a continuation of the same vein. Several other veins from a few inches to 1 foot thick outcrop within a few feet of the main exposure, and 200 feet farther west are a number of smaller, less pure, and less continuous veins. It seems probable that the veins are not continuous to great depth owing to the recency of the faulting, by which they would have been cut off. No work has been done on any of the veins. The magnesite in the main outcrop is white and remarkably pure, especially as regards its freedom from lime. A partial analysis by A. J. Peters, at the St. Louis laboratory of the United States Geo- logical Survey, gave the following result: Partial analysis of magnesite from J. M. Hixon ranch. [Solution of air-dried material.] Silica (Si0 2 ) ! 0.41 Alumina (A1 2 0 3 ) 28 Ferric oxide (Fe 2 0 3 ) 12 Lime (CaO) 03 Magnesia (MgO) 47. 16 Carbon dioxide (C0 2 ) 51. 88 99.88 22 MAGNESITE DEPOSITS OF CALIFORNIA. As occasionally noted at other places, the magnesite shows shrink- age cracks (see PL VI, A) as if it had shrunk after deposition. This suggests the probability that it may have been deposited in the form of a hydrous carbonate. Smaller deposits are said to occur near by, but they were not seen by the writer. SONOMA COUNTY. Creon deposit . — Four miles north of Cloverdale a number of mag- nesite veins outcrop in extremely irregular serpentine dikes, on a spur running southwestward from the mountains on the east side of the Sonoma Valley. The deposits are about 1,000 feet (barometric measurement) above Cloverdale, on a steep road, but the haul is all down hill. The dikes in which the serpentine occurs are in places but a few feet wide, cutting an arkose similar to that in San Mateo and other Coast Range counties, where the rock is Cretaceous in age. They also cut some finer sediments. Other dikes are of diabasic charac- ter, and there is considerable glaucophane schist debris, though none was seen in place. The relations of the serpentine to the country rock are obscure, but it seems probable that the dikes are so faulted as to be locally discontinuous. At the time this deposit was visited (November 29, 1906) work was being prosecuted by the Magnesite Products Company, of West Berkeley, Cal. Magnesite veins, from 6 inches to a foot wide, outcrop on the sur- face at a number of pieces, but they show little continuity. At the main outcrop, which was close beside the road, a short tunnel cut a pocket of magnesite which was about 10 feet wide, 15 to 16 feet high, and 40 to 50 feet long. The serpentine is so faulted that if the mass ever continued onward it is now impossible to predict where the remainder may be found. About 500 tons was taken out and the workings abandoned. One-fourth mile N. 10° E. a vein 8 to 12 inches thick is exposed alongside the road, and half a mile east of the main workings a face of magnesite 9 feet high is exposed below the road. A tunnel 15 feet long had been driven into it, at the end of which the magnesite thinned and contained serpentine. Besides these veins there were a number of smaller outcrops at other points in the neighborhood. The magnesite in the worked deposit is but little discolored and portions are pure white, but all through it is scattered some ser- pentine only partially altered to magnesite. The mass has been much crushed and the pieces have been recemented by crystalline magnesite of a slightly greenish yellow color, which forms a layer U. S. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. VI CRACKS IN MAGNESITE APPARENTLY DUE TO SHRINKAGE. A, Compact magnesite from Hixon ranch, Mendocino County; B, Less compact magnesite coated with a thin layer of quartz, also cracked, from locality 4 miles northeast of Porterville. SONOMA COUNTY. 28 about one thirty-second of an inch thick around the fragments. In places colorless fragile platy crystals coat the cavities. A partial analysis by A. J. Peters of a sample as nearly representative as could be selected gave the following results: Partial analysis of magnesite from Creon deposit. [Solution of air-dried material.] Silica (Si0 2 ) - - - Alumina (A1 2 0 3 ) Ferric oxide (Fe 2 0 3 ) Lime (CaO) Magnesia (MgO) Carbon dioxide (C0 2 ) 1.60 .25 1.09 1.04 45.20 50.43 99.61 No analysis was made of the magnesite from the other veins, which is less pure, part being yellow in color. Eckert ranch deposits . — Three deposits of magnesite are said to occur on the Eckert ranch, on the edge of the valley 2 miles east of Cloverdale, but only two were seen by the writer. The more north- erly is not more than 200 yards from the public road. Here on a soil-covered hillside a considerable amount of magnesite, roughly estimated at between 100 and 200 tons, has been excavated and piled up. The hole from which it was taken has been so filled with dirt that nothing could be seen of the rocks nor of magnesite left in place. The mineral is considerably stained, brownish and yellow, and gives the impression of being much more impure than it really is. Here too the magnesite is considerably cracked and the apertures are coated with a transparent crystalline magnesite, which at first glance looks like quartz. A partial analysis by A. J. Peters is as follows: Partial analysis of magnesite from north outcrop on the Eckert ranch. [Solution of air-dried material.] Silica (Si0 2 ) 0.51 Alumina (A1 2 0 3 ) 1.98 Ferric oxide (Fe 2 0 3 ) 16 Lime (CaO) 59 Magnesia (MgO) 45.84 Carbon dioxide (C0 2 ) 50. 80 99.88 In a plowed field, a quarter of a mile southeast of the occurrence just described, several rounded outcrops of magnesite, up to 4 or 5 feet across, occur in a line through a distance of about 75 feet. There has not been enough excavation to show whether they belong to one vein or whether they are merely nodules of large size. No relation- ship between these outcrops and the northern deposit can be traced. 24 MAGNESITE DEPOSITS OF CALIFORNIA. The magnesite is much whiter and purer than that in the northern deposit, and is nearly free from lime. A partial analysis by A. J. Peters is as follows : Partial analysis of magnesite from southern outcrop on Eckert ranch. Silica (Si0 2 ) -• 0. 23 Alumina (A1 2 0 3 ) 04 Ferric oxide (Fe 2 0 3 ) 20 Lime (CaO) 19 Magnesia (MgO) 46.88 Carbon dioxide (C0 2 ) 51.57 99.11 - George Hall ranch deposit . — About 3 miles southeast of Clover- dale, on the George Hall ranch, in the south ba^ik of a deep ravine running toward Russian River, there is a small outcrop of magnesite about 20 feet above the bed of the stream. Although the magnesite is white and appears to be of good quality the outcrop is only 4 or 5 feet broad in greatest dimension, so that it gives little promise of value. Pat Cummings claim . — The Pat Cummings deposits are in a ser- pentine hill or 3 miles S. 35° W. (magnetic) from Cloverdale, at a height of about 1,200 feet (barometric) above that town. At the northernmost occurrence a few tons of magnesite has been mined and thrown out, but none can be seen in place. The magnesite is white, but like that in most of the other deposits has been much brecciated. The cracks between the fragments, however, instead of being coated with crystalline magnesite as is usually the case, are lined with clear colorless chalcedony, so that the percentage of silica present is large. About one-fourth of a mile farther south are two outcrops of impure magnesite 8 to 12 feet in diameter. Gilliam Creek deposits . — In the northwest corner of sec. 6, T. 8 N., R. 10 W., Mount Diablo base and meridian, on the steep western side of Gilliam Creek, 400 or 500 feet above the stream and about 7 miles northwest of Guerneville, are a number of large outcropping veins of magnesite. They occur in a space about 300 feet long, following the creek, and about 100 feet wide, measured along the slope. The country rock is as usual a serpentinized basic rock. The veins stand out boldly; one near the southern side of the claim is 6 to 8 feet thick and rises more than 20 feet above the hillside. Great masses of mag- nesite have fallen from the outcrop and lie on the surface or are partly buried in the debris. There are many smaller veins and probably one or two as thick as that from which the outcropping portions have broken, so that, as float or outcrop, several thousand tons of magnesite in large pieces are in sight. Other veins undoubt- SONOMA COUNTY. 25 edly occur north of this deposit, as there are many bowlders of magne- site in the creek. Smaller deposits are said to occur down the creek (south) from the main outcrops. Except the deposits at Red Moun- tain, these are from surface indications the most extensive seen by the writer in California. The magnesite here, however, contains a greater amount of impurities than that at Red Mountain. (Compare analyses on p. 36.) A partial analysis, made by A. J. Peters, of a sample picked to be as nearly representative as possible, was as follows: Analysis of magnesite from west side of Gilliam Creek. Silica (Si0 2 ) 3.51 Alumina (A1 2 0 3 ) 1.10 Ferric oxide (Fe 2 0 3 ) 80 Lime (CaO) 1.46 Magnesia (MgO) 43.65 Carbon dioxide (C0 2 ) 49.16 99.68 This magnesite is probably too impure for use as a material for cement, but should make brick which would compare well with the Austrian, and is good for gas and wood-pulp bleaching. The property is owned by the Western Carbonic Acid Gas Company. About a mile of new road was necessary to connect the deposit with an established highway, and this was being constructed at the time of the writer’s visit (December 3, 1906). No magnesite had then been shipped from the deposit. Madeira deposit . a — The Madeira deposit was unknown to the writer at the time of his trip into Sonoma County, and so was not visited. It is in sec. 31, T. 9 N., R. 10 W., which adjoins on the north the sec- tion in which is located the Western Carbonic Acid Gas Company’s claim, and is said to be a rather extensive deposit of magnesite con- taining considerable silica. The best exposures are said to be along a small tributary of Gilliam Creek. It will be necessary to build between 1 and 2 miles of wagon road before the magnesite can be hauled to the railroad. Unnamed deposits . — About three-fourths of a mile northwest of the Western Carbonic Acid Gas Company’s deposit, probably in sec. 36, T. 9 N., R. 11 W., near the top of a high hill, are a number of magne- site veins from 2 to 10 inches or more in thickness. One vein about 10 inches thick is exposed broadside along the face of a bluff perhaps 30 feet high. The quality of the magnesite here is apparently very good, though a number of the veins contain much serpentine. At one place there is a reticulated vein whose individual members are from 4 to 8 inches thick. This vein, which was formerly made up of a Data furnished by Chester Naramore. 26 MAGNESITE DEPOSITS OF CALIFORNIA. opaque white magnesite containing some serpentine, has been much broken. Around the fragments light-green, radially crystallized mag- nesite has formed, and cavities that still remained have been filled with milky chalcedony. The mass now consists largely of the green crystalline magnesite and is striking in appearance. It is said that at one time an attempt was made to work the deposit for ornamental stone, under the impression that it was Mexican onyx (onyx marble). There are too many imperfections in the material to make it desirable for this use. An old road, now fallen into bad repair, leads past the deposit to another road running to Healdsburg, which is about 11 miles distant. Should it become desirable to work these veins, the railroad could probably be reached more easily at Healdsburg than at Guerneville. Magnesite float was seen in a number of creeks in the neighborhood, showing the existence of other deposits, whose extent is unknown. Red Slide deposits . — The Red Slide deposits are situated near a natural feature known by that name in the valley of East Austin Creek, in T. 9 N., R. 11 W., about 84 miles by road north of Cazadero. The serpentine on the high hill in which the deposits are situated is stained with iron oxide, and there is so much slipping of the rock that vegetation can not exist on that portion of the hill, whence the name “Red Slide.” It may be seen from other hilltops for long dis- tances and so is a familiar landmark. A large belt of serpentine, whose limits are unknown, runs through this portion of the country, and in it occur the magnesite deposits. In the group examined, which lies on the west side o N f the creek, there are several outcrops up to 5 and 6 feet wide and a number of smaller ' ones. At the time the deposits were visited (December 4, 1906) the Sonoma Magnesite Company was doing development work on them. Two tunnels had been run into the hill, one a few feet above the creek and the other about 80 feet higher up the hill and 100 feet or so upstream. The upper tunnel was well driven, 93 feet long, 6 feet high, and 7 feet wide. Three veins 5 to 6 feet thick and a number of smaller ones had been cut. There was but little work to show the extent of the veins beyond their thickness and they could not be followed on the surface. Much more development work is said to have been done since then. At one point magnesite was said by Mr. E. W. Arnold, the superintendent, to have formed during the preceding winter, and it gave much evidence of being a recent deposit. Water trickled over a face of magnesite exposed by mining, and a soft nodular deposit, somewhat resembling a spring deposit of calcite, covered that portion of the wall. Owing to the fact that shrinkage cracks are frequently found in magnesite, the question arose in the writer’s mind as to whether magnesite was not deposited as a hydrous car- SONOMA COUNTY. 27 bonate, and a specimen of the material was collected and later tested in the Geological Survey chemical laboratory, where it was pro- nounced anhydrous. Evidence of considerable faulting appears in the upper tunnel and small veins show dislocations of a foot or less. One of the larger veins was followed for but a few feet before it gave out. The lower level was 200 feet long and of the same cross section as the upper one. It started in on a vein of magnesite which appeared to be about 9 feet wide (PI. V, B), but the entrance is not at right angles to the vein, and the magnesite on the right side of the vein grades into serpentine. There is probably not more than 6 feet of clear magnesite. The tunnel did not follow this vein far and only one other was cut. This second vein has been faulted, and though apparently about 6 feet wide, but little could be told of its extent. The attempt to crosscut the veins cut in the upper tunnel was unsuc- cessful. It seems altogether likely that the general remarks about the indefinite extension of magnesite veins in any direction will apply with full force here. These veins will probably be found to be of much less length and depth than might be expected from their width, if they were to be judged by the ordinary characteristics of quartz veins. The magnesite is of a creamy color and contains considerable silica. It is, however, remarkably free from lime. A partial analysis, by A. J. Peters, of a sample selected to represent as nearly as possible the average rock gave the result stated below. There is no doubt that better or worse specimens might be taken. Analysis of magnesite from Red Slide deposits. Silica (Si0 2 ) 7.67 Alumina ( A1 2 0 3 ) 26 Ferric oxide (Fe 2 0 3 ) 29 Lime (CaO) 04 Magnesia (MgO) 43.42 Carbon dioxide (C0 2 ) 48.08 99.76 A large quantity of magnesite, estimated by Mr. Arnold to be almost 2,000 tons, though this figure seemed somewhat large to the writer, lies on the dumps. There is also a good deal of float magne- site in the creek. The road from the workings to Cazadero crosses a mountain with grades so steep that it is impossible to haul the mag- nesite out at a profit. The road to Guerneville is as bad, or worse, and longer, so that at present the magnesite can not be marketed. Should a way to haul the rock out be obtained, the company expects to make artificial stone and tiles. The company claims to have a much better deposit 2\ miles farther up the creek, where a vein is said to be from 10 to 25 feet thick and to have been followed for 900 feet. 28 MAGNESITE DEPOSITS OF CALIFORNIA. Norton ranch deposits . a — On the Ed. Norton ranch, along Dry Creek, 10 miles northwest of Healdsburg, is a deposit of rather siliceous magnesite in large rounded chunks lying upon serpentine and over- lain by clay and black soil. There is no outcrop, and the magnesite is exposed only by trenches. NAPA COUNTY. General remarks . — Like all the other counties along the Coast Range, Napa County has a rough topography, so that railroad and wagon-road building over most of it is difficult. The beautiful Napa Valley, from 1 to 4 miles wide, runs the whole length of the western side of the county, and east of it, separated by rough hills, lie Chiles and Pope valleys, of much less extent. Only in the Napa Valley is there a railroad, though projects for an electric road to traverse both of the other valleys on its way to Lake County have been agitated for many years. At one time grading was done over a part of the route, and later another company constructed a road for a portion of the distance through the Napa Valley. All the known deposits in this county are situated east of the Napa Valley, with rather long and, in some cases, difficult hauls to the railroad. Rutherford is the most easily reached station and the road through Conn Canyon is the first stretch of the route to any of the deposits. Walters or White Rock deposit . — The deposit bearing this name is located in the NE. \ sec. 11, T. 9 N., R. 5 W., on the east side of Pope Valley, 22 miles northeast of Rutherford. The distance from the railroad makes hauling expensive, and the claim, which was never worked on a large scale, has made no production for several years. The proposed electric road from San Francisco to Lake County, if built, will pass within 4 miles or less of the deposit, and the claim will then be in an excellent position to ship magnesite. The deposit is situated about three-fourths of a mile from a public road in a hill of serpentinized lherzolite, about 400 feet (barometric measurement) above the valley. It is composed of a large number of veins whose exposures range in width from a fraction of an inch to 12 feet and lies on both sides of a small ravine that forms an amphitheater, with an easy, straight southward grade to the valley, making an almost ideal place to work with an aerial tram. The veins are in three principal groups, two of which lie on the east side of the ravine and the other on the west. The main group on the east side comprises three large veins of magnesite that can be definitely traced for distances of about 140, 250, and 230 feet, with strikes of N. 28°, 30°, and 45° W., respectively. At their north ends the western and eastern veins are but 30 feet apart, and the middle a Description furnished by Chester Naramore. NAPA COUNTY. 29 vein probably converges with the eastern one. A shallow shaft on the western vein shows its dip to be 50° N. 62° E. The veins stand out boldly and can be seen from any part of the valley not hidden by hills. (See PL V, C.) Longitudinal faults occur in both of the outer veins. Between the large veins are many smaller ones having a general parallelism to the main bodies. At its widest ex- posure the western vein is about 10 feet thick, of which about 5 feet on the foot wall is solid white magnesite, although the upper 5 feet on the' hanging-wall side contains many inclusions of serpentine. The structure of the eastern vein is similar, and in places the magne- site may be seen grading into the country rock; it is about 12 feet wide where exposed in a shallow crosscut. In the middle vein a width of 18 inches to 5 feet of clear white magnesite is exposed. There has been some crushing of the magnesite and the broken par- ticles have been cemented with yellowish, less pure material. Part of the magnesite has formed in yellowish botryoidal masses that are rather impure. Some crystalline magnesite, similar to that of Chiles Valley, is found in the crevices. It is said that 1,250 tons was mined between 1894 and 1899, being simply broken from the exposed faces of the veins. A second group with a more northerfy strike lies 100 feet or more above the veins just described. The veins forming this group are smaller, running from 2 inches to 2 feet in width, and the larger of these are impure. There are also many scattered veins in the inter- vening space. On the west side of the ravine, 200 to 250 feet from the veins first described, is a third group with a strike between north and north- west. The largest vein is 4 to 6 feet wide; and seven others from 1 to 2 feet wide occur within 125 feet. All appear to be of excellent quality. It would seem possible to blast out the whole of the rock through this distance and hand-pick it at a profit should the deposits again be worked. ' A prospect tunnel was run into the hill near these veins and struck an irregular vein of crushed magnesite at the end. Snowflake and Blanco claims . — Magnesite was mined by Bartlett & Stanley at a place about 2 miles south of the old Chiles mill, in Chiles Valley, and 10 miles from Rutherford, for a number of years, but the mine has not been operated since 1900, as it is too far from the railroad to compete with points having better shipping facilities. Here also the country rock is the serpentine of the Coast Range, inclined to a dark-green or blue-black color. The deposits are on the west side of the valley, in a small serpentine hill skirted by a pub- lic road, and consist of a number of veins which range in thickness from 1 foot to 6 feet and are said to have been as much as 12 feet wide. Where seen, however, the larger veins were considerably mixed with serpentine and other impurities. Marked faulting occurs with the 30 MAGNESITE DEPOSITS OF CALIFORNIA. veins, and both the hanging and foot walls are generally fault planes. The serpentine is much broken and greatly decomposed in the neigh- borhood of the veins, the interstices being filled by smaller veins of magnesite. On the foot walls of several of the veins extensive silicification has taken place, the serpentine being hardened through 2 or 3 feet. The veins are locally brecciated and cemented with less pure material of yellowish color, the original magnesite being a clear white. At many places in the brecciated portions each fragment is covered by magnesite in radial crystals, forming a coating up to half an inch thick and varying in color from crystalline clearness to delicate green and yellowish green. Cracks in the serpentine are also filled with the same crystalline magnesite. This material is strikingly different from the ordinary magnesite, which shows no crystal form to the unaided eye. In places crevices in the veins have a velvety black coating of pyrolusite (manganese dioxide), making the rock look as if it were coated with lampblack. A small amount of chromite has been found in the neighborhood, but not in paying quantities. Partial analyses of magnesite from this mine are given below : Partial analyses of magnesite from the Bartlett 6c Stanley mine , Chiles Valley. 1. 2. 3. Silica (Si02) - - - 2. 15 1.22 1. 16 5.28 41.01 48.72 1.81 } .08 Trace. 46.55 51.25 .32 6.68 15. 10 Alumina (AI2O3) Ferric oxide (Fe 203 ) Lime (CaO) Magnesia (MgO) 37.23 40.98 Carbon dioxide (CO 2 ) Water and undetermined 99. 54 100.00 99. 99 Analysts: No. 1, P. H. Bates, United States Geological Survey; Nos. 2 and 3, Abbott A. Hanks, San Francisco, October 1, 1903. Specimen No. 1 was collected by the writer and was as near]y representative as was possible to select; No. 2 was probably a picked sample, and No. 3 was of a poor quality, not shipped. The lime content of the first specimen is very high. During the time that the mine was worked probably 10,000 to 12,000 tons of magnesite was taken out and calcined. As pure magnesite loses more than half its weight by being calcined, a large saving was made in haulage by getting rid of the carbon dioxide when the material was to be used as magnesia. A four-sided shaft furnace, built of serpentine and sandstone blocks and lined with fire- brick, was used. It was about 15 feet high and from 3 to 5 feet across. The furnace was fired from the four sides at the base of the shaft, largely with manzanita, a hard-wooded shrub making a hot SANTA CLARA COUNTY. 31 fire, and the calcined magnesite was withdrawn from below. The waste magnesite fines below the furnace have compacted noticeably from recarbonation. Priest deposit. 0 ' — D. C. Priest has a magnesite deposit in Chiles Valley, in sec. 23, T. 8 N., R. 4 W., about 13 miles from Rutherford. One 2-foot and one 18-inch vein are exposed, well up a hillside, and magnesite of a rather poor quality is exposed in a lower opening. No work has been done on the deposit for a number of years. Russell deposit. 0 -— E. T. Russell holds a claim in sec. 24, T. 8 N., R. 4 W., on which several small magnesite veins outcrop. About 25 tons was shipped at one time. The deposit is 4 miles from a road and 15 miles from Rutherford. Matthai deposits . 0 — Frank Matthai formerly held a claim known as the “North mine” in Soda Creek canyon, in the NE. \ sec. 35, T. 8 N., R. 4 W., near the public road. Irregular veins and masses of magnesite several feet thick outcrop in serpentine on this claim. Bartlett & Stanley mined the larger masses by open cuts in 1895, but the property has been idle since. Much magnesite still remains in sight. The “South mine,” also held by Mr. Matthai, lies a quarter of a mile southeast of the “North mine,” on the other side of a low ridge, on the north bank of Greasy Camp Creek. A 5-foot vein of clear white magnesite outcrops along the creek for about 30 feet, dipping into the hill at a low angle. At the time the mine was visited (1905) two open cuts and a short tunnel had been made, and about 100 tons of magnesite was piled up. SANTA CLARA COUNTY. Deposit near Coyote . — A small deposit of magnesite occurs on W. W. Burnett’s ranch, about 3 miles northeast of the Coyote railroad station and half a mile north of the summit of the Metcalf road. The deposit occurs near the top of the east slope of a hill several hundred feet high in a belt of impure serpentine, which weathers in rough, irregular forms. The exposed portion of the vein is about 100 feet in length and 4 to 10 feet wide, striking N. 35° W. (mag- netic), apparently with a nearly vertical dip. A ravine cuts off the vein on the south, but some pebbles of magnesite were found on the south side, so that there may be on that side either another deposit or an extension of this one. The main part of the vein is of good quality, but a part of the magnesite is rather siliceous and con- tains fragments of serpentine now almost entirely replaced by silica and magnesite. The fragments on the surface south of the ravine are still more impure. a Data furnished by Chester Naramore. 32 MAGNESITE DEPOSITS OF CALIFORNIA. A partial analysis by A. J. Peters of a specimen from the large vein gave the following result: Partial analysis of magnesite from W. W. BurnetVs ranch , Coyote. Silica (Si0 2 ) 0. 30 Alumina (A1 2 0 3 ) . . .16 Ferric oxide (Fe 2 0 3 ) 38 Lime (CaO) 1. 34 Magnesia (MgO) 45.86 'Carbon dioxide (C0 2 ) 51. 80 99.74 The magnesite seems to be suitable for brick, g%s making, and paper making, but probably has too much lime to make good oxy- chloride cement. As is usually the case, the serpentine is much more decayed near the vein than in other places. On the west wall of the vein the ser- pentine is so much impregnated with magnesite that it has a gray appearance for a thickness of several feet. In other places it has a glassy aspect over small areas, but the quantity is too small and the serpentine is too much cracked to permit its utilization as an orna- mental stone. Many small veins of cryptocrystalline quartz cut the serpentine in various directions. In some of the veins are small vugs showing crystallized quartz. Bay Cities Water Company’s land . — A couple of miles northeast of Morgan Hill station Coyote Creek turns abruptly to the west from a northward course and flows through a serpentine ridge into the Santa Clara Valley by way of a narrow cut, on the north side of which are several veins of magnesite. The serpentine in which they occur is similar to that east of Coyote station, and may be a part of the same dike. The lowest vein is perhaps 250 yards west of San Felipe Creek, which joins Coyote Creek at its westward bend. The outcrop of the vein strikes N. 85° E., is about 10 feet wide and 50 feet long, and forms the point of a small hill. The magnesite is made up of rounded irregular particles ranging from half an inch downward in diameter (see PL VII, B) y cemented by siliceous magnesite, which for an inch or more from the surface is stained red by iron. Many chunks of iron-stained quartz 2 feet or more in diameter lie on the ground near the outcrop. No work has been done on this vein. About 100 feet farther up the hill is a larger deposit of rather impure magnesite, which does not carry so much silica, but has much serpentine mixed through it. A number of extremely irregular veins interlace through an area 200 feet long by 50 to 100 feet wide. In places the magnesite has an oolitic structure, analogous to the struc- ture of the vein lower down the hill, but the particles are all small, U. S. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. Vll STRUCTURE OF MAGNESITE ON BAY CITIES WATER COMPANY'S LAND ON COYOTE CREEK. ^1, Specimen from Ihe upper deposit, showing a natural surface; B, Specimen from the lower deposit, showing a smoothly ground surface. Both natural size. SANTA CLARA COUNTY. 33 only a few grains reaching one-eighth inch in longer diameter. (See PI. VII, A.) At the outer part the fragments are separated by talcose matter, but the mass becomes gradually more compact until the particles coalesce and form dense, solid magnesite. The prin- cipal vein runs almost parallel with the course of the hill, and a face 10 to 20 feet high has been exposed by a cut. In places segregations of clear-white magnesite reach 2 to 3 feet in thickness, but other portions of the vein are but a few inches thick. The material could be hand picked and a fair to good quality obtained. An old sheet-iron furnace is in ruins on the ground, and it is said that an attempt was made to calcine the magnesite some years ago. Several carloads of the raw material are reported to have been shipped. Mrs. A. F. Cochrane’s land . — About 1J miles south of the junction of Coyote and San Felipe creeks and about 3J miles from Morgan Hill station, on the land of Mrs. A. F. Cochrane, is a rather bold outcrop, several feet wide, of a fine-grained buff-colored magnesite, which can be followed for more than 200 feet up the hill. The serpentine shows much silicification and iron staining. In places blocks 8 or 10 feet thick are almost tvholly replaced by iron- stained quartz. Elsewhere the cracks in the serpentine have been filled with quartz, very much as at other deposits the cracks have been filled with magnesite. The serpentine between the quartz veins is much decayed and in places drops out, leaving an irregular skeleton of silica much stained with yellow and red iron oxides. The great amount of iron present in this locality is very noticeable, and to it the magnesite probably owes its buff color, although the analysis shows but 0.18 per cent of ferric oxide. Silica makes nearly half of the rock. A partial analysis by A. J. Peters is as follows: Partial analysis of magnesite from Mrs. A. F. Cochrane's land, near Morgan Hill. [Solution of air-dried material.] Silica (Si0 2 ) Alumina (A1 2 0 3 ) Ferric oxide (Fe 2 0 3 ) Lime (CaO) Magnesia (MgO)... Carbon dioxide (C0 2 ) 99.45 49.85 3.45 .18 .48 21.53 23.96 In places small fragments of dull-yellow magnesite are included in the quartz. It is reported that some work was done on the deposit in 1897 and that several carloads of magnesite were shipped to San Francisco. Red Mountain deposits . — Near Livermore, a town 48 miles south- east of San Francisco, there are a number of magnesite deposits, of which the only one now being worked is that of the American Mag- 51136— Bull. 355—08 3 84 MAGNESITE DEPOSITS OF CALIFORNIA. nesite Company, 32 miles southeast of Livermore on Red Mountain, in the northeast corner of Santa Clara County, along the Stanislaus County line. A number of the company’s claims are located in the latter county. From Livermore an excellent road follows up the Arroyo Mocho, crossing into and running down the Arroyo Colorado. The maximum grade for the haul from the mine is said to be 3 per cent. At the mines the company has erected good buildings and roads, and an aerial tram 2,500 feet long, with a capacity of 100 tons per ten-hour day, delivers the magnesite to bunkers, from which it is loaded into wagons for hauling to Livermore. An attempt was made to haul the magnesite with oil-burning traction engines draw- ing two iron wagons carrying 17 J tons each, and two such trains were put into operation, but are reported to have been unsuccessful. The haul to the railroad is very long for a product of no greater value than magnesite, and can scarcely be profitable. The magnesite is shipped to Oakland, where the company’s factories for brick, carbon dioxide, and other products are situated. The mine offices and other buildings are located near springs that give sufficient water for the engines, the mine, and other purposes. The country rock is lherzolite and peridotite, in some places much serpentinized and in others remarkably fresh. The magnesite occurs in the more altered portions. Although these deposits have been known for a long time, they were not worked until 1905, owing to their distance from a railroad. They occur in a number of veins in a group around a small valley, so arranged as to be excellently located for working by adits and an aerial tram. Just how many veins there are can not be stated, as the brief time at the writer’s disposal did not allow examination of the smaller ones. Owing to debris and faulting it is not possible to tell whether many of the outcrops belong to the same veins as neigh- boring ones or whether they are separate deposits. In the immediate vicinity there are, however, probably 10 or 12 veins, and possibly more, 2 feet or over in thickness, all of which could be well worked with but slight changes in the plant installed. The veins stand out prominently in the bright sunshine of the val- ley and are almost dazzlingly white, so that they can be seen from the higher hills miles away. One of the veins, called the “Mammoth,” stands fully 10 feet above the hillside. The magnesite shows a number of peculiarities in weathering. Some of the surfaces weather into a pattern that looks like sun cracks in mud (see PI. IV, B), wdth flatly oval surfaces from one- eighth to three-fourths of an inch wide between the cracks. In places there are fluted surfaces, such as occur on exposed limestones, but in narrower lines (see PI. Ill, A), and locally the weathered surface is thickly studded with sharp points. Many exposed sur- faces are covered with a white powder which has been supposed to SANTA CLARA COUNTY. 35 be magnesium oxide or hydromagnesite, but which has been deter- mined to be another form of magnesite. Underground also nodules or portions of veins of magnesite in places have turned to this powder, leaving a core of solid material. Mr. C. H. Spinks, the superintend- ent of the mines, told the writer that certain other veins a few miles distant, belonging to the company, carried very much more of this powder. Powdery magnesite has been described as occurring also in South Africa. (See p. 60.) Why it should take this form, breaking down from the solid state without apparent chemical change, is unknown. Only one vein on the Alameda claim, near the top of the ridge, was being worked in November, 1905, when the claims were visited, and the first magnesite was shipped in that month. This vein has a strike of N. 30° W. (magnetic), with a steep southwesterly dip. It ranges in thickness from 15 to 40 feet, and could be definitely followed for about 300 feet S. 30° E. from faults against which it ends at the north. Whether the vein has been faulted off or whether its ter- mination was originally fixed by the fault was not clear. Although the fault mud and breccia contains some crushed magnesite, this may come from other sources. Veins of rosiny opal and an aluminous siliceous material, 1 inch to 3 feet thick, occur along the fault. The magnesite is also badly cut and crushed by faults and contains in places much serpentine and some of the aluminous siliceous veins. On approaching the vein through the tunnel one sees that the ser- pentine is greatly decayed and is cut in every direction by innumer- able small veins of magnesite, crossing each other at all angles. Here and there, in veins which do not exceed 2 or 3 inches in thickness, sud- den enlargements occur, which may be 3 feet in diameter and almost equidimensional. These are referred to as “bowlders,” but they have nothing in common with bowlders beyond size and shape. Some of the smaller nodules are partly composed, mostly in the outer portion, of aluminous and siliceous material, the inner portion appearing to be comparatively pure magnesite. This material seems to be a replacement of the magnesite similar to the replacement of calcite by silica. The small veins grow in number and in thickness until by steady gradation the mass of comparatively pure magnesite is reached. At other points the vein’s walls are abrupt and are probably delim- ited by faults. The vein was pierced by several adits on different levels, and a crosscut at one place entered the vein for 35 feet without going through it. A drill hole 8 feet long at the end of the crosscut was said not to have reached the other side. The magnesite is pure white, the crosscut looking as if freshly whitewashed. As is to be expected in a serpentine area, faults have cut the vein in a number of places, and through at least a portion of their length both hanging and foot walls are fault planes. 36 MAGNESITE DEPOSITS OF CALIFORNIA. At several places pipes or nearly vertical channels, 6 inches and upward in diameter, now largely filled with clay, have been cut through the magnesite by water. The walls of these* channels are much smoother than those of most similar channels cut in limestone, owing probably to the homogeneous composition of the magnesite. At two places the watercourses were large enough to use as chutes. Mining is carried on by means of an open cut, in which the magnesite is quarried and allowed to fall through an upraise to an adit below, whence, it is moved in cars to the aerial tram. The tramway drops 600 feet in the 2,500 feet to the bunkers. The skips are placed 500 feet apart and each carries 1,000 pounds of magnesite. On the Canada claim, several hundred feet down the hill from the worked vein, is a large irregular outcrop of magnesite, between 40 and 50 feet across, which had not been prospected at the time the claim was visited. Later it was reported that a prospect tunnel run under this outcrop had shown the magnesite to contain much included serpentine. Just across the ridge from the point at which mining was being carried on is the outcrop of the u Mammoth’’ vein, already referred to, which stands more than 10 feet above the hill slope on its lower side. It is about 4 feet thick and apparently is of excellent quality. It had not been prospected, so that nothing could be told of it beyond its outcrop. A number of other veins in the group are up to 10 feet wide and at least one can be followed for 200 yards. They are not all equally pure, and several contain a considerable amount of included ser- pentine. Extravagant estimates of the amount of magnesite in sight have been made, but though the amount exposed is large, the develop- ment at the time the deposits were visited was not extensive, and from the outcrops alone but two dimensions can be known, so that estimates of the total amount available are but little better than guesswork. Ravines cutting across the strike of the veins do not expose them and show that they are continuous for long distances. The following are partial analyses of magnesite from the Alameda claim : Partial analyses of magnesite from Alameda claim , Santa Clara County. 1 . 2. Rilioa. (SiOj'i 0.73 .14 .21 .40 46. 61 51.52 3.93 } .20 1. 16 Alumina, ( AI 2 O 3 ') Ferric oxide (Fe20s) Tiimfi CCa.O'l Magnesia (MgO) - . .. Carbon dioxide (C^j) 09. 61 5.29 ALAMEDA AND STANISLAUS COUNTIES. 37 Analysis No. 1 was made by A. J. Peters, of the United States Geological Survey. No. 2 was made by E. T. Allen, of the Carnegie Institution geophysical laboratory, to determine the amount of im- purities present, preparatory to using the magnesite in his experi- mental work. Both specimens were collected by the writer, and the second was picked out for its whiteness under the supposition that it would be especially pure. F. E. Wright determined microscopically that the silica was present as quartz, and not as combined silica. Close to the magnesite veins, about 250 yards southeast of the present workings, are small impregnation veins of chromite. The chromite occurs in grains from the size of a pea downward, and can be clearly seen to spread from joints in a serpentinized peridotite. It is accompanied by a pale lilac-colored chlorite, probably either kotschubeite or kammererite. A small amount of work has been done on the veins, but the prospects do not seem to have been encour- aging. A little cinnabar is said to have been found in the neighbor- hood, and two mercury mines are being developed within a radius of 4 or 5 miles. On Cedar Mountain, in Alameda County, the company had also located eight magnesite claims which, however, were not being worked and were not visited. Other Santa Clara County deposits . — There were said to be other deposits in the neighborhood of Coyote, but the locations given were so indefinite that they could not be found. Small deposits are said to occur in Alum Bock Park, near San Jose, and in the vicinity of the mercury mines at New Almaden, but they are without commercial importance. From the amount of serpentine in the county it is rather to be expected that there should be other occurrences of magnesite. ALAMEDA COUNTY. 0 King claim. —Two miles from the Arroyo Mocho road and 22 miles southeast of Livermore, on the King claim, several small veins of magnesite are exposed in a cut. There has been no production. Bantams camp deposit. — In sec. 16, . T. 5 S., R. 4 E., on a narrow ridge southwest of Banta’s cabin in the Arroyo Mocho canyon, 24 miles southeast of Livermore, is a small outcrop of magnesite. There has been no development. STANISLAUS COUNTY. vSome of the American Magnesite Company’s deposits (see p. 34) are in Stanislaus County, adjoining the Santa Clara County line. It is probable that other deposits occur along the western edge of the county, where the brushy, sterile hills of the serpentine area are but seldom traversed. a Data furnished by Chester Naramore. 38 MAGNESITE DEPOSITS OF CALIFORNIA. SAN BENITO COUNTY. Extensive areas of serpentine occur in San Benito County, in which are located the New Idria mercury mines, now the largest producers in California. No magnesite has been reported, but it is probable that it may yet be found. At present transportation facilities are poor, and in wet weather the roads are very bad. SAN LUIS OBISPO COUNTY. Magnesite in small veins is reported to occur on the Kiser place, 8 to 9 miles northwest of Cambria. The country is rough and the deposits are a long way from railroad transportation. San Simeon, a port of call for coastwise vessels, is the nearest shipping point. SANTA BARBARA COUNTY. Specimens of magnesite seen at Santa Barbara were said to come from a deposit about 20 miles back in the mountains. No details could be obtained, but the specimens seemed to indicate that they had come from rather small veins. As a guide could not be obtained and there were no trails, the deposit was not visited. RIVERSIDE COUNTY. About 3£ miles south of Winchester, in a hill rising about 650 feet above the surrounding valley, intrusives, now changed largely to ser- pentine, have been thrust into biotite schist standing on edge and having a general northwesterly strike. The limits of the serpenti- nous bodies are rather vague, but the masses are probably several hundred feet thick. Pegmatite dikes, carrying tourmaline, cut both schist and serpentine. The dikes range in thickness from 4 inches to a number of feet, and where they cut the serpentine chlorite is developed for a distance of 2 to 6 inches on each side. At several places along the schist-serpentine contact radial asbestos of a poor quality has been formed through a thickness of 6 to 8 feet. Narrow veins of fibrous asbestos are developed along a vein of magnesite a few inches thick in a tunnel about 70 feet long, which was run into the hill in search of gold. At a number of places in the serpentine trenches have been dug exposing magnesite stockworks with veins ranging in thickness from 2J inches down to those too small to be readily noticeable. (See PI. VIII, A.) From the best exposure, near the top of the lull, a piece of magnesite 6 inches thick, 18 inches wide, and 3 feet long was said to have been taken out, and was the largest piece found. In general the veins at this point are from one-half inch to 2 inches thick, with local enlargements. The distance between veins ranges from 3 to 10 inches. The magnesite itself is spongy and porous. U. S. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. VIII A. STOCKWORK OF MAGNESITE VEINS 3£ MILES SOUTH OF WINCHESTER. B. SHEETED SERPENTINE CONTAINING THIN VEINS OF MAGNESITE, NEAR DEER CREEK, TULARE COUNTY. RIVERSIDE AND OTHER COUNTIES. 89 A partial analysis of the magnesite by P. H. Bates, of the United States Geological Survey, is as follows : Partial analysis of maynesite from hill near Winchester. Silica (Si0 2 ) 4.73 Alumina (Al 2 0 3 ) 12 Ferric oxide (Fe 2 0 3 ) 08 Lime (CaO) 43 Magnesia (MgO) 44. 77 Carbon dioxide (C0 2 ) 49.40 99. 53 The lime is fairly low and there is little iron, but the silica is high. A company has been formed to work the magnesite, but that these deposits can compete with larger ones turning out as good or better rock in other parts of the State seems doubtful. In a well bored in the valley about a mile northwest of this deposit a magnesite vein 20 inches thick is said to have been struck. It was supposed by some that there must be a connection between this vein and the other deposits, but there is no ground for this belief, and such a connection is altogether unlikely. THE SIERRA NEVADA OCCURRENCES. KERN COUNTY. Magnesite is said to exist in Walkers Pass, in the Sierra Nevada, east of Bakersfield, but the deposits are so far from railway transportation that they are not now of economic importance. A specimen seen at Bakersfield was solid and of good white color. TULARE COUNTY. White River deposits.-— Ye ins reaching 6 inches in thickness are re- ported to occur along White River, 4 or 5 miles west of Tailholt, but none of workable size are knowm. Deer Creek deposits . — On and near the top of a serpentine hill about 1 mile south of the schoolhouse at Simmon’s ranch, about 8 miles southeast of Porterville, there are a great number of comparatively thin veins of magnesite. The hill is a portion of the outside range of foothills, in front of which lie two or three smaller hills, also of serpentinized rock. In one, directly in front of the magnesite de- posits and about 1 mile west, chrysoprase veins are being mined. A similar occurrence of chrysoprase veins in serpentine containing mag- nesite has been noted at Frankenstein, Silesia.® Veins of chalcedony up to 3 inches thick, showing greenish tints, occur near the magnesite veins. The country rock is a dull brown serpentinized peridotite a Squire, Lovell, Some observations on the magnesite of Silesia: Trans. Royal Geol. Soc. Cornwall, vol. 9, pt. 1, 1875, pp. 59-70. 40 MAGNESITE DEPOSITS OF CALIFORNIA. similar to that near Porterville. (See below.) As in the Porterville area, the rock is sheeted in places and contains great numbers of per- pendicular thin parallel veins of magnesite, not over an inch thick and about an inch apart. Crossing the perpendicular veins at a small angle are a second series of veins, and a third series crosses at right angles. (See PL VIII, B.) The veins are probably due to shearing, which produced cracks. These cracks then formed chan- nels for surface waters, and were filled by magnesite derived from the decomposition of the inclosing rock and brought by the waters from a distance and precipitated. Some, but not many, of these veins reach 2 feet in thickness for short distances; generally they are dis- continuous and irregular. A small amount of magnesite of excellent quality has been mined on the west side of the hill from a nearly vertical vein running paral- lel to the course of the hill and ranging from 10 to 18 inches in thick- ness. A specimen obtained on the top of the hill was partly analyzed by P. H. Bates, of the United States Geological Survey, with the follow- ing result: Partial analysis of magnesite from Deer Creek , Tulare County. Silica (Si0 2 ) - - - 0. 31 Alumina (A1 2 0 3 ) 11 Ferric oxide (Fe 2 0 3 ) 08 Lime (CaO) 24 Magnesia (MgO) 47. 22 Carbon dioxide (C0 2 ) 51. 64 99.60 . This is an excellent magnesite, the total impurities amounting to less than 1| per cent, but on the other hand the veins are small. The deposit is not more than 3 or 4 miles from the railroad, and may at some time pay to work. On the east side, near the top of a somewhat higher hill adjoining this one on the south, other small deposits of magnesite occur. Sev- eral short veins up to 2 feet thick were seen. Another 30 inches thick is said to be located not far from the saddle between the hills. Porterville deposits . — In the outer range of foothills, about 4 rniles northeast of Porterville, magnesite veins stand out prominently on two rounded hills at the top of smooth, steep slopes, rising about 1,000 feet above the town. One of the hills, which will be referred to as the northern hill, runs a little east of north, and the other, which will be referred to as the eastern hill, about N. 60° E. At their junc- tion is a saddle about 300 feet below the summits. The hills are free from brush or trees, and the broad San Joaquin Valley flattens smoothly away, so that the white veins standing above the surround- ing rocks attract attention from considerable distances. W. P. Blake, U. S. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. IX A. AMPHIBOLITE DIKE CUTTING THROUGH FLAT VEIN OF MAGNESITE. 4 MILES NORTHEAST OF PORTERVILLE. Small magnesite veins have formed in the amphibolite. B. CRUSHED MAGNESITE VEIN, 2 FEET WIDE, NEAR FURNACE 4 MILES NORTHEAST OF PORTERVILLE. TULARE COUNTY. 41 who passed through this region with the United States expeditions making explorations and surveys for a railroad in 1853, briefly de- scribed the deposits in his report. 0 Mining did not begin, however, until 1901, since when it has been carried on continuously. From 1902 up to the present time the mining has been done by the Wil- lamette Pulp and Paper Company, which controls under lease the northern hill and the w^est end of the eastern hill. Charles S. Harker is the owner of both hills and still retains control of the larger part of the eastern hill. The veins occur in a brown serpentinized perido- tite, having an apparent bedded' structure. The serpentine forms part of a metamorphic complex consisting of a small amount of fine- grained quartzite, amphibolite schist, serpentine, and other magnesian rocks, some of which are talcose and mica bearing. The rocks have a general northerly strike, with a- rather high (60°) easterly dip. They are cut off by a granitic mass on the south, a few hundred feet from the deposits. (See fig. 21.) Several granitic dikes cut the ser- pentine and other rocks, but do not cut the magnesite veins, though basic dikes (amphibolites) of several varieties cut both the country rock and the veins and are here and there squeezed to schist. Faulting is common,' but does not divide the serpentine into the small irregular blocks which result, in the serpentines of the Coast Range and many others, from the swelling of the rock as it changes its chemical and mineralogical form. However, movement is evi- dent, and the magnesite is invariably crushed in the larger veins. In one vertical 2-foot vein a couple of hundred feet southeast of the kiln (PI. IX, B) the magnesite has been so squeezed that it is left in irregular fragments whose sides are covered with abrasion lines, the whole looking as if at the time of crushing it had been in a semi- plastic state. In other veins the planes along which the magnesite has moved on itself are smooth and shaped so as to somewhat re- semble the curve of a highly arched shell. Along many of these planes is a bright red stain of iron oxide, although the surrounding magnesite is pure white. In other places the magnesite has evidently been crushed almost to a powder and recemented. It seems probable that the movements which have caused so much crushing and distortion have been due to other causes than the serpen tinization of the peridotite, for, as stated, it is not badly shattered, nor does it show the great number of smooth faces, due to small internal movements, that are common under such circumstances. The movements here may have been due to the stresses occasioned by the raising of the Sierra Nevada, to the intrusion of the granite or the amphibolites, or to all of these causes. a Blake, W. P., Itinerary, or notes and general observations upon the geology, mineralogy, and agricultural capabilities of the route: Report of explorations in California, for railroad routes to con- nect with the routes near the 35th and 32d parallels of north latitude, Washington, 1856, p. 28. 42 MAGNESITE DEPOSITS OF CALIFORNIA. Thin, nearly parallel veins of magnesite, mostly but a small fraction of an inch thick and hut little farther apart, occupy zones in the serpentinized rock in which the sheeting due to shearing and crushing is especially prominent. These zones are practically vertical. The rocks have been fissured by faulting in many directions, and in the fissures magnesite veins have been deposited. Two of the largest veins occupying such spaces are practically flat. The veins range in thickness from threadlike seams to 8 feet, and the principal vein, which occurs in the northern hill (PI. X, A), has been exploited through the hill, a distance of 785 feet, and can probably be followed through the valley between the hills and into the eastern hill. On the Fig. 2. — Plan of magnesite veins and workings 4 miles northeast of Porterville, Cal. northern hill this vein ranges in thickness from 2 to 8 feet; it cuts the lull near the south end (see PL X, A, and fig. 2), strikes north- west, and dips steeply to the northeast. An amphibolite dike 2 to 3 feet thick has been intruded into the serpentine near the vein and follows it for a short distance. Along this stretch the vein has been squeezed to a schist; at other places it is comparatively fresh. About 100 feet from the southeastern outcrop of the vein it is joined by another vein of about the same thickness, having a strike of N. 10° W., which has also been mined. At the north end of the hill are two “blanket” or flat veins. The largest one (PI. X, B) is practically horizontal in the middle part and NORTHERN HILL AT WILLAMETTE PULP AND PAPER COMPANY’S MAGNESITE MINE NEAR PORTERVILLE, LOOKING NEARLY NORTH. A, Nearly vertical vein; 11, Lower " blanket ” vein. The lower line ascending toward the right is a tramway; the upper one is a wagon road. TULAKE COUNTY. 43 somewhat uplifted at both ends — north and south. It extends through the hill, a distance of 362 feet, and is probably longer than broad, and from 2 to 4 feet or more thick. A basic dike flattens and spreads under a large part of the vein in a thin sheet 1 to 2 feet thick; then, breaking through (PL IX, A), it overlies the remainder of the vein. Thin magnesite veins fill cracks in the dike, but the mass of the vein is cut by it. It is probable that small veins, similar to those in the dike, are being formed all through the hill at the present time. There is nothing to show that the vein has been tilted from a more upright position to its present place, and it was evidently formed as it lies, flat and cutting across the vertical structure of the serpentine. This is accounted for by supposing that there was a slow movement in the rocks along this plane at the time of the vein’s deposition, the magnesite filling uneven open spaces along the horizontal fault, and that when there was another movement these deposits held the mass apart and made room for contiguous deposits. The crushed condition of the whole mass and the presence of inclusions of serpentine in lines approximately parallel to the sides of the vein give this hypothesis some color. The other “ blanket” vein lies above the north end of the vein just described. It dips at a rather low angle and will probably be found to run into the lower one. Adjacent to all the larger veins are many small reticulated veins ranging up to 3 or 4 inches in thickness. At the north end of the deposits is a stockwork of small veins 2 to 6 inches thick (PI. XI, A)f and it is thought that it may pay to blast the whole mass and hand pick it. Between the blanket veins and the large vertical vein are a number of smaller veins, from the outcrops of which some hundreds of tons of magnesite can probably be broken. At the north end of the hill, below the blanket veins, there is also a considerable stockwork of veins which can probably be worked by blasting and hand picking. On the west end of the eastern hill there are several veins of magne- site reaching a thickness of somewhat more than 3 feet, from which a small amount of magnesite has been mined. W. P. Bartlett, the superintendent for the Willamette Pulp and Paper Company, has developed an excellent system of stoping the vein standing at a high angle. He first ran a tunnel through the hill, along the vein, somewhat less than 100 feet below the top. He then began to break down the magnesite from the roof at the farther end of the tunnel, allowing the waste to accumulate, so that the face of magnesite, which constantly retreats toward the portal of the tunnel, could be reached from the debris slope, down which the magnesite was rolled and removed in cars from the foot. This proc- ess is shown diagrammatically in fig. 3. The magnesite was entirely 44 MAGNESITE DEPOSITS OF CALIFORNIA. removed from above this level, and the same system is being worked on the level below, which is even with the tramway, and when this is worked out probably a still lower level may be worked on the same vein. Either underhand or overhand stoping, whichever is at the time more advantageous, can be carried on by this system. The blanket veins require the removal of some waste rock, as the veins are not thick enough (from 2 to 4 feet) to permit economical working by mining out the magnesite alone. The waste is piled in the spaces already mined and forms a partial support for the roof. The roof is good and almost no timbering is required. A small amount of work has been done on some of the smaller veins, both on the northern hill and on the west end of the eastern hill. Practi- cally all of the magnesite mined is calcined, and a tramroad, laid on such a grade that the cars run down by gravity, is built along the Fig. 3. — Diagram showing mode of working a highly inclined magnesite vein at Willamette Pulp and Paper Company’s mine near Porterville, Cal. east side of the northern hill, through the saddle, to the kiln, which is located near the west base of the eastern hill. The veins are fortunately so situated that the tramway runs just under the blanket veins while maintaining its grade through the saddle. The kiln is located below the tramroad, so that the magnesite is dumped into a long chute through which it slides into the top of the kiln. (See PI. XI, B, and fig. 4.) The magnesite is broken by hand at the tunnels to lumps 4 inches or less in diameter. Crude oil is used for fuel, and the magnesite gradually rises in temperature as it moves from the top downward through the kiln, until it reaches the flame from the burners. It is then raised to a white heat, and kept there for twenty to twenty-five minutes, when it is withdrawn from below. It is said that after this treatment 3 to 5 per cent of carbon dioxide still remains in the material. The air for the burners passes through the withdrawn material and is thus considerably heated. U. S. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. XI A. OUTCROP OF STOCKWORK OF VEINS AT NORTH END OF WILLAMETTE PULP AND PAPER COMPANY'S DEPOSITS NEAR PORTERVILLE. Broken magnesite ready for calcining in foreground. B. FURNACE FOR CALCINING MAGNESITE AT WILLAMETTE PULP AND PAPER COMPANY’S MAGNESITE MINE NEAR PORTERVILLE. TULARE COUNTY. 45 Porterville, Cal. 46 MAGNESITE DEPOSITS OF CALIFORNIA. The following analyses of magnesite from this hill are at hand: Analyses of magnesite from hill 4 miles northeast of Porterville. 1 . 2. Silica (Si02> 2.28 0.90 Altunina (AI 2 O 3 ) .03 Ferric oxide ^Fe 2 Os) .26 J - .49 Lime (CaO) A. 'A 1.32 1.49 44.39 50.06 Magnesia (MgO) 45. 17 Carbon dioxide (CO 2 ) 50. 74 Water and undetermined 2. 57 99.80 99.90 1. Collected by the writer from tunnel No. 1 (in the large, highly inclined vein), and analyzed by A. J. Peters, of the United States Geological Survey. 2. Collected by W. P. Bartlett and analyzed by Abbot A. Hanks, of San Francisco, Cal. The lime in these samples is probably too high to allow a good cement to be made, but as the operating company uses practically the entire product in wood-pulp whitening and digestion at its Oregon mills, this impurity is not particularly obnoxious. In general the magnesite is white, but here and there it contains films of chlorite or serpentine where crushed. At other places there is a red stain of iron oxide on the surface of faces that have slipped on each other. Certain faces have been thinly coated with quartz, and one such face in which shrinkage cracks affect the quartz also is shown in PI. VI, B. The capacity of the furnace is from 27 to 29 tons of magnesite per day, giving 13 to 14 tons of magnesia. All shipments are made from Hilo spur, 1 mile north of the Porterville station. On the eastern hill there are a large number of magnesite veins of dimensions similar (except in length, in which they are probably deficient) to those on the northern hill. The total amount of mag- nesite is probably considerably less; as already stated, one vein may be the extension of the main vein cutting the northern hill. No such flat veins as those described on the northern hill are to be seen here. In places the veins contain a considerable amount of serpentine in fine particles, and elsewhere the serpentine contains sufficient mag- nesite to give it a gray appearance. A small amount of magnesite has been removed by open excava- tions and shipped by Charles S. Harker, the owner, to Oakland for the manufacture of carbon dioxide. Deposits on South Fork of Tule River . — In a high hill on the south- west side of South Fork of Tule lliver are a large number of magnesite veins with outcrops ranging in thickness up to 20 feet. The mag- nesite veins seen are on the north side of the hill in secs. 30 and 31, T. 22 S., R. 29 E. They are less than a mile south of Success school- house and about 9 miles from the railroad at Porterville. Should TULARE COUNTY. 47 active work be undertaken, the road could probably be somewhat shortened. The haul is almost entirely down hill. An electric road from Porterville to Springville, which has been under contemplation for some time, if built, would pass within 3 miles of the deposits. As Success schoolhouse is the most readily identifiable object in the landscape, the directions used in this description will be given with reference to it. The portions of the hill containing the magnesite are composed of a rock much more completely serpentinized than that nearer Porter- ville. In the sections examined there are only scattered fragments of original minerals, probably pyroxenes, locally in radial crystals, which, in the hand specimen, reach 2 inches in length. At the foot of the hill S. 26° W. (magnetic) from Success school- house, a magnesite vein outcrops along the edge of the narrow flood plain of the river. The outcrop is from 3 to 10 feet thick, and is exposed prominently for a distance of about 500 feet, running north- westward, parallel to the river. In this distance it rises from the level of the flood plain to 60 feet above it at the southeast end. What is apparently the end of the outcrop, however, may be only the point to which it has been covered by debris from the hill slope, and at the other end it may run for some distance beneath the covering of soil. At each end, however, is a small watercourse, and in ser- pentine areas such channels very commonly mark fault lines. The magnesite is generally of a good white color, but is here and there grayish. In places the vein contains horses of serpentine, and at one place it is cut by a fine-grained basic dike, which is composed mainly of light-green amphibole and a fresh plagioclase feldspar with much magnetite, and which for most of the distance that it is visible runs approximately parallel to the vein. On the assumptions that 5 feet is the average thickness of the vein and that it extends for 100 feet into the hill — both of which premises seem wholly reasonable — the vein would contain 500 (length) X 5 (thickness) X100 (depth) =250,000 cubic feet, which, on the basis of 11 cubic feet per short ton, is equivalent to about 22,700 tons. A partial analysis of magnesite from this vein, made by A. J. Peters, gave the following result: Analysis of magnesite from hill south of Success schoolhouse, Tulare County. Silica (Si0 2 ) 0.80 Alumina ( A1 2 0 3 ) 42 Ferric oxide (Fe 2 0 3 ) 20 Lime (CaO) 1.02 Magnesia (MgO) 45.94 Carbon dioxide (C0 2 ) 51.30 99.68 48 MAGNESITE DEPOSITS OF CALIFORNIA. The total impurities here amount to nearly 2.5 per cent, of which about 1 per cent is lime. There is probably enough lime to make it undesirable for the manufacture of cement, but it is a good material for use in paper, gas, or brick making. * The serpentine is in places full of thin parallel veins of magnesite, similar to those at the deposits near Porterville and Deer Creek. A couple of hundred feet above and west of the northwest end of the large vein just described are a large number of irregular magnesite nodules and masses, from which probably several hundred tons could be blasted at small cost. In the same neighborhood there are a num- ber of smaller veins. About 200 feet (barometric measurement) above the flat vein is a fairly continuous outcrop reaching possibly 20 feet in thickness and 200 feet in length, in which the magnesite is of a beautiful pure-white color, but there are many inclusions of serpentine. At a point S. 17° W. (magnetic) of Success schoolhouse and about 800 feet (barometric) above the river is a vein from 2 to 6 feet wide, which may be followed for about 200 feet. The strike is northwest- ward, with a high northeasterly dip. On the top of the hill, at an altitude of over 1,000 feet above the river, are a number of veins ranging up to 6 feet in thickness, but most of them can not be traced far. One vein, averaging between 2 and 3 feet in thickness, was followed for 250 feet, and with greater care it may be possible to trace it farther. These veins are nearly a mile south of the flat vein first described, and in the intervening space are hundreds of irregular veins, which measure up to a foot or even more in thickness and which, in places near the river, form stockworks that could be blasted and hand picked at small expense. The belt of serpentine carrying the magnesite has been crushed and sheeted in a northwesterly direction, and probably owes this structure to the forces that acted similarly on the magnesite-bearing serpentines nearer Porterville, which lie about 6 miles northwest. No develop- ment work has been done on these deposits. ° Round Valley deposits . — On the east side of the mouth of Pound Valley, between 3 and 4 miles east of Lindsay, a number of magnesite veins ranging up to 2 feet in thickness crop out on the southwestern face of the hill, between 150 and 450 feet (barometric) above the floor of the valley. The country rock is serpentine, similar in macroscopic appearance to that at Porterville. The belt in which the veins occur has a northwestern trend similar to that of the deposits on South Fork of the Tule and of those near Porterville. The lower veins are of poor quality, as they contain a considerable amount of serpentine. The upper veins appear to be of good quality, but all are thin and too far a Since this paper went to press word has been received from Mr. W. P. Bartlett that he is now shipping magnesite from these deposits. TULARE COUNTY. 49 apart to be worked economically from the same opening. Hauling to the Southern Pacific Railroad at Lindsay would be easy and on down grade all the way. Deposits near Exeter . — Magnesite had been reported to the writer as occurring in a number of the orange orchards east of Exeter, where it was said to be killing the trees, but in each case the substance was found to be carbonate of lime. However, on the southwest spur of Rocky Hill, 2 miles east of Exeter, there are a few small veins of magnesite about 500 feet above the valley. The largest vein is not more than a foot wide, and most of them are only from 1 to 3 inches wide. The area over which the veins occur is very small and the deposits are without economic value. A vein of califomite, a variety of vesuvianite, occurs alongside the magnesite. It is said to have been worked under the supposition that it was impure chrysoprase. From the matter thrown out the vein appears to be from 2 to 4 inches wide. The rock in the shaft was so much shattered and coated with calcareous material that the vein could be but imperfectly made out. The color of the califomite is rather irregular; the ground color is a light green, carrying a hint of yellow, but through this are sprinkled small spots of buff or white, and spots about one sixty-fourth of an inch across of dark green. Deposits of magnesite were reported in the Yokohl Valley, a few miles east or southeast of Exeter, but they could not be definitely located. Naranjo deposits . — George D. Ward, of Oakland, is interested in some small deposits of magnesite about 7 miles northwest of Lemon Cove and 1 mile northwest of Naranjo post-office. The deposits are situated in a serpentine hill containing many intrusions of greenstone and granite. Most of the veins are from 2 to 5 inches thick and are exposed for only a few feet. They are in general of rather pure- looking but spongy material though some have considerable serpentine mixed with them. The largest vein is situated on the north side of the hill and is but 16 inches thick. A small excavation has been made, and this affords the only exposure. The vein is much crushed and the magnesite appears to be of only fair quality. At a number of places on the hill are veins, 1 to 2 inches thick, of translucent white nonprecious opal. Other Tulare County deposits . — Small veins of magnesite are reported to occur near Auckland, but they are probably of little importance. There are undoubtedly other veins, which may or may not be of value, in the great areas of serpentine that lie along the foothills of the Sierra Nevada through the entire length of the county. 51136— Bull. 355—08 4 50 MAGNESITE DEPOSITS OF CALIFORNIA. FRESNO COUNTY. Nine miles east of Sanger George D. Ward has located magnesite claims on both sides of Kings River, near what is known as Red Hill. The country is one of rather high, smooth, nearly treeless hills, rising perhaps somewhat over 1,000 feet above the river. The rocks are metamorphic and include some serpentine and partially serpentinized tuff. They are all in comparatively narrow bands, and, except the serpentine, are gneissoid. Much of the rock was originally granite or diorite. All the rocks have a structure much resembling bedding. The amount of magnesite in sight seems, at first glance, remarkably large for the amount of serpentine present. On the north side of the river the principal vein is on what is known as the Snow Cap claim. The vein outcrops about half a mile from the river, in a small embayment in the hills. A face has been exposed showing the magnesite to be at least 8 feet thick. (See PL XII, B.) It has a strike of N. 24° W. (magnetic) and an easterly dip of about 75°, which probably agree with the strike and dip of the country rocks. On the foot wall is a considerable amount of soft, friable magnesite, which is very much like calcareous tufa and which is, in fact, a magnesian tufa. This deposit is more than a foot thick. About 3 feet from the foot wall is an irregular vein of magnesite, from 6 inches to 3 feet thick, which probably joins the main vein a short distance below, and which could be economically mined with it. The vein can be definitely followed for about 600 feet to the north, across a low hill, and seems to get thinner toward the farther end. The magnesite is a clear white, containing serpentine only here and there. A partial analysis of a specimen of fine-grained pure-white mag- nesite from the body of the vein, collected by the writer and analyzed by A. J. Peters, was as follows: Analysis of magnesite from large vein, Snow Cap claim, Kings River. Silica (Si0 2 ) 0.20 Alumina ( A1 2 0 3 ) 04 Ferric oxide (Fe 2 0 3 ) 12 Lime (CaO) 96 Magnesia (MgO) 46.48 Carbon dioxide (C0 2 ) 51.80 99. 60 It will be noticed that there is nearly 1 per cent of lime in the specimen, although a commercial analysis made for Mr. Ward was said to show none. A quarter of a mile north from the end of the vein, along the same strike, is a vein of rather impure magnesite. The dip is shallower and it is not likely that the two veins are connected. U. S. GEOLOGICAL SURVEY BULLETIN NO. 355 PL. XII A. MAGNESITE VEIN ON SOUTH SIDE OF KINGS RIVER, 9 MILES EAST OF SANGER. B. MAGNESITE VEIN ON SNOW CAP CLAIM, NORTH SIDE OF KINGS RIVER, 9 MILES EAST OF SANGER. /, FRESNO AND OTHER COUNTIES. 51 A couple of hundred feet up the ridge, west from the main outcrop of the Snow Cap, is a magnesite vein of good quality from 10 to 21 inches wide, which may be followed for 100 to 150 feet. It is on the Snow Cap claim. On the same claim, in the gulch on the south, 200 feet from the main outcrop of the Snow Cap and just below an old wagon road, a mass of fine white magnesite showing a surface of 8 by 13 feet has been uncovered. At the time of visit not enough work had been done to show whether the occurrence was a vein or a large nodule. On the Governor claim, a quarter of a mile S. 16° W. from the main Snow 'Cap outcrop, across a gulch and about 100 feet (baro- metric measurement) above the Snow Cap, is a small outcrop of a magnesite vein of good quality, dipping highly S. 60° E. It is prob- ably 2 feet thick and has been exposed- for a length of 10 feet. Mag- nesite float, which has been found 300 feet or more to the southwest, has been supposed to come from the extension of this vein, but there is nothing at present shown to prove it. Besides the vein mentioned there are at a number of places smaller veins, largely of noncompact magnesite. The surfaces of the spongy magnesite are colored a fine pink. Small red lichens grow upon the magnesian rocks of this vicinity, and if treated with an alkali (sodium hydrate or ammonia) they give the same pink hue, so that the color may be derived from these lichens, or it may be due to some iron compound. No other coloring material, such as cobalt or manganese, which would account for it could be detected in the specimens. On the south side of Kings River, about half a mile from and 650 feet above the stream, is a fine large vein of magnesite, which runs east and west across a northward-projecting hill. (See PI. XII, A.) The vein as exposed at the time it was visited was at least 8 feet wide and may have been somewhat wider. It could be readily traced for about 200 feet, but no attempt had been made to show its length by excavations, so that it may prove to extend farther. The magnesite seemed to be of good quality, with but few inclusions of serpentine. The deposit is reached by a fairly easy grade and could be very economically worked. The haul from the deposits on both sides of the river to the railroad at Sanger is all downhill except for trifling grades, and in general the roads are excellent. The magnesite from the two sides would, however, have to go by different roads, owing to the difficulty of fording the river. MARIPOSA AND TUOLUMNE COUNTIES. Large bodies of magnesite containing green mica and pyrite have occasionally been reported from Mariposa and Tuolumne counties, but probably most if not all of the deposits referred to are dolomite con- 52 MAGNESITE DEPOSITS OF CALIFORNIA. taming large amounts of mariposite, a chrome mica. There are in these counties, however, belts of serpentine in which it would not be surprising to find magnesite, though the writer’s inquiries have so far located none. PLACER COUNTY. Damascus deposits . — Many statements have been published from time to time heralding the deposits near Damascus as “the largest in the State,” possibly because they are among the least convenient to reach. The writer did not visit the locality, as at the time he was in this portion of the State the deposits were reported to be covered with snow. The magnesite is in the S. \ sec. 18, T. 15 N., R. 11 E., 3 or 4 miles from Damascus and Michigan Bluff and probably not more than 10 miles in a direct line from Colfax. The following inf ormation was kindly furnished by Mr. Harold T. Power, of Bullion, Cal., and Mr. H. W. Turner, formerly of the United States Geological Survey, but now of Portland, Oreg. In the southwest quarter of the section the deposits are located just below the Morning Star ditch, in a serpentine country rock. Besides a number of small veins an inch or so in width, there are sev- eral lenses of magnesite forming practically one body about 30 feet in width and 100 feet long, which contains some serpentine. A spec- imen sent in by Mr. Power is of good appearance, though not very compact. As no analysis has been made, its composition can not be given. A small exposure of a 2-foot vein is said to occur in the southeast quarter of the section. The country is so rough that under present conditions the mag- nesite can not be mined at a profit. A lumber railroad has been surveyed to run close to the deposits, and should such a road be built they might be worked. W. P. Bartlett, of Porterville, reports a 2-foot vein of magnesite in the canyon of American River, near this place, but on account of its unfavorable location it is valueless. Other small veins also have been reported, but so far nothing of value has been found. MAGNESITE DEPOSITS IN OTHER COUNTRIES. It is always desirable to know something of mineral deposits which may be possible or certain competitors in any mining or quarrying enterprise. California’s commercial isolation from the eastern portion of the United States, caused by the long railroad hauls, precludes railroad shipment of products that sell as cheaply as magnesite. Owing, however, to the possibility of shipping by water with a fair margin of profit, the following notes on competing foreign deposits are MAGNESITE DEPOSITS IN OTHER COUNTRIES. 53 NORTH AMERICA. CANADA. Quebec . — Magnesite occurs at a number of places in the Dominion of Canada, but the deposits known seem to be remarkably different from those of California. In eastern Canada magnesite has been found in the township of Grenville, Argenteuil County, Quebec,® in place and in loose bowlders, some of the latter weighing many tons. In appearance this magnesite is granular and much like clear, rather coarse grained marble, and it is supposed to be of sedimentary origin. One outcrop is about 100 feet wide and a quarter of a mile long. If it is a sedimentary deposit it is unique, so far as has come to the atten- tion of the writer, as nowhere else are magnesian sediments known in which the percentage of magnesium carbonate present exceeds to any appreciable degree the theoretical amount contained in dolomite (45.65 per cent). Although limestones carrying any percentage of magnesium carbonate up to 45.65 may be found, the remainder of the series between 45.65 and 100 per cent have had no representatives until the discovery of these deposits. Analyses by the Geological Survey of Canada of various specimens showed magnesium carbonate, 49.71 to 95.50 per cent; calcium carbonate from a “very small amount” to 30.14 per cent; and magnesia other than carbonate (probably nearly all serpentine), 3.08 to 9.17 per cent. An average of 57 samples from another locality gave — Average composition of magnesite from Quebec. Magnesium carbonate 81. 27 Calcium carbonate 13. 64 Magnesia other than that present as carbonate 3. 66 98.57 British Columbia . — In the Atlin district of British Columbia, at the town of Atlin , h deposits of hydromagnesite (3 MgC0 3 .Mg (HO) 2 + 3H 2 0) occur in Pine Creek valley as a line white powder covering several acres and known to be as much as 5 feet deep. The deposits are evidently derived from springs, the waters from which carry 1.834 parts of magnesia in 1,000. Hydromagnesite when pure carries 43.9 per cent of magnesia, 36.3 per cent of carbon dioxide, and 19.8 per cent of water. Similar deposits 0 occur at the 108-mile House on the Cariboo road a Hoffman, G. C., Report of the section of chemistry and mineralogy: Ann. Rept. Geol. Survey Canada, vol. 13 (for 1900), pt. R, 1903, pp. 14-19. 6 Gwillim, J. C., Report on the Atlin mining district, British Columbia: Ann. Rept. Geol. Survey Canada, vol. 12, pt. B, 1899, pp. 47-48. c Hoffman, G. C., Report of section of chemistry and mineralogy: Arm. Rept. Geol. Survey Canada, vol’. 11, 1900, pp. 10-11. 54 MAGNESITE DEPOSITS OF CALIFORNIA. 93 miles north of Ashcroft, Lillooet district, British Columbia, where they are scattered over 50 acres or more of ground. At three or four places patches of the material 50 to 100 feet wide stand afoot or more above the general surface. At one point a shaft showed the deposit to be over 30 feet thick. At Atlin an exceedingly impure magnesite occurs with serpentine and dunite, a and is said to be over 1,000 feet wide on the Anaconda group of claims. It is impregnated with iron pyrites, and is cut by apple-green quartz carrying 1 pennyweight of gold per long ton and 15 per cent of nickel. A partial analysis of the magnesite is as follows : Partial analysis of magnesite from Atlin, British Columbia. Magnesia (MgO) 21. 70 Protoxide of iron (Fe 2 0 3 ) 5. 10 Carbonic acid (C0 2 ) 27. 00 Silica (Si0 2 ) 45. 68 Combined water and loss 0. 52 100. 00 Under present conditions these British Columbia deposits are probably without economic value. MEXICO. Lower California . — On the island of Santa Margarita, in Magdalena Bay, extensive deposits of magnesite have recently been examined by Julius Koebig, of Los Angeles, for a firm of that city. The country rocks are said to be sandstone, quartzite, and syenite. No mention is made of more magnesian rocks, though it seems highly probable from the amount of magnesite described that such rocks are present. The island is mountainous and is 25 miles long by 4 or 5 miles broad. Doctor Koebig says in his report : Practically every canyon of the Sienite Mountains, by decomposition of the eruptive rocks, shows larger or smaller deposits covering in some instances the entire surface of hills and mountain sides. The banks of the canyons, where the rocks have been cut by the streams during the rainy season, show magnesite strata several feet thick, and for a distance of a few hundred feet to over a mile the arroyo itself contains large quan- tities of magnesite in the shape of bowlders, weighing from a few pounds to 3 to 5 tons apiece. * * * Estimated in the most conservative way, I have seen actually in sight on the surface, and in no case more than H miles from shore, 300,000 to 500,000 tons ready to be picked up and packed to the beach without the use of any tools other than a sledge hammer. * * * For labor there are plenty of Mexicans to be had at not to exceed $1.50 Mexican per day. * * * As means of transportation to the wharf there are 300 or more donkeys on the island. * * * There is plenty of water for a crew of Mexicans and the pack animals. a Gwillim, J. C., op. cit., pp. 21-22. MAGNESITE DEPOSITS IN OTHER COUNTRIES. 55 The following analyses are given in the report : Analyses of magnesite from Santa Margarita Island , Lower California. 1. 2. Insoluble, sand and clay Trace. } 0.21 .43 0.06 .10 Trace. Ferric oxide (Fe203> Alumina (AI2O3) Carbonate of lime (CaCOs) Lime (CaO) Carbonate of magnesia (MgCOs) 99. 36 Magnesia (MgO) 99.05 1. Raw magnesite; analyst unknown. 2. Calcined magnesite; analysts, Baverstock & Staples, Los Angeles, September 13, 1907. The company offers to furnish the magnesite for $3.50 f. o. b. vessel at Santa Margarita. Other deposits of magnesite are reported from various parts of Mex- ico, but little is known of them. SOUTH AMERICA. VENEZUELA. The Venezuelan Government has recently granted for twenty-five years the exclusive privilege a of exporting magnesite found on private lands on the island of Margarita, to a company which expects to ship from 12,000 to 15,000 tons annually. Nothing further is known of the deposits. Dana 6 quotes N. S. Manross as stating that magnesite occurs near Mission Pastora, in Canton Upata. EUROPE. AUSTRIA. Styria in Austria has very large deposits of magnesite which are actively worked. The largest company is the Veitscher Magnesit- werke Actiengesellschaft, c with mines at Veitsch, 5 miles from the Mittersdorf Murzthal railway station. During 1903 this company produced 71,016 tons of magnesite and shipped to the United States 35,000 tons of the calcined product. This company and the Magnesite Company, Limited, of Hungary, have a working agreement. d a Moffat, T. P., Daily Consular and Trade Repts., No. 3108, Washington, February 25, 1908, p. 8. &Dana, E. S., Descriptive mineralogy, 6th ed., New York, p. 275. c Rublee, W. A., Daily Consular Repts., No. 2276, Washington, June 6, 1905, p. 2. d Private letter. 56 MAGNESITE DEPOSITS OF CALIFORNIA. HUNGARY. The Magnesite Company, Limited,® with headquarters at Nyustya, Gomor County, is the largest company operating in Hungary. The veins worked are very large, ranging from 150 to 300 feet in width, and are worked as open quarries, with stages from 40 to 60 feet high. The magnesite is yellowish or bluish white, in some places fine grained and in others of very coarse crystalline structure. The following analyses of the magnesite, of which No. 2 is calcined, are given as representative : Analyses of Nyustya magnesite. 1 . 2. Silica (Si02) . 0. 74- 0. 76 .39- .27 3. 27- 3. 43 1.20- .90 44. 80-45. 00 50. 10-50. 20 1.67 3. 47 4.68 2. 94 86.90 Alumina (AI2O3) Ferric oxide (Fe20 3 ) Lime (CaO) Magnesia (MgO) . ... . Carbon dioxide (CO 2 ) The output of dead-burned magnesite of the company in 1904 (1905?) was 22,000 to 23,000 tons from Nyustya and 11,000 to 12,000 tons from Jolsva and Ochtina. The company was at that time mak- ing 750,000 magnesite brick per year. The production of magnesite in Hungary during 1907 was as fol- lows: 6 Production of magnesite in Hungary, 1907. Quantity. Value. United Magnesite Company, Nyustya Quintals. 98,000 1,090 1,126 Crowns. 519,000 1 Company of Magnesite-Industry: Nyustya (Gomor) Jolsva (Gomor) 1 10,877 Martonbaza * 437 General Magnesite Company, Hizsnyo (Gomor) 78,000 330,000 178,653 859,877 The product is equivalent to 19,693 short tons, valued at $174,554. The whole output was made into brick. Besides brick and calcined magnesite, the Hungarian companies ordinarily make “ caustic” or partly calcined magnesite for use as a mortar, with which magnesite brick are set. GERMANY. Deposits of magnesite were worked for many years in the neighbor- hood of Frankenstein, Silesia. 0 The magnesite is said to occur in a Private letter. b Letter from director substitute, Mining Dept., Royal Hungarian Geol. Inst., April 24, 1908. c Squire, Lovell, jr., Some observations on the magnesite of Silesia: Trans. Royal Geol. Soc. of Corn- wall, vol. 9, pt. 1, 1875, pp. 59-70. MAGNESITE DEPOSITS IN OTHER COUNTRIES. 57 “nests/’ probably similar to what are called “ bowlders” in California; that is, in large nodules. The deposits are covered- with soil, and the peasants dig at random for it. The analysis was given as follows : Analysis of magnesite from Frankenstein, Silesia. Silica (Si0 2 ) 5.60 Alumina (A1 2 0 3 ) ’.85 Calcium carbonate (CaC0 3 ) 40 Magnesium carbonate (MgC0 3 ) 93.00 99.85 As would be expected from the lack of iron or other coloring matter, the magnesite is said to have been very white. It is not known whether the deposits are still worked. Some chrysoprase was found in veins close by. GREECE. The principal magnesite deposits of Greece are located on the island of Euboea.® The Anglo-Greek Magnesite Company, Limited, operates magnesite quarries belonging to the Galataki monastery, 10 miles from the port of Limni, whence the magnesite is shipped. The output of this company during 1902 and 1903 was as follows: Magnesite output of Galataki quarries and exports to the United States, 1902 and 1903. [Short tons.] Raw magnesite. Caustic calcined magnesite. Dead- burned magnesite. Output. Exported to the United States. Output. Exported to the United States. 1902 14.600 26, 300 6,647 '3,200 3.500 3,550 578 1903 125 1,200 The Society of Public Works of Athens is exploiting magnesite de- posits by underground workings at Mantudi and Limni. During 1902 it shipped to the United States 7,390 metric tons of magnesite and 92 tons of firebrick; in 1903, 2,335 tons of magnesite; in 1905, 22,747 tons of magnesite; and in 1906, 32,194 tons of magnesite, which was produced at Mantudi . b The total output for Greece in 1905 c was 47,849 short tons, and in 1906, 71,015 short tons, valued at $168,376 and $283,333, respectively. Magnesite is also found at Xirochori, on the island of Euboea; near Mariki, close to Thebes (Bceotia); and at Hermioni, in Argolis. a McGinley, Daniel E., Daily Consular Reports, No. 2276, Washington, June 6, 1905, pp. 3, 4. b Bergbau in Griechenland: Zeitschr. angew. Chemie, vol. 21, January 31, 1908, p. 225. c Quoted “from a Government report” in Min. Jour. (London), vol. 82, 1907, p. 633. 58 MAGNESITE DEPOSITS OF CALIFORNIA. Analyses of fused Grecian magnesite from unknown mines gave Fitzgerald & Bennie a the following figures: Analyses of Grecian magnesite ( mines unknown). ITALY. Magnesite occurs at Casellette, in the Val di Susa, and at several other places in the Turin district, and on the island of Elba. None of the deposits seem to be of very large size. During 1906 the Turin district produced 1,463 short tons of raw magnesite , b valued at $3,958, and 220 tons of calcined magnesite, 0 valued at $2,180. The Casellette deposits d consist of great numbers of roughly parallel small veins up to a few inches thick, in a serpentinized lherzolite. They are close enough together so that the rock can be broken down and hand picked. No production was reported from the island of Elba, though the deposits have been worked in former years. The deposits are stock- works of small veins 0 in a serpentinized lherzolite and are appar- ently similar to those at Winchester, Cal. (See p. 38.) The fol- lowing analyses of the Elba magnesite are given by D’Achiardi: Analyses of magnesite from the island of Elba.f Water (H 2 0) at 110° C 1. 82 2. 28 Water (H 2 0) above 110° C 1. 68 2. 08 Carbon dioxide (C0 2 ) 44.70 43.86 Silica (Si0 2 ). 8.15 8.65 Alumina (A1 2 0 3 ) 1 Trace .10 Ferric oxide (Fe 2 0 3 ) / Lime (CaO) 3.50 .99 Magnesia (MgO) 40.84 42.05 100. 69 100. 01 MACEDONIA. Magnesite is found in large quantities ^ in Macedonia near the coast, not far from the Greek border. Some of the veins stand out a Physical properties of fused magnesium oxide: Trans. Am. Electrochem. Soc., vol. 9, 1906, p. 102. b Rivista del Servizio Minerario, 1906, Roma, 1907, p. xlix. cOp. cit., p. liii. d Piolti, Giuseppe, Sull’ origine della magnesite di Casellette (Val di Susa): Mem. della Accad. scr Torino, 2d ser., vol. 47, pp. 126-142. e D’Achiardi, G., La formazione della magnesite all’ Isolad’ Elba: Atti (Mem.) Soc.toscana sci. nat., Pisa, vol. 20, 1904, pp. 86-134. /D’Achiardi, G., op. cit., pp. 123, 129. g Der Bergbau in Mazedonien: Montan Zeitung (Graz, Austria), vol. 15, January 1, 1908, p. 10. MAGNESITE DEPOSITS IN OTHER COUNTRIES. 59 like walls and may be seen from the sea. Little work has been done on them, but in 1906 a new mine on the Chalkidike Peninsula began operations, and a furnace was put up. a NORWAY. Magnesite is being mined from deposits in Norway at Snarum, * 6 in the Modums division of Buskerud bailiwick, on the Kroder line, a spur of the Drammen Randsfjord line, 56 kilometers (35 miles) from Drammen, the nearest city and port. The magnesite is found in serpentinized olivine rocks which occur with schists and quartzites. Some of it is crystallized in rhombohedra, but such deposits are generally small. The main deposits are ordinarily granular. In both forms the magnesite is nearly pure white, though the granular magnesite contains some serpentine, which occurs in more or less dis- tinctly marked bands or in grains up to the size of a bean, rather evenly distributed through the mass. The included serpentine is used to sinter the material in burning the brick. There are two principal fields — the Dvbingdals, 3 miles north of Snarum station, and the Langerud field, 1J miles west of Snarum station. In the former the magnesite area covers about 1,200 square meters. The veins average about 13 feet in width, and dip 30° and upward. They are worked by underhand stoping. In the Langerud field magnesite is exposed for 135 feet along Snarum or Hailing River, and also 100 yards farther southwest. There are also smaller de- posits in the neighborhood of these fields. A factory, which has a capacity of about 2,500 tons of brick per year, is operated near Snarum. The magnesite is sold calcined or as brick. An analysis of the brick is as follows : Analysis of magnesite brick made at Snarum , Norway. Silica (Si0 2 ) 9.3 Manganous oxide (MnO) 05 Aluminum sulphate (A1S0 4 ) 2. 00 Iron oxide (Fe 2 0 3 ) 4. 60 Phosphoric anhydride (P 2 0 5 ) 046 Sulphur (S) 003 Lime (CaO) 00 Magnesia (MgO) - 83. 600 Loss by heating .50 100. 099 The magnesite is remarkable in that it shows no lime. According to tests quoted in the article referred to, brick from the Snarum factory are more heat resistant than the Austrian Veitsch brick. “The mineral wealth of Macedonia: Mining Jour. (London), vol. 83, 1908, p. 251. 6 Daumann, E., Magnesitfran Snarum: Bihang till Jern-Kontorets Annaler for 1905, Stockholm, 1905, pp. 222-235. 60 MAGNESITE DEPOSITS OF CALIFORNIA. During 1907 a the output of the works was 900 tons of calcined magnesite, valued at $12,060, and 125 tons of brick, valued at $3,685- RUSSIA. Magnesite occurs in Russia in the Uphim Mountain district of the Urals, and during 1906 one firm, the Magnesite Company, produced 26,320 tons of magnesite . b AFRICA. TRANSVAAL. Extensive deposits of magnesite occur between Kaapmuiden and Malelane, 2 miles south of the Pretoria-Delagoa Bay Railway, 87 miles from Louren^o Marquez and 300 miles from Johannesburg. The magnesite is found in a great number of veins, ranging up to 4 feet in thickness, and has been exploited to a depth of 95 feet. c Most of the veins are much thinner than the limit of width given, but there seems to be a large area of serpentine carrying thejn. The serpentine is here 3 miles wide. Some of the magnesite is soft and powdery, like that at Red Mountain, Santa Clara County, Cal. (p. 35). One 4 to 6 inch vein d is described as “ entirely of pure, glassy- looking magnesite.” Hall gives the following analysis of a picked specimen from these deposits: Analysis of magnesite from Malelane, Transvaal. Magnesia (MgO) 45.272 Carbon dioxide (C0 2 ) 49. 80 Silica (Si0 2 ) 2.30 Lime (CaO) Ferric oxide (Fe 2 0 3 ) 80 Moisture at 110° C.. 16 98. 332 Quartz forming thin coatings on the magnesite is found at various places. The rock is used for making carbon dioxide, and much of it is calcined by producer gas at about 1,100° C. and mixed, either in lump or ground, with magnesium chloride imported from Germany to make oxychloride cement. Most of the output goes into this product, for which its freedom from lime makes the material par- ticularly well suited. a Letter from Dr. Johan H. L. Vogt, professor of metallurgy at the University of Kristiania, Feb- ruary 15, 1908. b Magnesite and chrome iron ore in the Urals: Mining Jour. (London), vol. 82, December 14, 1907, paragraph on p. 721. cllall, A. L., The magnesite deposits of Malelane: Rept. Geol. Survey, Transvaal Mines Dept., for 190(3, Pretoria, 1907, pp. 127-132. d Hall, A. L., op. cit.,pp. 128-129. For further reference to the Malelane deposits see Hollis, W. S., Magnesite deposits in South Africa: Daily Consular Repts., No. 2276, Washington, June 6, 1905, pp. 7-8; Praagh, L. V., The Transvaal and its mines, London and Johannesburg, 1906, pp. 633-634. MAGNESITE DEPOSITS IN OTHER COUNTRIES. 61 OTHER AFRICAN DEPOSITS. Henry W. Nevinson ° speaks of “the volcanic district of North Bihe, with its boiling springs and great deposits of magnesia.” The Bihe region is a couple of hundred miles east of Benguela, in Portu- guese West Africa. No further details are given, but the association with boiling springs suggests that such a magnesian deposit would probably be hydromagnesite, similar to the deposits in British Columbia. (See p. 53.) “Magnesia,” 6 by which magnesite is probably meant, is reported to occur in Mashonaland, near the western side of Africa, notably at Umtali and at the great Zimbabwe ruins — at the latter place in steatite. ASIA. INDIA. Madras . — Magnesite is found at a number of places in India, the most important of which seems to be in the Chalk Hills, 4 miles northwest of Salem, Madras Presidency, in the southern part of the Indian Peninsula. The magnesite here occurs in interlacing veins, some of which stand several feet above the surrounding talcose, serpentinized, and other magnesian rocks. From the whiteness of the outcropping magnesite the name “Chalk Hills” has been given to the range. The main magnesite deposits occur over an area of 10 square miles, c and there are various outlying deposits. During 1905 the production was 2,035 tons of magnesite, valued at $2,750, and during 1906 1,832 tons, valued at $2,440/ Mysore . — Magnesite deposits occur at a number of points near Mavinhalli and Kadakola, in Mysore/ in the south-central part of the Indian Peninsula. The deposits do not seem to be of commer- cial importance at present, though the magnesite has been used locally as a substitute for lime/ There are also reported to be many deposits of magnesite in the neighborhood of Yelwal/ but their extent is unknown. Ceylon . — “Hydromagnesite does not occur in commercial quanti- ties so far as known, but has some local use.” h a The slave trade in Africa: Harper’s Magazine, vol. 112, December, 1905, p. 116. &Swan, Robert M. W., Notes on the geography and meteorology of Mashonaland, in Bent, J. T. Rained cities of Mashonaland, London, 1892, p. 347. c King, W., jr., and Foote, R. B., On the geological structure of the districts of Triehinopoly, Salem, and South Arcot included on sheet 79 of the Indian atlas: Mem. Geol. Survey India, 1865, pp. 312-327. d Dennison, E. Haldeman, Daily Consular Repts., No. 3138, Washington, March 31, 1908, pp. 1-2. « Primrose, A., Notes on magnesite in the Mysore district: Rec. Mysore Geol. Dept., vol. 4 (1904?). pp. 147-157. /Op cit., p. 151. 9 Ram, B. Jaya, Summary of the work done during the year 1904-5: Rec. Mysore Geol. Dept., vol. 6 (1906?), p. 52. ft Parsons, James, principal mineral surveyor for Ceylon, letter, March 5, 1908. 62 MAGNESITE DEPOSITS OE CALIFORNIA. AUSTRALIA. QUEENSLAND. In Queensland a magnesite occurs in the Normanton district in the Gulf country; in the Rockhampton district on Dinner, Sawpit and Stewarts creeks; at Stanwell, Islapot, Moonmera, and the Pointer, near Yamba. In other districts it occurs at Clermont, Toorwomba, Ipswich, Kilkivan, and Newellton. The deposit at Kilkivan is thought to be the largest, though all the deposits are so small that it is improbable that any of them can be worked commercially. NEW SOUTH WALES. Small deposits are known in New South Wales 6 in the diamond fields at Bingera, county of Murchison, and near Mudgee. At Two- mile Flats, near Mudgee, pebbles in waste heaps were cemented together by it. On Cudgebegong Creek it forms in peculiar vermicu- lar or wormlike forms. Other localities in New South Wales are Lochlan River, Mooly Gully, and Scone, county of Brisbane; Louisa and Lewis Pond creeks, county of Wellington; and Barraba, county of Darling. None of these deposits are of commercial value, but recently magnesite has been discovered in what appears to be con- siderable quantity c 3J miles northwest of Fifield. Over an area of 100 acres it crops out through red clay as large rounded blocks of pure -white material. It is said to be capable of yielding many thousand tons of magnesite at a cost not exceeding 38 cents per ton, on drays. A partial analysis of this magnesite is as follows: Partial analysis of magnesite from Fifield, New South Wales. Magnesium carbonate (MgC0 3 ) 99.01 Lime (CaO) Absent. Ferric oxide (Fe 2 0 3 ) , l ^ Alumina ( A1 2 0 3 ) / Gangue (sand) •. 42 SOUTH AUSTRALIA. 99.97 Large deposits are reported in South Australia, but so far no work has been done on them. TASMANIA. In Tasmania magnesite “occurs in serpentine, Parson’s Hood Mountain; in veins, Trial Harbor; Meredith Range; Dundas; Hazlewood. ” d a Dunstan, B., Magnesite in Queensland, quoted in Queensland Gov. Min. Jour. (Brisbane), vol. 8, August, 1907, p. 405. b Liversidge, Archibald, The minerals of New South Wales, 2d ed., Sydney, 1882, p. 176. c Jaquet, J. B., Magnesite at Fifield: Australian Min. Standard, vol. 38, 1907, p. 172. d Petterd, W. F., Minerals of Tasmania: Papers and Proc. Royal Soc. Tasmania, 1893, Hobart, 1894, p. 45. MAGNESITE DEPOSITS IN OTHER COUNTRIES. 63 OCEANICA. NEW CALEDONIA. Extensive deposits of magnesite occur on the north end of the west coast of New Caledonia,® at the contact of black schists with serpentine, particularly between Koumac and Voh. A specimen obtained near Koumac gave the following analysis: Analysis of magnesite from vicinity of Koumac , New Caledonia. Silica and insoluble (Si0 2 , etc.) 0. 8 Ferric oxide (Fe 2 0 3 ) 8 Lime (CaO) 3.3 Magnesia (MgO) 42.4 Carbonic anhydride (C0 2 ) 51.5 Moisture 4 99.2 It will at once be noticed that the lime content is too great to per- mit the use of the material in oxychloride cement. The freight is high from New Caledonia to Europe or America, so that the only exports have been a trial shipment of 42 tons in 1907. 6 a Glasser, Ed. M., Report a M. le ministre des colonies sur les richesses minerales de la Nouvelle- Caledonie: Ann. des mines, 10th ser., vol. 5, pt. 5, 1904, pp. 548-549. b Eng. and Min. Jour., vol. 85, February 1, 1908, p. 283, quoting from Bulletin du Commerce, Noumea, New Caledonia. INDEX. A. Page. Africa, magnesite deposits of 60-61 Alameda claim, description of 33-37 magnesite of, analysis of 36 Alameda County , magnesite deposits on 37 Alba levis, manufacture and use of 13 American Magnesite Co., deposits of 33-34 American River, magnesite deposits in 52 Arizona, magnesite in 7 Arnold, E. W., on Red Slide magnesite de- posits 26,27 Ashcroft, B. C., magnesite deposits near 54 Asia, magnesite deposits of 61 Atlin, B. C., magnesite deposits at 53-54 magnesite at, analysis of 53 Auckland, magnesite deposits near 49 Australia, magnesite deposits of 62 Austria, magnesite deposits in 55 B. Bakersfield, magnesite deposits near 39 Banta’s camp deposit, description of 37 Bartlett, W. P., on American River deposits. 52 Bartlett & Stanley, magnesite deposit of 29-31 magnesite of, analysis of 30 Bay Cities Water Co., deposits of 32-33 deposits of, structure of, plate showing. 32 Benguela, West Africa, magnesite deposits near 61 Blanco claim, description of 29-31 Brick, magnesia, manufacture of 11,12 British Columbia, magnesite deposits in 53-54 Brucite, precipitation by 20 C. Calcination, temperature of 9-10 California, magnesite deposits in 7-8 magnesite deposits in, detailed descrip- tions of 17-52 location of, map showing 7 production of 16 technology of 8-15 See also Magnesite. wages in 15 Cambria, magnesite deposits near 38 Canada, magnesite deposits in 53-54 Canada claim, description of 36 Carbon dioxide, manufacture and use of 8-9 Cazadero, magnesite deposit near, view of 20 Cement. See Oxychloride cement. Ceylon, magnesite deposits of 61 Chiles Valley, magnesite deposits in 29, 31 51136— Bull. 355—08 5 Page. Clay, magnesite weathered beneath, plate showing 20 Cloverdale, magnesite deposits near 21, 22, 24 Coast Range, magnesite deposits in 21-39 Cochrane, Mrs. A. F. magnesite deposit of. . . 33 magnesite of, analysis of 33 Conchoidal fracture, specimens showing, plate showing 8 Coyote, magnesite deposit near 31-32,37 magnesite near, analysis of 32 Creon deposit, analysis of 23 description of 22-23 Crucibles, magnesia, manufacture of 11-12 Cummings, Pat, magnesite claim of 24 D. Damascus deposits, magnesite of ’. 52' I Deer Creek deposits, analysis of 40 J description of 39-40 plate showing 38 Dike cutting magnesite, plate showing 40 E. East Austin Creek, magnesite deposits near. 26 Eckert ranch deposit, analysis of 23,24 description of 23-24 Elba, magnesite deposits of 58 magnesite of, analysis of 58 Electric furnace, use of 13 Epsom salts, manufacture of 7, 13 I Europe, magnesite deposits in 55-60 Exeter, magnesite deposits near 49 F. Field work, period of 8 Fitzgerald, A. J., on magnesia manufacture. . 12 Fitzgerald and Bennie, experiments by 14 Foreign countries, magnesite deposits in. . 7-8, 52-63 Fresno County, magnesite deposits in 50-51 Fusing point, determination of 14-15 G. Germany, magnesite deposits of 56-57 magnesite of, analysis of 57 Gilliam Creek, magnesite deposits on 24-25 magnesite from, analysis of 25 magnesite from, cost of 15 Goodwin and Mailey, experiments of 14 Governor claim, magnesite of 51 Greasy Camp Creek, magnesite deposit on 31 Greece, magnesite deposits of 57-58 magnesite of, analysis of 58 shipments of, to California 16 65 66 INDEX. H. Hall (George) ranch deposit, description of. . . Hixon ranch deposit, analysis of description of specimen of, view of view of Hungary, magnesite deposits of magnesite of, analyses of wages in I. Incandescent lamps, use of magnesia in India, magnesite deposits of Italy, magnesite deposits of magnesite of, analysis of K. Kern County, magnesite deposits in King claim, description of Kings River, magnesite deposits on magnesite on, analysis of cost of views of Kiser deposit, description of Koebig, Julius, on Lower California, magne- site L. Lamps. See Incandescent lamps. Lemora Cove, magnesite deposits near Literature, scantiness of Livermore, magnesite deposits near Lower California, Mexico, magnesite deposits in magnesite in, analyses of M. Macedonia, magnesite deposits of Madeira deposit, description of Madras, magnesite deposits of Magnesia brick, shapes, and crucibles, bind- ers for manufacture of. Magnesite, bowlders of bowlders of, view of calcination of character of cracks in, plate showing deposits of, in California, description of. . . in foreign countries, descriptions of . . . dike cutting, view of distribution of map showing formation of fusing point of importation of fracture of, plate showing manufacture of market for precipitation of production of properties of sintering of structure of, plate showing uses of Page. Magnesite, veins of, plates showing ... 20, 42, 44, 50 prominence of 18-19 weathering of 19 ; 34-35 plates showing 18,20 Magnesite Products Company, magnesite de- posits of 22 Magnesium, source of 15 Magnesium carbonates, uses of ' 13 Mammoth vein, description of 34 Map of California, showing magnesite deposits 7 Mariposa County, magnesite deposits of 51 7 52 Markets, data on 15-16 Maryland, magnesite in 7 Massachusetts, magnesite in 7 Matthai, Frank, magnesite deposit of 31 Mendocino County, magnesite deposits in 21-22 Mexico, magnesite deposits in 54-55 Morgan Hill, magnesite deposit near 33 Mysore, magnesite deposits of 61 N. Napa County, description of 28 magnesite deposits in 28-31 magnesite of, cost of 16 Naranjo, magnesite deposits near 49 Nevada, magnesite in 7 New Almaden, magnesite deposits near 37 New Caledonia, magnesite deposits of 63 magnesite of, analysis of 63 New South Wales, magnesite deposits of 62 magnesite of, analysis of 62 New York City, magnesite in, price of 16 North America, magnesite deposits in 53-55 See also California. Norton (Ed.) ranch, magnesite deposits on. . 28 Norway, magnesite deposits in 59-60 magnesite of, analysis of 59 O. Oakland, carbon dioxide made at. . : 8 magnesia brick plant at 11 Oceania, magnesite deposits of 63 magnesite of, analysis of 63 Oxychloride cement, manufacture and uses of 13-14 P. Pennsylvania, magnesite in • 7 Placer County, magnesite deposits of 52 Pope Valley, magnesite deposit in 28 magnesite deposit in, view of 20 Porterville, magnesite deposits near 39-46 magnesite deposits near, map of 42 section of, figure showing 43 views of 40,42,44 magnesite from, analyses of 4 cost of 15 specimens of, plate showing 22 Power, H. T., on Damascus deposits 52 Priest, D. C., magnesite deposit of 31 ' Q- Quebec, magnesite deposits in 53 magnesite of, analysis of 53 Queensland, magnesite deposits of 62 Page. 24 21 21-22 22 20 15,56 -56 15 15 61 58 58 39 37 50-51 50 ■ 16 50 38 54 49 8 33 54-55 55 58-59 25 61 12 11-13 20 20 9-10 8 22 17-52 52-63 40 7-8 7 17-18 14-15 16-17 8 8-15 15-16 ‘ 20 16 8 12-13 32 8-15 INDEX. 67 R. Page. Red Mountain, magnesite deposits at 33-37 magnesite at, analysis of 36 Red Slide deposit, analysis of ' 27 description of 26-27 Riverside County, magnesite deposits in 38-39 Round Valley, magnesite deposits in 48-49 Russell, E. T., magnesite deposit of 31 Russia, magnesite deposits of 60 Rutherford, magnesite deposits near 31 S. San Benito County, magnesite deposits in . . . 38 San Felipe Creek, magnesite deposit on 32 Sanger, magnesite deposits near 50 magnesite deposits near, view of . . 50 San Jose, magnesite deposits near 37 San Luis Obispo County, magnesite deposits in 38 Santa Barbara County, magnesite deposits in 38 Santa Clara County, magnesite deposits in . . 31-37 Santa Margarita, Mexico, magnesite deposits of 54-55 magnesite of, analyses of 55 Serpentine, decomposition of 18,19-20 description of 17 magnesite in 17 plates showing 20,38 occurrence of 17 Shrinkage, cracks in magnesite due to, view of 22 Sierra Nevada, magnesite deposits in 39-52 Snow Cap claim, magnesite deposit of 50-51 magnesite deposit of, view of 50 magnesite of, analysis of 50 Snowflake claim, description of 29-31 Soda Creek Canyon, magnesite deposit in 31 Sonoma County, magnesite deposits in 22-28 magnesite of, analyses of 23, 24, 25, 27 cost of 16 Sonoma Magnesite Co., magnesite deposits of. 26 magnesite deposits of, view of 20 South Africa, cement making in 13 magnesite deposits of 60 magnesite of, analysis of 60 South America, magnesite deposits of 55 South Australia, magnesite deposits of 62 Spinks, C. H., on Red Mountain deposits 35 Page. Stanislaus County, magnesite deposits in 34,37 Success schoolhouse, magnesite deposits near. 46-48 magnesite near, analysis of 47 T. Tailholt, magnesite deposits near 39 Tasmania, magnesite deposits of 62 Transvaal, magnesite deposits of 60 magnesite of, analysis oT 60 Tubing, magnesite, uses for 14 Tulare County, magnesite deposits in... -. 3y-49 Tule River (South Fork), magnesite deposits on 46-48 magnesite on, analysis of 47 Tuolumne County, magnesite deposits of 51-52 Turner, H. W., on Damascus deposits 52 V. Van Hise, C. R., on derivation of magnesite. . 18 Veins, magnesite, depth of 18-19 description of 20 prominence of 18-19 Venezuela, magnesite deposits of 55 W. Walkers Pass, magnesite deposits in 39 Walters deposit, description of 28-29 view of 20 Ward, G. D., magnesite deposit of 50 Watts, O. P., on magnesia crucibles 11-12 Weathering, effect of, plate showing 18 West Africa, magnesite deposits of 61 Western Carbonic Acid Gas Co., magnesite deposit of 25 plant of 8 diagram of 9 White River deposits, description of 39 White Rock deposit, description of 28-29 Willamette Pulp and Paper Co., magnesite deposit of 41 magnesite deposit of, views of ' 2 , 44 plant of, figure showing 45 view of 44 Winchester, magnesite deposits near 38-39 magnesite near, analysis of 39 view of 38 Y. Yokohl Valley, magnesite deposits in 49 DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR Bulletin 356 GEOLOGY OF THE GREAT FALLS COAL FIELD MONTANA BY CASSIUS A. FISHER WASHINGTON GOVERNMENT PRINTING OFFICE 1909 CONTENTS. Page. Introduction 7 Literature 7 Topography 14 Relief 14 Drainage 16 Missouri River 16 Sun River 17 Smith River 17 Belt Creek 18 Other small streams 19 Culture 20 Descriptive geology 21 Stratigraphy 21 General outline 21 Sedimentary rocks 24 Carboniferous system 24 Madison limestone 24 General statement 24 Castle limestone 24 Quadrant formation 25 Character and extent 25 Age 27 Jurassic system 27 Ellis formation 27 Character and extent 27 Fossils 28 Morrison shale (?) 28 Character and extent 28 Fossils 30 Cretaceous system 30 Kootenai formation 30 General statement 30 Character and extent 31 Fossils 33 Colorado shale 36 General statement 36 Character and extent 36 Fossils 38 Tertiary and quaternary systems 39 Terrace gravel 39 General statement 39 Character 39 Mode of occurrence 39 Origin of terraces 40 Age 40 3 4 CONTENTS. Descriptive geology — Continued. Stratigraphy — Continued. Sedimentary rocks — Continued. • Tertiary and quaternary system — Continued. Page. Glacial deposits 41 General statement 41 Drift 41 Lake sediments 42 Alluvium 43 General statement 43 Character and extent 43 Dune sand 43 Character and extent 43 Source 44 Igneous rocks 44 Metamorphic rocks 46 Structure 47 Plains province 47 General conditions 47 ' Domes 48 Faults 49 Little Belt Mountains 49 High wood Mountains 50 Economic geology 50 General statement 50 Coal 50 Geological occurrence 50 Sand Coulee area 51 Location and extent 51 Character and thickness of coal bed 52 Development 53 Belt Creek mines 54 General statement 54 Mines operated 54 Anaconda Copper Mining Company mine 54 Schmauch mine 57 Millard mine 57 Richardson mine 57 Orr mine 57 Abandoned mines 58 Hill mine 58 Buzzo or Hill mine 58 Boston and Montana mine 58 Herman & Powell mine 59 Watson mine 59 Brady mine 59 American Smelting and Refining Company's mine 59 Prospects 60 Entry prospects 60 Diamond-drill prospects 60 Sand Coulee mines 60 General statement 60 Mines operated 61 Cottonwood Coal Company mine 61 CONTENTS. 5 Economic geology — Continued. Coal — Continued. Sand Coulee area — Continued. Sand Coulee mines — Continued. Mines operated — Continued. Pa s e - Nelson mines 63 Gerber mine 64 Mount Oregon Coal Company mine 64 Dahn mine 65 Brown mine 65 Stainsby mine 65 Abandoned mines 66 Smith River mines 66 General statement 66 Mines operated 66 Carville mine 66 Gibson mine 67 Patterson and Rice mines 67 Bickett mine 67 Love mine 67 Prospects 68 Otter Creek area 68 Location and extent 68 Character and thickness of coal bed 69 Development 69 General statement 69 Mines operated 70 Nollar mine 70 Chamber Brothers’ mine 70 Nullinger mine 70 Abandoned mines 71 Sage Creek area 71 Location and extent 71 Character and thickness of coal bed 72 Development 73 General statement 73 Mines operated 73 Schultz mine 73 Seman mine 74 Hughes mine 74 Abandoned mines 75 Corwin & McGregor mine 75 Fisher mine 75 West Fork of Willow Creek mine 75 Sage Creek Sheep Company mine 75 Prospects 76 Entry prospects 76 Diamond-drill prospects 77 Character of coal 77 General statement 77 Physical properties 77 Chemical properties ; 79 Future development 81 Timber 82 Index 83 ILLUSTRATIONS. Page. Plate I. Geologic map of the Great Falls region, Montana In pocket. II. Map of the Great Falls region, Montana, showing coal lands 7 III. Dry bed of Belt Creek near Belt, Montana 18 IV. Columnar sections showing stratigraphy along Belt Creek -valley, Montana 20 V. Madison limestone overlain by shale of the Quadrant formation, near Riceville, Montana 24 VI. Basal Jurassic sandstone lying unconformably on Madison limestone, near Stockett, Montana 28 VII. Columnar sections showing stratigraphy in different parts of Great Falls region, Montana 30 VIII. Sections of coal in Belt Creek and Smith River districts, Montana. . 54 IX. Anaconda Copper Mining Company’s coal plant at Belt, Montana. . . 56 X. Sections of coal bed in Sand Coulee district, Montana 60 XI. A, Cottonwood Coal Company’s mine No. 5, near Stockett, Montana; B, Nelson coal mine and plant at Sand Coulee, Montana 62 XII. Sections of coal bed in Otter Creek and Sage Creek areas, Montana.. 70 Fig. 1. Ideal cross section, showing relations between the two lake deposits in Missouri River valley west of Great Falls 42 2. Ideal longitudinal section, showing the relation of the two lake de- posits shown in fig. 1 to the drift dam and the ice dam 43 6 'Ll'C’.'J BULLETIN NO. 356 Pl_ MAP OF THE GREAT FALLS REGION, MONTANA, SHOWING COAL LANDS. nr PL. II MAP . 17 N. GEOLOGY OF THE GREAT FALLS COAL FIELD, MONTANA. By Cassius A. Fisher. INTRODUCTION. This report is the result of field studies made during the season of 1906. It is designed mainly to furnish information regarding the character and extent of £he coal resources of the Great Falls region. It includes a description of the rock formations, indicating their character, distribution, structure, and stratigraphic relations, and also a brief statement of mineral resources other than coal. The region under consideration comprises 1,500 square miles, situated mainly in north-central Montana, and extending along the base of the Rocky Mountain front range from a point 10 miles west of Judith River to a short distance beyond the Missouri. The location and orographic relations of the field are shown in the index map on PI. I (in pocket). The field lies principally in Cascade County, but includes portions of Fergus and Chouteau counties, having as its boundary on the south the Big and Little Belt mountains and on the north the Great Plains and the High wood Mountains. Throughout the work the author was assisted by II. M. Eakin, who mapped portions of the area, measured many sections, and assisted in compiling the results for publication. Assistance in the field was also rendered by W. R. Calvert, J. D. Pollock, A. J. Hazlewood, and D. E. Winchester, and the author is indebted to S. B. Robbins, project engineer of the Sun River reclamation project, and to O. C. Mortson, formerly county surveyor of Cascade County, for valuable information placed at his disposal in connection with the preparation of the work. LITERATURE. The western half of the area here described as the Great Falls coal field has never been systematically studied by previous workers in geology, but several reports dealing with the general geology of dif- ferent parts of the district to the east in the vicinity of the Highwood and Little Belt Mountains have been published. 7 8 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. The Great Falls of Missouri River, also the Giant Springs, are phenomena which have attracted widespread attention since the earliest explorers followed up the course of the Missouri to the north- west, and a number of descriptions of them have been published. Those appearing first set forth mainly the size and beauty of these falls, but later, as the region was settled and the town of Great Falls promised to become an important industrial center, a number of articles dealing with their utility were published in technical journals. Captain Lewis, of the Lewis and Clark expedition, which was made in 1804-1806, was the first to give an accurate account of the Great Falls and Giant Springs, and to describe certain features of the geog- raphy of the region bordering this portion of Missouri River. It is probable that other early explorers were attracted by the Great Falls and mentioned their occurrence and surroundings in describing the Northwest Territory. The coals have been the subject of much of the geologic literature concerning this region, and many, if not most, of the more important geologic discoveries have been made in connection with a study of the nature and extent of these deposits. The investigations of the geologists of the Hayden and Transcontinental surveys in this part of the United States were confined mainly to the region lying east of Great Falls, and did not extend into the western part of the field. In 1880 W. M. Davis published an article a in which he gave an account of the geology of the Little Belt and Highwood mountains and the ad- joining plains. During the same year George H. Eldridge described the geology of the Great Falls coal field. The next observer in the field was J. S. Newberry, who, in connection with an investigation of the surface geology of the country bordering the Northern Pacific Railroad, including the Great Falls coal field, discovered fossil plants associated with the coals, which established the Kootenai age of these deposits. After this discovery articles were published by Newberry and Fontaine dealing especially with the age of these coal-bearing rocks, as determined from their fossil floras, and their correlation with Kootenai rocks of other localities in the United States and Canada. In the spring of 1891 W. II. Weed, of the United States Geological Survey, while making a general study' of the coal fields of Montana, visited this region and later described the coal deposits in considerable detail. The Geological Survey has published an annual account of coal operations in this field since 1888, and also a number of general reports on the coals of Montana and the Rocky Mountain region which have dealt principally with the production of this im- portant coal field. The first systematic work in this field was done in 1893-94 by W. H. Weed, assisted by L. V. Pirsson. In their published report 6 a Relation of the coal of Montana to the older rocks: Tenth Census U. S., vol. 15, 1880, pp. 697-712. b Highwood Mountains of Montana: Bull. Geol. Soc. America, vol. 6, 1894-95, pp. 389-422. LITERATURE. 9 the topographic and geologic features, structure, and characteristic rocks of the different eruptive centers of the Highwood Mountains and vicinity are discussed at considerable length. In 1899 the Fort Benton folio, a which includes the eastern part of the area described, and the Little Belt Mountains folio, 6 which treats of the area adjoining on the south, both by Mr. Weed, were published by the Geological Survey. During the past few years the glacial geology of this por- tion of Montana has been described by Warren Upham c and by F. H. H. Calhoun. d Since the Government irrigation project has been undertaken in Sun and Teton valleys, a number of scientific and popular articles have appeared dealing principally with the surface waters of the district. In 1906 an investigation of the underground waters of this general region was made by the writer, the results of which will soon be published by the Geological Survey. The following bibliography contains the titles of the more important geologic papers dealing with this region, arranged in chronologic order: Lewis and Clark Expedition, 1804-1806 (Coues, 4 vols., 1893). An account of the journey up the Missouri from St. Louis to the Rocky Mountains, thence to the Pacific coast. Contains description of the region bordering on the Mis- souri in the vicinity of Great Falls, Mont. The falls of the Missouri were measured and described; also brief mention made of the Giant Springs. Hayden, F. V., Geologic report of the exploration of the Yellowstone and Missouri rivers, U. S. War Dept., pp. 85-94. 1860. Contains a chapter on the geology from Wind River Mountains to Fort Union on Missouri River. Gives description of a trip down Smith River and past the falls of the Missouri to Fort Benton, etc. Includes geologic map of the area. Williams, Albert, Jr., Mineral Resources U. S. for 1883-84: U. S. Geol. Survey, pp. 52-55. 1885. The Montana coal fields are described briefly, and their area is estimated. Newberry, J. S., Surface geology of the country bordering the Northern Pacific Railroad: Am. Jour. Sci., 3d ser., vol. 30, pp. 337-347. 1885. Includes a brief description of the surface geology in the vicinity of Great Falls, Mont., with special reference to glacial drift. Lindgren, Waldemar, Eruptive rocks: Tenth Census U. S., vol. 15, pp. 719-737. 1886. The igneous intrusions of the Little Belt and Highwood mountains are described; also the dike near Sun River, including its character and mode of occurrence. Davis, W. M., Relation of the coal of Montana to the older rocks: Tenth Census U. S., vol. 15, pp. 697-712. 1886. Includes a description of the geology of the Little Belt and Highwood mountains and the plains region from Fort Benton up Missouri and Sun rivers. Eldridge, G. H., Montana coal fields: Tenth Census U. S., vol. 15, pp. 742-751. 1886. Treats of the coals along Belt Creek, Sand Coulee, and Deep Creek (Smith River), giving a section of the geologic formations at Belt Butte, near Belt. The coals of the Sage Creek area are described as a part of the Judith Basin coal fields. ® Geologic Atlas U. S., folio 55, U. S. Geol. Survey, 1899. b Geologic Atlas U. S., folio 56, U. S. Geol. Survey, 1899. c Outer glacial drift: Am. Geologist, vol. 34, 1904, pp. 151-160. d Montana lobe of the Keewatin ice sheet: Prof. Paper, U. S. Geol. Survey No. 50, 1906. 10 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. Day, David T., Mineral Resources U. S. for 1885: U. S. Geol. Survey, pp. 36-39. 1886. Brief reference is made to the coal production of the Belt and Sand Coulee mines. Day, David T., Mineral Resources U. S. for 1886: U. S. Geol. Survey, pp. 262-288. 1887. Eldridge is quoted in reference to the extent and character of Montana coal fields. (See Eldridge.) The production of the Great Falls region is given. Newberry, J. S., The Great Falls coal field: School of Mines Quart., vol. 8, No. 4, p. 327. 1887. Gives evidence as to the geologic age of the coal-bearing rocks in the Great Falls region, correlating them with the Kootenai formation of the Lower Cretaceous of Canada. Chamberlin, T. C., Rock scorings of the great ice invasions: Seventh Ann. Rep. U. S. Geol. Survey, p. 77. 1888. Discusses local “mountain wash” from High wood Mountains, etc. Mortson, 0. C., and Ashburner, Chas. A., Mineral Resources U. S. for 1888: U. S. Geol. Survey, pp. 34-35, 289-292. 1890. Describes the occurrence, extent, and chemical character of iron ores in the vicinity of Great Falls, Mont., pp. 34-35. Also refers to coal areas and operations in north- central Montana, pp. 289-292. Swallow, G. C., Report of the Montana inspector of mines for the six months end- ing November 30, 1889, pp. 43-51. Contains reports on various coal fields in Montana, including those of Cascade County. Analyses of Sand Coulee coal are given and comparison made with eastern coking coals. Estimates of the amount of coal in Cascade County are given. Swallow, G. C., Report of the Montana inspector of mines, 1890. Includes reports on various coal fields in Montana, making brief mention of those in Cascade County. Newberry, J. S., Flora of the Great Falls coal field: Am. Jour. Sci., 3d ser., vol. 41, pp. 191-201. 1891. Describes briefly the general geology of the Great Falls region, and gives detailed description of fossil plants collected near the mouth of Sun River, Montana. Parker, E. W., Mineral Resources IT. S. for 1889-90: U. S. Geol. Survey, pp. 228-231. 1892. The coal product of Montana is treated by counties and the amount applied to various uses is also shown. List is given of producing mines of the Great Falls region. Sand Coulee mine is largest producer. Contains analysis of Sand Coulee coal. Parker, E. W., Mineral Resources U. S. for 1891: U. S. Geol. Survey, pp. 269-270. 1893. The production of Montana coal mines, including those in the Great Falls <.oal field, is referred to briefly. Weed, W. H., The coal fields of Montana: Eng. and Min. Jour., vol. 53, pp. 520- 522, 542-543, 1892; vol. 55, p. 197, 1893. Describes the geologic occurrence of the coal beds and the character and extent of the coal deposits in various Montana areas, including Great Falls. Shoemaker, C. S., Report of the Montana inspector of mines. 1893. Includes reports on Cascade County coal mines. The equipment and output of Belt and Sand Coulee mines are treated on page 33, and they are described and a statement of their production given on page 86. Weed, W. H., Two Montana coal fields: Bull. Geol. Soc. America, vol. 3, pp. 301- 330. 1892. Abstract: Am. Geologist, vol. 11, pp. 181-182. 1893. Describes the general geology of the Great Falls coal field, giving information con- cerning the character and extent of the coals. The age of the. coal-bearing rocks is also discussed. LITERATURE. 11 Wilson, H. M., American irrigation engineering: Thirteenth Ann. Rept. U. S. Geol. Survey, pt. 3, pp. 371-386. 1893. The proposed irrigation system of the Sun River valley and the adjacent region is fully described, and the rainfall, topography, and amount of reclaimable land is dis- cussed. Parker, E. W., Mineral Resources U. S. for 1892: U. S. Geol. Survey, pp. 436-438. 1893. The coal production of Montana is given by counties, and classified as to varieties — bituminous, semibituminous, and lignite. Fontaine, W. M., Description of some fossil plants from the Great Falls coal field of Montana: Proc. U. S. Nat. Mus., vol. 15, pp. 487-495. 1893. Gives a description of the general character of the flora, its age, and the character- istics of several new species. Parker, E. W., Mineral Resources U. S. for 1893: U. S. Geol. Survey, pp. 320-322. 1894. The coal output of Montana is given by counties. Reference is made to the increased activity over previous years. Parker, M. S., Water power of the falls of the Missouri, Great Falls, Mont.: Eng. News, vol. 32, p. 44. 1894. The several falls of the Missouri are described, and estimates made of their water power. Makes reference to the Giant Springs and their effect on the river water. Weed, W. H., and Pirsson, L. V., High wood Mountains of Montana: Bull. Geol. Soc. America, vol. 6, pp. 389-422. 1895. Describes the topographic features, geologic structure, and characteristics of the rocks of each eruptive center of the High wood Mountains. Reference is also made to the coal at Belt, Mont., its thickness, character, and age. Parker, E. W., Sixteenth Ann. Rept. U. S. Geol. Survey, pt.,4, pp. 144-148. 1895. The coals of Montana are discussed and reference is made to their geologic age. The bituminous and lignitic fields are differentiated. Production by counties is given. Parker, M. S., The Great Falls watey power: Eng. Rec., vol. 31, No. 16, pp. 274- 275. 1895. Gives brief description of the various falls of the Missouri near Great Falls, Mont., with illustrations of the power plant at Black Eagle Falls. Shoemaker, C. S., Report of the Montana inspector of mines, 1895. Includes reports of various coal fields in Montana, their production, etc. Cascade County mines are treated on p. 42. Parker, E. W., Seventeenth Ann. Rept. U. S. Geol. Survey, pt. 3, pp. 454-458. 1896. A condensed report on Montana coal production is included. Parker, E. W., Eighteenth Ann. Rept. U. S. Geol. Survey, pt. 5, pp. 551-556. 1897. A review including the coal production of Montana by counties, from 1889 to 1896, inclusive. Byrne, John, Report of the Montana inspector of mines, pp. 37-38. 1897. Includes reports on coal fields of Montana, and describes Belt and Sand Coulee mines. Parker, E. W., Nineteenth Ann. Rept. U. S. Geol. Survey, pt. 6, pp. 456-461. 1898. A brief review is given of production of coal in Montana, dating from 1889. The number of mines in each county (in 1896), their output, and various items of informa- tion regarding the production are included. Parker, E. W., Twentieth Ann. Rept. U. S. Geol. Survey, pt. 6, pp. 440-443. 1899. Cascade County is credited with two-thirds of the entire State coal production. Tables of coal production by counties are also included. Weed, W. H., Fort Benton folio, Montana: Geologic Atlas U. S., folio 55, U. S. Geol. Survey, 1899. 12 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. Describes the surface features, geology, structure, and history of the region. Treats in considerable detail the mineral resources, including coal, gold, and silver. Con- tains topographic, geologic, economic, and structural maps, also columnar sections. Parker, E. W., Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 6, pp. 468-471. 1900. Includes brief classified statistical tables of Montana coal production for 1898. States that a large proportion of coal is machine mined. Byrne, John, Report of the Montana inspector of mines: Twelfth Annual Report, pp. 53-54. 1900. Includes reference to workings and output of coal mines at Belt, Stockett, and Sand Coulee, Mont. Parker, E. W., Mineral Resources U. S. for 1900: U. S. Geol. Survey, pp. 406-408. 1901. Statistics are given of coal production in Montana for 1899. That of 1900 is stated to be the largest in the history of the State, amounting to 1,661,775 short tons; value $2,713,707. Sixty-three per cent of the total production was machine mined. Storrs, L. S., The Rocky Mountain coal fields: Twenty-second Ann. Rept. U. S. Geol. Survey, pt. 3, 1901, pp. 415-471. 1902. Includes discussion of the Montana coal fields, mentioning briefly the Great Falls coal field. Parker, E. W., Mineral Resources U. S. for 1901: U. S. Geol. Survey, pp. 401-403. 1902. Gives tables of Montana coal production. During 1901 the Sand Coulee mines were practically abandoned, decreasing the output of Cascade County 333,988 tons. Storrs, L. S., Eighth Rept. Montana Bureau Agr., Labor, and Industry, pp. 374- 382. 1902. Coal statistics for the State are given, and Storrs is quoted in reference to the extent and distribution of Montana coal fields. Willis, Bailey, Stratigraphy and structure, Lewis and Livingstone ranges, Montana: Geol. Soc. Am., vol. 13, pp. 305-352. 1902. Describes the physiography, the occurrence, and character of the Algonkian, Car- boniferous, Cretaceous, and Pleistocene formations, and the geologic structure of the general region. Parker, E. W., Mineral Resources U. S. for 1902: U. S. Geol. Survey, pp. 396-398. 1903. Tabulated statistics of Montana coal production are given. Rowe, J. P., Some Montana coal fields: Am. Geologist, vol. 32, pp. 369-380. 1903. Describes by counties the bituminous, semibituminous, and lignite coals of Montana, giving briefly their geologic age and distribution. Rowe, J. P., Some volcanic ash beds in Montana: Bull. Montana Univ. No. 17 (geol. ser., No. 1). 1903. Discusses the origin and physical and chemical properties of volcanic ash in Montana, describing by counties its characteristics, geologic position, and general distribution. A number of illustrations are introduced, showing the microscopic character of the volcanic ash, leaves found in the deposits, and thickness and character of beds. Parker, E. W., Mineral Resources U. S. for 1903: U. S. Geol. Survey, pp. 484-487. 1904. Contains brief review of coal-mining conditions in Montana as compared with pre- vious years, and gives statistics of the coal output of the State. Newell, F. IL, Third Ann. Rept. U. S. Reclamation Service, pp. 307-313. 1904. Discusses the proposed irrigation project of the Sun and Teton river district, and describes the water supply available from streams and storage reservoirs, also the ter- ritory which can be irrigated. Leiberg, J. C., Forest conditions in the Little Belt Mountains Forest Reserve, Mont., and the Little Belt Mountains quadrangle: Prof. Paper U. S. Geol. Survey No. 30, 1904. LITERATURE. 13 The surface waters of the region and their relation to agricultural, grazing, and forest lands are included in the discussion. Stockett, Lewis, A bituminous coal breaker in Montana: Min. World, vol. 20, March 26, 1904. Gives section and analysis of the coal bed mined at Stockett, Mont., and a detailed description of the coal breaker use^l by the company. Upham, Warren, Outer glacial drift: Am. Geologist, vol. 34, pp. 151-160. 1904. Discusses the glacial drift of the northwestern States, including Montana. Ref- erence is made to the effect which the glaciation had on the course of Missouri River. Parker, E. W., Mineral Resources U. S. for 1904: U. S. Geol. Survey, pp. 512-515. 1905. Includes a discussion of the various Montana coal fields, their geologic age and im- portance. The production by counties is given, and the State output tabulated from 1880, the year of first reported production. Savage, H. N., Fourth Ann. Rept. U. S. Reclamation Service, pp. 222-224. 1905. Includes report of surveys and lands to be irrigated by the Sun River project. Pirsson, L. V., Petrographic province of central Montana: Am. Jour. Sci., 4th ser., vol. 20, pp. 35-49. 1905. Treats of the various igneous occurrences in the region of Belt and Highwood moun- tains, including a description of the porphyry of the Wolf Butte and Square Butte (of Highwood Mountains) laccoliths, and dike near the Highwoods on Williams Creek. Rowe, J. P., Montana gypsum deposits: Am. Geologist, vol. 35, pp. 104-113. 1905. The gypsum deposits are classified by localities, as the north, middle, and south fields. The middle field includes Cascade and Fergus counties. Includes descrip- tion of Stucco mill on Belt Creek, giving location and age of deposits. Rowe, J. P., The Montana coal fields: Min. Mag., vol. 11, pp. 241-250. 1905. Discusses the production and value of coal from various fields in Montana, including the Great Falls coal field. Treats of present and future development of Belt and Sand Coulee mining districts, including geologic distribution of Montana coals by counties. Boiler tests and chemical analysis of Belt coal are also given. Parker, E. W., Mineral Resources U. S. for 1905: U. S. Geol. Survey, pp. 631-633. 1906. Statistics are given of the Montana coal output, also a short discussion of the different fields. Walsh, William, Report of the Montana inspector of mines, pp. 29-38. 1906. Includes reports of Cascade County mines, their development, production, etc. Calhoun, F. H. H., The Montana lobe of the Keewatin ice sheet: Prof. Paper U. S. Geol. Survey No. 50, 1906. Describes briefly the surface features and geology along the terminal moraine of the Keewatin ice sheet in Montana. Contains detailed description of the glacial deposits and discusses the effects of glaciation of the region on the course of Missouri River. Rowe, J. P., Montana coal and lignite deposits: Bull. Montana Univ. No. 37 (geol. ser. No. 2). 1906. Describes Montana coals by counties. Contains a bibliography of literature bearing on the subject. Fisher, C. A., Great Falls coal field: Bull. U. S. Geol. Survey No. 316. 1907. Describes briefly the coals of the Great Falls region, giving their location, topo- graphic relation, and geologic occurrence. Detailed description of the deposit is given and representative sections introduced. The present development of the vari- ous basins within the field is treated, and the quality of the coal is briefly described, including a number of ultimate analyses of representative coals in the field. Fisher, C. A., Southern extension of the Kootenai and Montana coal-bearing for- mations in northern Montana: Econ. Geol. , vol. 3, pp. 77-99. 1908. 14 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. Describes the Kootenai formation in the vicinity of Great Falls, Mont., tracing it southward across the Montana- Wyoming State line into the Bighorn basin, where it is correlated with the Cloverly formation. The subdivisions of the Montana group in northern Montana, as first worked out by Stanton and Hatcher, are also traced south- ward to the State line. The occurrence of coal in these formations at different locali- ties throughout the area treated is given. Fisher, C. A., Geology and water resources of the Great Falls region, Montana: Water Supply Paper No. 221, U. S. Geol. Survey, 1908. A brief treatment of the general geology of the region is given, with special reference to the prospects for the occurrence of underground water. The surface waters are also described, including their present and proposed uses for irrigation, waterpower, etc. TOPOGRAPHY. RELIEF. The area treated in this report presents a considerable variety of geographic features, all of which have a direct or indirect bearing on the development of the coal resources of the Great Falls field. The area lies within a zone which is transitional between plains and mountain topography, including portions that present features characteristic of both provinces. Its salient features are broad, gently sloping plateaus bordering the adjacent mountain ranges. These plateaus are traversed by numerous mountain streams, which flow through valleys that are deep and relatively narrow in the central portion of the district, but that become wide and open on the plains to both the east and the west. Along the southern margin of the area, from Smith River to the eastern end of the field, the sur- face of the plains rises gradually by sloping plateaus, culminating in a zone of high, hilly country bordering the Little Belt Mountains, which lie to the southward. East of Belt Creek and north of the area described the Highwood Mountains, a cluster of isolated peaks, rise abruptly above the plains to an altitude of 6,700 feet. Between the Highwood and Little Belt mountains there is a divide locally known as the Otter Creek divide, whose altitude at its lowest point is about 4,500 feet. The country east of this divide is drained by Arrow Creek and its tributaries; that to the west by Belt Creek and its largest affluent, Otter Creek, from which the divide derives its name. The range of altitude within the field is moderate. The highest points occur along the base of the Little Belt Mountains, where the more prominent summits rise to an altitude of about 5,500 feet, while the lowest portion of the field lies along Missouri River, below Big Falls, where the altitude is about 3,000 feet above sea level. The average altitude of the region is between 3,500 and 4,000 feet, and the extreme variation in altitude for any given localit}^ is about 1,300 feet in a horizontal distance of 1^ miles. This difference in elevation occurs between Belt Creek and the summit of Belt Butte. TOPOGRAPHY. 15 In the plains province the relative altitudes of the valley bottoms and the summits of the bordering plateaus range from 300 to 600 feet. East of the low divide between the Highwood and Little Belt mountains the country slopes gradually northeastward toward Missouri River. It is traversed by several streams draining the north- eastern slope of Little Belt Mountains. These streams flow through relatively wide open valleys bordered by gravel-capped terraces of different elevation. Stanford Butte, a prominent ridge between Running Wolf and Surprise creeks, is capped by a remnant of an ancient terrace, and to the north and east of this ridge gravel-capped plateaus at lower levels occupy all the interstream spaces. Toward the Little Belt Mountains the gravel-capped terraces give way to prominent hogback ridges formed by the sandstone members of the Ellis and Kootenai formations, which extend in an irregular line along the base of the mountains. Skull Butte, a low dome-shaped uplift about 6 miles south of Stanford, rises nearly 200 feet above the surrounding region. It is considerably dissected about the periphery and in the center by numerous small streams, some of which expose the coal bed of the Kootenai formation, which encircles this uplift. South of Skull Butte there are a number of prominent ridges with long gradual slopes to the north and bold escarpments to the south, overlooking valleys which have been excavated in the softer shale of the Quadrant formation. Throughout the area east of the low divide connecting the High- wood and Little Belt mountains the valleys leading into the moun- tains are wide and open on the plains, but toward the foothill zone they decrease in width, deepen, and branch into many canyon tributaries which cut the upturned edges of the coal-bearing Kootenai rocks, thus exposing the coal bed at many places. These numerous small valleys lead from the zone of coal outcrop in the higher hogback ridges down to the more nearly level plains region where the main line of the Billings and Northern Railroad has been constructed, and thus afford an easy approach to the coal. Broadly viewed, the country between Otter Creek divide and Missouri River, which includes the largest area in the Great Falls coal field underlain by workable coal, is a high plateau sloping gently northward, and deeply dissected by numerous canyons. Otter, Belt, and Boxelder creeks, Sand Coulee, and Smith River are the principal streams traversing this area. All of these except Boxelder Creek flow through deep, narrow valleys which cut through and expose the coal, and along them, owing to the general accessibility of the beds, the principal development of the coal resources of the Sand Coulee area has taken place. The altitude of the plateau varies from 3,500 feet along Missouri River to 4,500 feet or more 16 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. along the southern border of the area. The difference in altitude between valley bottom and plateau summit in the northern part of the district is 200 to 400 feet, but toward the mountains this difference increases to over 600 feet. The streams of this district all flow in a northerly direction except three of the larger tributaries of Smith River — Boston, Ming, and Goodwin coulees — which flow nearly west. Sand Coulee, which is formed by the confluence of a number of canyon tributaries 6 miles southeast of Stockett, continues north- ward for several miles to a point when it turns sharply to the west, and for the remainder of its course it meanders through a wide, flat-bottomed valley formed by the preglacial erosion of Missouri River. West of the Missouri and south of Sun River the surface rises in successive plateaus to the west. The lowest of these, which lies north of Ulm station and comprises what is locally known as Ulm Bench, has an altitude of about 3,650 feet. On the west side of Ulm Bench there is a low saddle separating it from a higher plateau, only a small portion of which is included within the area described. North of Sun and Missouri rivers there is a high plateau region which farther west is deeply dissected by the valley of Muddy Creek. East of Muddy Creek only the southern edge of this plateau is included within the held. It extends eastward as a line of prominent bluffs north of Great Falls, terminating in a group of ridges and buttes of which Black Butte is a conspicuous outlier. DRAINAGE. The Great Falls held, being located along the base of the Rocky Mountain front range, is traversed, especially in its western half, by a number of relatively large mountain streams, some of which have been important factors in the industrial development of the district. The eastern half of the area contains no large rivers, but is drained, as previously stated, by numerous small mountain streams which how northeastward, entering the Missouri by way of Judith River. MISSOURI RIVER. The principal stream of the district is Missouri River. It enters the held near Cascade, and hows in a northerly direction to the vicinity of Great Falls, where it pursues a more easterly course, con- tinuing thus to the border of the held. The portion of the stream above Great Falls hows in a meandering course through a wide, open valley, but that below this point occupies a narrow valley bordered by precipitous bluffs, passing over a number of cataracts known as the Great Falls of Missouri River. At present only one of these falls, Black Eagle, the uppermost of the series, is utilized for the develop- ment of power. The drainage area of the Missouri at Cascade, Mont., TOPOGRAPHY. 17 is estimated as 18,295 square miles, and the flow of the river ranges from 2,000 to 22,000 second-feet. Its largest tributaries from the south are Smith River and Belt Creek, and from the west Sun River. A number of medium and large-sized intermittent streams with relatively large drainage areas enter the river from either side. Bird Creek, Castner Coulee, Sand Coulee and its tributaries, Boxelder Creek, and Red Coulee enter from the south, and Little Muddy Creek enters from the west. The city of Great Falls and the Boston and Montana smelters are located on Missouri River, and the Great Northern Railway has been built up its valley through the Big Belt Mountains, connecting Great Falls with the large mining centers of Butte and Anaconda. SUN RIVER. Sun River rises high in the Lewis Range and joins the Missouri at Great Falls. Only the lower course of the river, however, is included within this field. The main stream is formed by the union of the north and south forks of Sun River, which occurs about 3 miles below Augusta, a town located a few miles east of the base of the Lewis Range, beyond the limits of the field. The principal tributary of Sun River from the north within the area described is Muddy Creek, which drains the high plateau between Sun and Teton rivers, emptying into the latter near Vaughn. It is an intermittent stream of minor importance. SMITH RIVER. Smith River has its source far to the southeast, in the vicinity of Castle Mountains, and flows northwest, draining the highland between the Big and Little Belt mountains. It enters the area described near the center of the south line of T. 17 X., R. 3 E., and, flowing in a northeasterly direction, joins Missouri River at a point near Ulm. Within the district the stream flows in a meandering course through a deep and moderately narrow valley, which exposes high in its bluffs on either side the workable coal bed of the Kootenai formation throughout Tps. 17 N., Rs. 2 and 3 E. Smith River has a flow ranging from about 50 to over 400 second-feet; its largest tributary is Hound Creek, which joins it from the west near Orr post-office. The valley of Hound Creek also exposes the workable coal of the lower part of the Kootenai for about 1 mile above its mouth, and the largest mine in the Smith River district is located on this tributary, in the SW. \ sec. 24, T. 17 N., R. 2 E. Hound Creek, a vigorous mountain stream having a continuous flow, drains the northern end of the Big Belt Mountains, some of its tributaries extending far up the slopes of that range. From the east three intermittent streams enter Smith River — Boston, Ming, and Goodwin coulees. In the upper part of Ming Coulee, in the vicinity of Eden, the valley exposes the coal 54937 — Bull. 356—09 2 18 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. measures, and here a number of small mines have been opened. The same is true in the upper part of Boston Coulee. Smith River Valley and its principal tributaries, Ming and Boston coulees and Hound Creek, furnish a valuable means of' access to the coals of this little-developed portion of the Great Falls coal field. The large flow of water in Smith River is also an important consideration in the development of this coal district, for the percentage of impurities present in the coal is sufficient to render washing necessary before it can be successfully placed on the market. In neither Boston nor in Ming coulee is there sufficient water to wash the coals that could be mined from them, but the impurities might be removed by a dry- washer process such as is now employed at Stockett. BELT CREEK. Belt Creek rises in the northern part of the Little Belt Mountains, flows northward across the central part of the district, draining the territory west of the Highwood Mountains, and enters the Missouri about 12 miles northeast of Great Falls. It flows through a valley about 300 feet deep, which has a width varying from one-half to three-fourths of a mile. In the vicinity of the town of Belt, where the valley crosses the area underlain by coal, it exposes in the bluffs on either side, a short distance above the valley, beds of coal of workable thickness, thus producing favorable conditions for the development of the deposits. A number of mines are located there, including the Anaconda Copper Mining Company’s mine, one of the largest in the Great Falls coal field. Belt Creek is a vigorous mountain stream which carries a large flow of water throughout all seasons of the year, especially in its upper course, but at the town of Belt all this water sinks to an under- flow during the late summer months, leaving the stream bed dry. This loss is due principally to the fact that the valley floor here consists of soft, porous sandstones, into which the water passes readily. From a point a short distance below the town of Belt to its mouth the stream has a small but continuous flow. A view of the dry bed at Belt is shown in PI. III. The sinking of the flow of Belt Creek at Belt is a disadvantageous feature from a coal-mining point of view, for it renders it necessary to sink wells in the valley in order to obtain a sufficient amount of water to wash the impurities from the coal. The principal tributaries of Belt Creek are Otter Creek from the east and Neel Creek from the west. Otter Creek rises on the northern slope of Little Belt Mountains, and, flowing northwest, enters Belt Creek about 1 mile above Armington. It carries considerable water derived from snow on the mountains and from springs along its course. Neel Creek is a much smaller stream, having an inter- mittent flow. In the lower part of the valley of Neel Creek coal of BULLETIN NO. 356 DRY BED OF BELT CREEK, NEAR BELT, MONT. TOPOGRAPHY. 19 workable thickness is exposed. That part of Otter Creek Valley which lies between Spion Kop and Nollar’s mine crosses an area underlain by valuable coal deposits, but in the center of this area the valley is not cut sufficiently deep to expose the coal, which, however, could be easily reached by shafting. The favorable location of this valley with respect to the limits of the coal area offers a valuable means of access to the deposits. OTHER SMALL STREAMS. The area between Belt Creek and Smith River is drained by Boxelder Creek and Sand Coulee. Boxelder Creek rises high on the plateaus about 3 miles west of Riceville, flows northward in a direction roughly parallel to Belt Creek, and enters the Missouri about 9 miles east of Great Falls. It carries only a small flow of water, and its valley in the upper part, where coal-bearing rocks occur, is not cut sufficiently deep to expose the coal; hence it is not an important factor in the development of this part of the Great Falls coal field. Sand Coulee, an intermittent stream with a large drainage area, is formed by the union of several small canyon tribu- taries southeast of Stockett. It continues northward to a point about 6 miles below Stockett, where it makes a sharp turn to the west and meanders through a wide, level-floored valley for about 7 miles, entering Missouri River about 4 miles above Great Falls. This O intermittent drainageway, especially in its upper course, and its tributaries from the west, Straight and Giffen coulees, have deep narrow valleys, which cut and expose the coal-bearing zone of the Kootenai formation, thus producing favorable conditions for develop- ment. It is in the valleys of these intermittent streams, where the towns of Stockett and Sand Coulee are located, that the greatest coal mining activity has taken place. East of Otter Creek there is a prominent ridge that forms a low divide between Highwood and Little Belt Mountains. The drainage to the east of this divide, as previously stated, is all to the northeast, into Arrow Creek, a small tributary of the Missouri entering the latter a short distance above the mouth of Judith River. Arrow Creek, which has its source on the southern slope of Highwood Mountains, flows eastward, passing out of this district in T. 18 N., R. 11 E. Its principal affluents are Surprise and Running Wolf creeks, the former having its source at the base of Wolf Butte and pursuing a north- easterly course. Running Wolf Creek rises higher up the slopes of the Little Belt Mountains farther to the southeast, and flows north- eastward past Stanford Butte. East of Running Wolf Creek several small branches cross the extreme southeast corner of the district and enter Judith River. These are Skull, Willow, and Sage creeks, all of which, as previously stated, expose in their upper courses work- able beds of coal. 20 GEOLOGY OF GllEAT FALLS GOAL FIELD, MOMAtfA. CULTURE, Settlement in the Great Falls field, as elsewhere* is determined by geologic and climatic Conditions, Along all the larger stream valleys where surface water for irrigation purposes is available settlements are numerous, while much of the upland and grazing districts is thinly populated. On the higher slopes bordering the mountains in the zone of increased rainfall there are many small farms, some of which are among the best improved places in the district. There is one relatively large town, three medium-sized coal-mining towns, and a number of smaller trading points. Great Falls, a town of 18,000 inhabitants and a thriving business center, is located on Missouri River near the north-central portion of the field. While at present none of its railroad lines are transcontinental, they are the most important connecting lines between the Great Northern and the Northern Pacific, and when the Billings and Northern is completed it will open up a new transcontinental route through Great Falls to the northwest coast. At the present time railroads extend in four directions from Great Falls“one southwest to Helena and Butte; another northwest to Havre, a small town on the main line of the Great Northern; a third, the Montana and Great Northern, north- west to Shelby Junction; and a fourth, the Neihart branch of the same road, southeast to Neihart. The last named is connected with Stockett and Sand Coulee, two of the larger coal-mining camps, by a short branch line from Gerber station. The Boston and Montana Consolidated Copper and Silver Mining Company’s smelters and refineries are located at Great Falls, as is also the Royal Milling Company’s plant and a number of smaller business enterprises. The ore handled at the smelters comes from Butte and Anaconda; this, together with the coal and limestone used in the operation of the plant makes a relatively large freight traffic for Great Falls, while it also fur- nishes employment for a large number of men. Belt, one of the largest coal mining towns in the district, has a population of about 1,000, composed mainly of employees of the Anaconda Copper Mining Company, the largest coal-mine operator at the place. It is located on Belt Creek, about 25 miles southeast of Great Falls, on the Neihart branch of the Great Northern Railway, and is the oldest coaling town in this region. About 10 miles south- west of Belt and nearly 20 miles from Great Falls are the two coal- mining towns of Stockett and Sand Coulee. Stockett, which has a population of about 800, composed largely of coal miners employed by the Cottonwood Coal Company, one of the two largest coal min- ing companies operating in the district, is located on East Fork of Sand Coulee. Sand Coulee, about 2 \ miles northwest of Stockett, is a smaller mining town of about 400 people. It is situated in Cotton- wood Coulee, a branch of Sand Coulee, and owes.its existence mainly U. 8. GEOLOGICAL SURVEY BULLETIN NO. 350 PL. IV COLUMNAR SECTIONS OF THE STRATIGRAPHY ALONG BELT CREEK VALLEY. (Columns are numbered from left to right.) 1, West side of Belt Creek, 1 mile north of Goodman siding; 2, east side of Belt Creek, 2£ miles north of laoodman stding; 3, west side of Belt Creek, one-eighth mile above mouth of Otter Creek; 4, east side of Belt Creek, one-eighth mile below mouth of Otter Creek; 5, east side of Belt Creek, one-half mile above Belt; 6, east side of Belt Creek at Belt; 7, west side of Belt Creek at Belt. V! ■ vr'jjuc: v. ■ ■ } : . - - ■ . u STRATIGRAPHY. 21 to the Nelson and Gerber coal companies, which are operating at this place. The remainder of the towns within the district are supported mainly by a ranch population. There are no towns along Missouri River below Great Falls within the area described, but above that town there are two small stations, Ulm and Cascade. The latter, located near the base of the Big Belt Mountains, has a population of about 200, and is supported by a large ranch trade along either side of the river. About 2 miles above the mouth of Smith River there is a post-office known as Truly, and farther up the river there was another known as Orr, which has recently been discontinued. In Belt Creek Valley, about 2 miles above Belt, is the small town of Armington, which is situated at the junction of the Billings and Northern Railroad and the Neihart branch of the Great Northern. It is mainly a small railroad town, which receives a portion of the ranch trade of the surrounding country. Along the Billings and Northern Railroad there are a number of new towns and sidings? located at intervals of about 6 miles. These are Reinsford, Spion Kop, Geyser, Stanford, and Windham. Old Stanford and Old Geyser? which are located at some little distance from the new town sites bearing these names, are important trading points for a large ranch district along Arrow, Skull, Running Wolf, and Sage Creek valleys. DESCRIPTIVE GEOLOGY. STRATIGRAPHY. GENERAL OUTLINE . The surface formations throughout the area to which this report relates consist mainly of sedimentary rocks and igneous intrusives in the form of dikes and laccoliths, the intrusives being especially abun- dant throughout that part of the field bordering the adjacent mountain ranges. The strata lie in general nearly horizontal, dipping at a relatively small angle to the north and east, away from the mountains and toward the plains. Throughout most of the Great Falls field the rocks lie apparently flat, but on closer examination they are found to be gently folded into a series of shallow synclines and low anticlines. These, however, are scarcely perceptible to the casual observer, being revealed only by careful examination of the beds exposed along the sides of some of the valleys. The rocks are representative of Car- boniferous, Jurassic, Cretaceous, Tertiary, and Quaternary systems. The distribution of the formations is shown on the geologic map (PI. I), and their stratigraphy and structural relations are illustrated in the columnar and cross sections shown on PL IV and PI. VII. The table on pages 22-23 shows the age, order, characteristic features, thickness, distribution, stratigraphic relations, and economic impor- tance of the formations. 22 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. ' ’2 b g K a m m P P *5 =3 S-° o oSgg CO .2 g © ® © g •0,0 P 0.2 - 0 j£ o o Sp p © o £ So c > g M 09 ° 0.2 .9® ?? or <73 03 ^ o* &0*M o g II ||i| S§?go g P o — © P rj ot P r. oST^P ®P oa P ®^2'P £•- «§ © 3 &Q P-O o © § S +s £*© 6 gp 0,0 p > ^“ © pp o be W o o £.2 s “p : P^|l at -.2 c3 W — 1 CO ,0 ! 3 M ■5-d 2 05 p.9 — © «s >> JS «* °,g«= rO ^ _ +* g -P ^ a; ^ op gsl’go^o 5 9 ^ ^ P4C3 CO o CO n So a © og ^ o p 2 0 9 g<.2 p •*> P P O £_i Si ^ c _© o ■ 00 to £ 3 © OT © o be >5 s-gsas +3 O®* >* o3,C © g ®<4- P 2 Jp O oj ft O OO . © p ^2 £S-c &= = I 6 ! 53 p o 8£l3 9 p O Sh © o >>Sb sgl 5*1 Q /2 U gfei O & !b ©OO 0 Cs «.p ft£ c OT ©^ o ft © o3ft P.g ft O ,.9 !> © ^ -'a | 3>S © 03 P ©— 1 p o ,2 £.g §°oS* be © 03 .2 g .S^^O >-< © © ^_, <*H ~0 © O o © fcOp h r © o .p S^BQ 0.2 fgp£| o o es 03 p • 3 ^ gg ro o*--« ^ ©w^ IfO Se© c3 O © ~ -! 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P © © °3 P o3P mP •^Ip 5-8 § .2 £ © S®g in © 1 ' tc © ►> pp u te-P o o © • 5S§.9 ^ r. o3 P o3 g o3 P 9 -2 w g © §„ ■S p2 9 © o -|+»0 •9 S.9 SfbC C3P O — C o .2 ^ - c § 1st pi ■sSsggg QOm © ° 9 ftop o<© — I'Sg^pa si g £ p^: o3 ftbC© c3 O © © — P O P — u .SOT S g ^ 0 § 2 ©P m 5pn © - P^-O >,® g ; S 03 O © -jrS § § o © be ©.2 P o ©o II S^- 2 -SSftSi -Sofe^ 53 .9 ® Sl3 <»g 9 £ p 8 03p . © (-P I § 03 ® ftp- o.P .tOc 'S "C ^ -i a o^r,^ ftft © OT +J Q( c3 >> fl 3 cy STRATIGRAPHY. 23 IS 8 ispiiii § S § A “ .ft|c|| ^•2 = §“S*feSS |pjisg.sl».s 13l.sS2£g§lf 1111 °Jl3 Iff sills am HU! A5 8 yitii .2^°° & “i:p ff iiSsSg Jj.SSja'i’S’a 80 to 120. 80 to 120. § 2 1 140 exposed. Variegated shale and clay, containing sandstone lay- ers, one above the middle of the formation; cinna- mon-brown color; bone- bearing; limestone layers sometimes present i n lower part. Dove - colored limestone, overlain by reddish-brown, coarse-grained sands tope, coarsely conglomeratic at base. Sandstone, red and green shales, clays, and lime- stone, with an occasional bed of gypsum in lower part; also one at the top. 1 Massive, light -grav lime- stone and argillaceous shale. Hcc o-^ ■So|0 | = g| >11 ;I fsW sS|!l f*ii “«1S2 24 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. SEDIMENTARY ROCKS. CARBONIFEROUS SYSTEM. MADISON LIMESTONE. General statement.— The Madison limestone is very conspicuous along the north side of the Little Belt Mountains, but the greater part of it lies outside of the area here described. The only exposures in the district are along East Fork of Sand Coulee and its tributaries and on Smith River, where a local' doming of the beds exposes 100 to 200 feet of the formation. Its distribution is shown on the geologic map (PL I). Along the flanks of the Little Belt Mountains outside of the area to which this report relates the limestone has a thickness of about 1,000 feet and consists of three members. The lowest member, which is more or less argillaceous, has been called the Paine shale, the more massive limestone of the middle part the Woodhurst limestone, and the top member the “ Castle” limestone. In the Little Belt Mountains the Madison limestone carries a typical Mississippian fauna. “ Castle ” limestone member . — The “Castle” limestone member, which forms “Sluicebox Canyon,” the lower end of which is at Riceville (PL V), is exposed to view at numerous places in the vicinity of Stockett; farther south, in the head of Ming Coulee; and on Smith River. Within the area examined its greatest observed thickness is about 140 feet, which is found at the head of Ming Coulee, about 10 miles southwest of Stockett. Here the rock is massive, compact, and of a medium-gray color, but weathers light. It occurs in strata 15 to 20 feet thick, which at many places have weathered to rough, cavernous surfaces, forming castellated masses. Interbedded with the massive strata are thin layers of softer calcareous material. At Stockett 15 feet of oolitic limestone was observed in this formation, underlain by compact light-colored limestone. The fossils listed below were collected from © the limestone at Stockett and at the head of Ming Coulee, outside of the area described: Fossils from Stockelt, Mont. Spiriferina solidirostris. Seminula madisonensis. Seminula liumilis. Cleiothyridina crassicardinalis. Eumetria verneuiliana. Fossils from head of Ming Coulee. Schuchertella sp. Eumetria verneuiliana. Spiriferina solidirostris. Camarotoechia sp. Seminula madisonensis. Amplexus sp. Zaphrentis sp. Syringopora surcularia. Schucliertella sp. Spirifer centronatus var. GEOLOGICAL SURVEY MADISON LIMESTONE OVERLAIN BV QUADRANT SHALE, NEAR RICEVILLE, MONT, STRATIGRAPHY. 25 These fossils were determined by George H. Girty, who regards them as Mississippian in age. The Madison limestone in the vicinity of Riceville is overlain by the brick-red sandy shale or impure sandstone of the Quadrant formation, but farther west, in Sand Coulee and its tributaries, and also at the head of Ming Coulee and on Smith River, the Quadrant is absent, the basal limestone or the calcareous conglomeratic sand- stone of the Ellis formation resting upon the Madison limestone. These unconformable relations are shown in cross section C-C, PL I, and on PL VI. QUADRANT FORMATION. Character and extent . — The Quadrant formation comprises a suc- cession of beds of variable character and thickness which immediately overlie the Madison limestone in most places throughout the Little Belt Mountains region. These beds, although different in character, have been regarded by Weed as the stratigraphic equivalent of the Quadrant formation near Quadrant Mountain in the Yellowstone Park region, where the name was first applied. The Quadrant for- mation in the Great Falls field consists of sandy shale or argillaceous sandstone and limestone with beds of gypsum in the lower part and near the top. It is not coal bearing, and consequently is not included in the area studied except at a few localities, notably on Belt Creek near Riceville, on Little Otter Creek 2J miles above its mouth, along the base of Little Belt Mountains from Geyser Creek to near the southeast corner of the area described, and in the central part of Skull Butte. No careful study was made of the stratigraphy of the formation except on Belt Creek near Riceville, where the basal mem- ber consists mainly of red and green sandy shale with an occasional bed of white gypsum and a few thin layers of white limestone. Very few typical sandstone members were observed at this locality, although Weed a has applied the name Kibbey sandstone to the basal member of the Quadrant in this general region. The upper member of the section, which the same writer has designated the Otter shale, consists largely of red and green sandy shale with limestone layers occurring at frequent intervals. No gypsum was observed in this part of the section except near the top. The following section of a part of the formation was measured near Riceville: Section of part of Quadrant formation on east side of Belt Creek near Riceville , Mont. Ft. in. Shale, dark green. . j. 51 Limestone, white 1 Shale, green, sandy 1 a Weed, W. H., Description of the Fort Benton district: Geologic Altas U. S., folio 55, U. S. Geol. Survey, 1899. 26 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. Section of part of Quadrant formation on east side of Belt Creek near Riceville , Continued. Ft. Limestone, white, compact, laminated 2 Shale, dark greenish 20 Shale, greenish, sandy 20 Limestone, dove-colored, thinly laminated 1 Shale, red and green, containing hard limestone layers 68 inches thick 25 Limestone, alternating layers of, and shale, greenish 7 Shale, red, containing layers of dove-colored limestone in lower part 14 Limestone, blue, compact, porous 3 Limestone and shale, gray, alternating layers of white and dove- colored limestone thinly laminated, with an occasional bed of ' gray shale 20 Soft sandy material 11 Limestone, hard, gray, compact 3 Shale, dark green, sandy 20 Limestone, hard, gray, compact 1 Soft sandy material 8 Gypsum, white 3 Gypsum, impure, and dark-gray shale, with nodules of black flint 6 Shale, greenish, sandy, containing thin layers of white limestone. . 34 Limestone, white.. Shale, green, sandy , 6 Limestone, white Shale, green, sandy 29 Limestone, white, compact 2 Gypsum, white 2 Shales, red and green, sandy .* 34 Beds concealed 7 Shale, red 17 Madison limestone. Mont .- — in. 6 6 6 6 6 6 8 6 Total 352 2 The total thickness of the formation as observed near Riceville is less than 500 feet, but according to Weed® its thickness greatly increases toward the southeast, reaching a total of 1,400 feet near Utica. Farther east, along the Little Belt and Big Snowy mountains, W. R. Calvert 6 has observed that the Quadrant has a thickness vary- ing from 450 to 750 feet, while its lithologic character is not materially different from that shown on Belt Creek, except for the absence of beds of gypsum. The Quadrant formation is overlain unconformably by the basal limestone and conglomeratic sandstone of the Ellis formation, and rests with apparent conformity on the underlying Madison. There is, however, a very abrupt change in the character of the rocks at a Weed, W. H., Twentieth Ann. Rept. U. S. Geol. Survey, pt. 3, 1898-99, p. 295. b Calvert, W. R., Geology of the Lewistown coal field, with special reference to coal: Bull. U. S* Geol. Survey (in preparation). STRATIGRAPHY. 27 the Quadrant-Madison contact, probably indicating a hiatus. The details of distribution of this formation are shown in PI. I. ^^_p re vious workers in this field have published statements concerning the age of the Quadrant which are somewhat at variance, having assigned the formation to both the “ Lower” and “ Upper ’’ Car- boniferous. While, as previously stated, no special study was made of the Quadrant formation during the investigation of the Great Falls coal field, subsequent observation has thrown some light on the age of these beds. Along the north side of the Little Belt Mountains, in the vicinity of Utica, a few miles beyond the eastern border of the Great Falls coal field, W. R. Calvert and the writer obtained a large collection of fossils from the Quadrant, and Calvert made additional collections from this formation farther east in the Judith basin. a These collections have all been studied by George H. Girty, who makes the following statements concerning their age : The several collections made in the Quadrant in this area indicate a single uniform fauna. A definite opinion as to the age of the Quadrant fauna must be reserved until more complete evidence has been obtained and more extensive investigations have been undertaken, for the facies is very largely new to the American Carboniferous. At present it seem probable that the Quadrant will prove to be of early Pennsylvanian or Pottsville age. Faunas which have an upper Mississippian facies and are younger than the Madison have been cited from the Little Belt Mountains and referred to the Quadrant. They are considerably different from the Quadrant fauna of this report, and it seems possible that three distinct faunas will be involved in the problem — a Madison fauna, a late Mississippian fauna, and a post-Mississippian fauna. The fauna of the typical Quadrant is at present unknown. JURASSIC SYSTEM. ELLIS FORMATION. Character and extent . — The Ellis formation includes a basal lime- stone of variable thickness, ranging from 15 to 60 feet, which in places merges upward into a coarse conglomerate that passes into a medium- grained sandstone, light brown to gray in color, and more or less thin bedded. In other localities, however, the change from limestone to conglomerate is abrupt. The limestone and conglomerate contain marine Jurassic invertebrate fossils. Some of those in the conglomer- ate are fragmentary, but more are complete, with pebbles of lime- stone and quartzite several inches in diameter. The component parts of the conglomerate are bound together by a calcareous cement. The total thickness of the formation is about 80 to 120 feet. It rests unconformably upon the shale of the Quadrant formation in certain parts of the field, and upon the Madison limestone in others. (PI. VI. ) The exposed area of the Ellis formation is not large throughout the Great Falls region. It is exhibited in the sides of the bluffs bordering Smith River and its tributary, Hound Creek, also along Sand Coulee a Op. Cit. 28 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. and its various branches in the vicinity of Stockett, and along Belt Creek from Armington to the southern border of the district. East of Belt Creek the formation is exposed in the head of Otter Creek and its numerous branches from the south ; also throughout a zone of varying width extending to the southeast along the northern slope of the Little Belt Mountains. Skull Butte is encircled by a narrow band of the formation. The details of distribution of the Ellis formation are shown on the geologic map (PI. I). The following sections illustrate the succession of the beds of the formation in different parts of the field : Section of Ellis formation near Goodman siding , Montana. Feet. Sandstone, massive, light brown to gray, weathering tan, conglomer- atic and fossiliferous at base 66 Limestone, reddish brown, fossiliferous 6 Beds concealed (estimated) 18 90 Section of Ellis formation at head of Ming Coulee , Montana. Feet. Sandstone, gray, weathering brown, thin bedded 60 Sandstone, gray, conglomeratic, containing marine Jurassic fossils . . 29 Limestone, dove colored, massive; basal member brecciated and containing Jurassic fossils 60 149 Fossils. — Fossil invertebrates, mainly Ostrea and Camptonectes , are present in great abundance in the two lower members of the above section. The numerous specimens of these genera and a few other forms are sufficient to determine that the rocks belong to the Ellis for- mation, which in the Yellowstone National Park and neighboring areas yields a characteristic upper Jurassic fauna. The sandstone of the Ellis formation throughout the Great Falls region is usually not fossiliferous, but the conglomerate and underlying limestone contain an abundance of Jurassic fossils. Near the head of Hazlett Creek, in sec. 31, T. 16 N., R. 11 E., forms were collected from thin layers of limestone near the base of the Ellis formation, and were identified by T. W. Stanton as Rliynchonella myrina Meek?, Ostrea strigilecula White, Camptonectes sp., and Belemnites sp. From the conglomerate sandstone of the Ellis formation on the east side of Otter Creek a small collection of fossils was made, from which T. W. Stanton recognized a smooth, simple form of Ostrea , very abun- dant; Ostrea ( Alectryonia ) sp.; and Eumicrotis curta Hall?. MORRISON SHALE (?). Character and extent. — The Morrison formation, which is extensively exposed along the Rocky Mountain front range in southern Montana BULLETIN NO. 356 PL. BASAL JURASSIC SANDSTONE LYING UNCONFORMABLY ON MADISON LIMESTONE NEAR STOCKETT, MONT. A is about 1 mile south of B. STRATIGRAPHY. 29 and Wyoming, is also believed to occur along the northern base of the Little Belt Mountains. In previous investigations in this field by Weed and others the Morrison formation has not been recognized, and the beds comprising it have been grouped with the Kootenai and included in the “ Cascade ” formation. During the last field season dino- saur bones provisionally regarded by C. W. Gilmore as of Jurassic age were found at one horizon in many different localities; and at one exposure in sec. 3, T. 16 N., R. 2 E., about 30 feet below the bone- bearing bed, a green shale containing a distinctly fresh- water fauna later than the Ellis formation was seen. These rocks, here provision- ally regarded as constituting the Morrison formation, consist of sand- stone and bright-colored sandy shale with scattered layers of impure -limestone, many of them in lenticular form. The formation lies with apparent conformity on the Ellis and is overlain conformably by the Kootenai. The thickness ranges from 60 to 120 feet, but the exact limits of the formation are in many places difficult to determine. Fragments of bone have been found at different horizons throughout the overlying Kootenai formation, but thus far none that are suffi- ciently well preserved for specific determination have been discovered in this region. It is possible that future investigation may prove that the rocks here tentatively regarded as belonging to the Morrison con- stitute in reality a basal member of the Kootenai. The formation is generally exposed in a narrow band on the inner rim of a low ridge formed by the harder overlying rocks of the Koote- nai formation. It outcrops all along the base of the Little Belt Moun- tains, from the east end of the district to Smith River. Good expo- sures occur along the upper courses of Sage, Skull, Running Wolf, Hazlett, Surprise, Geyser, and Otter creeks and in the bluffs for some distance back from the mountains along Belt Creek, Sand Coulee, Smith River and its principal tributar} r , Ming Coulee. The following sections show the succession of the beds: Section of supposed Morrison formation on the north side of Smith River in the /SIP. \ sec. 29, T. 17 N., R. 3 E., Montana. Kootenai formation. Morrison formation : Feet Shale, soft, sandy 52 •Limestone, light-colored, nodular 4 Shale, variegated 33 Sandstone, gray, massive 11 Shale, greenish gray, sandy 20 Ellis formation. 120 30 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. Section of supposed Morrison formation on the east side of Belt Creek in the NE. \ sec. 30, T. 18 N., R. 7 E., Montana. Kootenai formation. Morrison formation : Feet. Shales, maroon and green 52 Shale, green, capped by \\ feet of sandstone, gray 5 Sandstone, calcareous, weathering light brown 5 Shale, greenish 20 Sandstone, massive, weathering light brown 7 Shale, dark green, containing thin limestone layers 9 Ellis formation. 98 Section of Morrison and part of Kootenai formation in the NE. ^ sec. 3, T. 16 N., R. 10 E., near Shannon Creek , Montana. Kootenai formation : Ft. in. Sandstone, gray, massive 60 Coal (estimated) 6 Beds concealed 60 Morrison formation : Beds, concealed 22 Shales, red and green, containing ironstone layers at base 46 Limestone, light colored, fossiliferous 5 Shale, green, sandy, fossiliferous 25 Limestone, white, fine-grained, thin bedded 6 Shale, green, sandy ' 13 ■ 237 6 Fossils . — Invertebrate fossils collected from a locality where Shannon Creek was measured have been examined by T. W. Stanton, who reports three species of Unio, apparently all undescribed; Neritina sp. and Valvata cf. scabrida M. and H. Mr. Stanton’s comments on this collection are as follows : This is a fresh-water fauna later than the Ellis and suggestive of the Morrison, although there are no identical species, with the possible exception of the Valvata. From the red and green shales about 1 mile west of the above- described locality were collected saurian bones which C. W. Gilmore describes as “a portion of the centrum of a large vertebra, which, from its size, might well represent one of the large herbivorous dinosaurs of the Jurassic (Morrison).” CRETACEOUS SYSTEM. KOOTENAI FORMATION. General statement . — The Kootenai formation, as determined by the present investigation, comprises the upper one-third of the Cascade and Dakota and the basal red shale included in the Colorado shale, as described by Weed a in the Fort Benton folio. The name Cascade, a Weed, W. H., Geologic Atlas U. S., folio 55, U. S. Geol. Survey, 1899, U. S. GEOLOGICAL SURVEY BULLETIN NO. 356 PL. VII Formations. Character of Rocks. Shales, dark, with layers of sandstone. Beds partly concealed; thin-bedded sandstone at base. Beds concealed Sandstone, dark gray, soft Sandstone, dark gray, hard, forming bold ledge Colorado (Upper Cretaceous) Sandstone, gray Shales, dark gray, sandy Shales, greenish, sandy. Shales, red, sandy, only partly exposed Kootenai (Lower Cretaceous) Shales, reddish, sandy, with thin-bedded sandstone. Limestone, light brown, compact, fossiliferous Shale, purplish, with lilac thin-bedded sandstone . . . Shales, light, sandy, capped by sandstone Shales, purplish, with limestone and sandstone Clay, red, capped by sandstone Conglomerate, clay -ball, capped by rust-colored limestone. Shales, greenish to purple, sandy, with limestone lenses .- . Sandstone, gray, massive, shaly at base Shales, dark gray Coal. Shales, greenish, soft, sandy. Morrison (Cretaceous or Jurassic) Sandstone, gray, massive, thin bedded at base Conglomerate, pebbly, lenticular Shales, maroon and greenish, sandy Shales, sandy, and calcareous sandstone .1 Shales, green, sandy I Sandstone, tan-colored, massive [ Shale, dark green, containing layers of limestone ’ Ellis (Jurassic) Sandstone, gray, massive, conglomeratic, fossiliferous Limestone, conglomeratic, fossilifero us Shales, dark green, with beds of clay at top Gypsum Shales, variegated, sandy, alternating with limestone. Quadrant (Pennsylvanian) Madison (Mississippian) Shales, dark, with limestones at base Limestones, white and dove-colored . . . . . . . . . . . . Shale, sand, and hard, brecciated limestone Shale, dark green [ Gypsum, lenticular Shales, green, sandy, with thin white limestone at base Shales, green, sandy, alternating with white limestone. . . Gypsum Shales, red and green, soft, sandy Shale, red, sandy Limestone, white, massive 300 feet COLUMNAR SECTIONS SHOWING STRATIGRAPHY IN DIFFERENT PARTS OF GREAT FALLS REGION, MONTANA. . •' ; . , STRATIGRAPHY. 31 as referred to a Cretaceous formation, was first used by that author in his description of the rocks of the Fort Benton quadrangle, to apply to a series of beds ranging in thickness from 225 to 500 feet. The lower part of the formation, as originally described, consisted of lavender- tinted sandstone containing at its base a workable bed of coal. Dur- ing the present investigation, as previously stated, saurian bones believed by C. W. Gilmore, of the United States National Museum, to be of Jurassic age, were discovered in the lower half of the so-called “ Cascade ” formation, indicating that these beds are probably of Morri- son age, although vertebrate remains occur in the sandstones of the overlying Kootenai. Between a horizon 45 feet below the coal bed and the top of the “ Cascade” formation as above defined fossil plants of Kootenai age were collected at five different horizons, establishing beyond question the Lower Cretaceous age of this portion of the forma- tion. On the east side of Spanish Coulee, a tributary of Smith River, at a horizon about 150 feet above the “ Cascade’ ’ formation, in beds the equivalent of which in the vicinity of Belt have been provisionally regarded by Weed as of Dakota age, a large collection of Kootenai plants was procured from dark-colored shale associated with red and green shales and clay. Overlying this plant-bearing bed is about 200 feet of rocks consisting of red shale and sandstone not differing mate- rially in stratigraphy or lithologic character from beds immediately underlying the plant horizon. The close lithologic resemblance of this upper member to the underhung well-defined Kootenai rocks, together with the apparent absence of Dakota floras in it, has been regarded by the writer as sufficient evidence for provisionally includ- ing the beds in question as of Kootenai or Lower Cretaceous age. These beds are overlain by dark-colored shale and sandstone of the Colorado formation, in the lower part of which were discovered marine saurian remains. In this report it does not seem advisable to employ the name “Cascade” for the following reasons: First, the term has not been so extensively used in the literature as the term Kootenai; second, its usage would necessitate redefining the term, in order to separate its lowest member, which is now believed to be Morrison: third, the beds immediately overlying the “Cascade” formation can not be differen- tiated paleontologically from it, both being of Lower Cretaceous age, rendering it necessary to place the upper limit of the formation in question purely on lithologic grounds. Character and extent . — The Kootenai formation consists of alter- nating layers of sandstone and shale, with the former predominating, especially in the lower half. The sandstones range in thickness from 10 to 60 feet, and are more or less massive in character. In the upper part shales are more abundant and are interbedded with thin layers of impure sandstone. At Belt, on the east side of Belt 32 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. Creek, where a complete section was measured, the basal member of the formation consists of a sandy shale interbedded with sandstone, the latter predominating, the whole having a thickness of about 60 feet. This member consists locally of firm, massive sandstone with only a small percentage of shale. It is overlain by coal, which here has a thickness of 6 feet, including a few thin partings. Above the coal there is a dark, coaly shale 5 to 6 feet thick, covered by 38 feet of massive light-gray sandstone. This sandstone is overlain by 138 feet of beds, consisting in ascending order mainly of alternating layers of sandstone, red shale, and clay, with an occasional limestone lens in the lower part. Above this alternating series there is about 200 feet of red shale, which constitutes the topmost member of the formation. The total thickness is about 450 feet, which may be regarded as representative of the Kootenai formation as exposed along the Belt Creek valley. In previous reports on the geology of this region by Weed a greatly exaggerated thickness (736 feet) was assigned to beds lying between the base of the Ellis and the coal bed of the Kootenai formation. Of this amount the lower 215 feet was regarded as belonging to the Ellis and the remainder to the Kootenai formation, the presence of the Morrison between these two formations not having been recognized. During the present investigation a number of detailed sections measured along Belt Creek proved conclusively that the strati- graphic interval between the base of the Ellis and the Kootenai coal, to which Weed had assigned a thickness of 736 feet, is in reality only about 300 feet. According to the present classification the lower 120 feet of these beds has been assigned to the Ellis; an equal thick- ness immediately overlying, in which fresh-water invertebrates and land animals occur, to the Morrison; and the upper 60 feet, which is plant bearing, to the Kootenai. PL IV, which contains a number of columnar sections measured along Belt Creek valley, illustrates the character and thickness of the various formations. On the north side of Skull Butte the base of the Kootenai consists of a soft light-gray massive sandstone, but in other respects the portion of the formation exposed in this locality agrees closely with the beds exhibited at Belt Butte. A section of the Kootenai on the north side of Skull Butte is given below: Section of a part of Kootenai formation on north side of Skull Butte , Montana. Shale, reddish, sandy. Ft. in. Sandstone, gray, thin bedded 1 6 Shale, reddish, sandy, with layers of sandstone in lower part. . . 21 Sandstone, greenish, gray, weathering dark; thin bedded above, clay-ball conglomerate below 4 Shale, reddish, sandy, with layers of sandstone in lower part ... 27 Sandstone, gray, cross-bedded; clay-ball conglomerate in lower part 5 6 STRATIGRAPHY. 33 Section of a part of Kootenai for motion on north side of Slcull Butte , Montana — Cont’d Ft. in. Shale, reddish, sandy - - 30 Sandstone, soft, thin bedded 20 Sandstone, gray, massive; clay-ball conglomerate 3 6 Shale, red, sandy 38 Sandstone, gray, massive; clay-ball conglomerate 5 Shale, red, sandy 24 Sandstone, calcareous, alternating with sandy shale 20 Sandstone, light and dark gray, massive, fine grained 86 Coal (estimated) 6 Sandstone, gray, massive, soft 62 353 6 The Kootenai has the greatest areal distribution of all the forma- tions outcropping within the area. It caps the surface for a great part of the district lying between Smith River and Belt Creek, and is the surface formation of the high plateaus south of Otter Creek. Beyond Otter Creek it is exposed as a band of varying width which narrows toward the east. Fossils . — The Kootenai formation of the Great Falls district car- ries an abundant fossil flora of Lower Cretaceous age. Fossil plants of Kootenai age were first discovered in the Great F alls coal field in 1889 by J. S. Newberry.® From these fossils, which consisted of only a few species, it was possible to correlate the rocks of the Great Falls region with the Kootenai north of the international boundary line, described by George M. Dawson. In 1890, during the construction of the Great Northern Railway line between Helena and Great Falls, Mont., a larger collection of Kootenai plants was made from a rail- road cut near the flood siding on the Missouri; these were reported on by Newberry in 1891 . b About the same time that the above collection was obtained F. H. Knowlton and A. C. Peale made a small collection of plants from the same railroad cut, and the follow- ing year W. H. Weed also procured plants from this locality which were studied and described by W. M. Fontaine in 1892. c In 1894-95 Kootenai plants were found at a number of localities by W. H. Weed and L. F. Ward, mainly south and east of Geyser. These were de- scribed by W. M. Fontaine in Ward’s second paper on the 11 Status of the Mesozoic floras of the United States.” d During the present investigation fossil plants, all of which were studied and reported on by F. II. Knowlton, were collected from five different horizons — 15, 60, 70, 150, and 300 feet above the base of the Kootenai formation. The lowest horizon was on Hazlett Creek, where the following species were collected from a dark-colored sandy “School of Mines Quart., vol. 8, July, 1887, p. 329. *> Ain. Jour. Sci., 3d ser., vol. 61, 1891, pp. 191-201, PI. XIV. c Proc. U. S. Nat. Mus., vol. 15, 1892, pp. 487-495, Pis. LXXXII-LXXXIV. rfMon. U. S. Geol. Survey, vol. 48, 1905, pp. 284-315, Pis. LXXI-LXXIII. 54937— Bull. 356—09 3 34 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. shale 45 feet below the coal horizon and 15 to 20 feet above the base of the formation : Cladophlebis heterophylla Fontaine. Thyrsopteris elliptica Fontaine. Zamites articus Goppert. Zamites apertus Newberry (?). Fragmentary plant remains were observed in the dark-colored clay underlying the coal at a number of localities; and a few small collections were made, the largest being from the Meredith mine, on the east side of a small coulee tributary to Geyser Creek, about 6 miles southwest of Geyser, Mont. The following were obtained: Cladophlebis heterophylla Fontaine. Cladophlebis constricta Fontaine. Cladophlebis fisheri Knowlton. Thyrsopteris elliptica Fontaine. Acrostichopteris fimbriata Knowlton. Dryopteris? kootaniensis Knowlton. Adiantum montanense Knowlton. Oleandra graminsefolia Knowlton. Ginkgo sibirica Heer. Podozamites lanceolatus (L. and H.) Schimper. Zamites articus Goppert. Nilsonia schaumburgensis (Dunker) Natliorst. On the north side of Skull Butte, the following fossil plants were obtained from a light-colored impure sandstone about 150 feet above the base of the formation and 86 feet above the coal : Cladophlebis heterophylla Fontaine. Cladophlebis browniana (Dunker) Seward. Protorhipis fisheri Knowlton. Sequoia reichenbachi (Geinitz) Heer. Coniferous leaves? The highest horizon in the Kootenai formation at which plants were collected was on the east side of Spanish Coulee, a small tribu- tary of Smith River in sec. 11, T. 17 N., R. 2 E., where the following were secured : Thyrsopteris elliptica Fontaine. Chiropteris spatulata Newberry. Sequoia gracilis Heer. Zamites apertus Newberry. One mile south of Flood siding, about 5 miles southwest of Great Falls, on the Great Northern Railway between Great Falls and Helena, a collection of plants was made, some of which are listed below: Dryopteris montanensis (Fontaine) Knowlton. Sequoia gracilis Heer. Podozamites nervosa? Newberry. Pterophyllum montanense (Fontaine) Knowlton. STRATIGRAPHY. 35 In the bluffs of Missouri River, near the Boston and Montana smelter, a large collection of Kootenai plants was made by O. C. Mort- son. In this collection representatives of the following species occur: Dryopteris montanensis (Fontaine) Knowlton. Sequoia gracilis Heer. Sequoia ambigua Heer. On the south side of Missouri River, opposite the Boston and Mon- tana smelter, a specimen of Ginkgo sibirica was observed by the writer, but was not collected. The collection of fossil plants obtained from the Kootenai forma- tion in the Great Falls region during the present investigation of the coal resources of the district is not large, hut it is of unusual interest in that it contains a number of species before unknown in the Koo- tenai rocks of the United States, although present in the Canadian beds of this age; it contains also a species of the genus Protorhipis not previously found in North America, as well as some believed to be new to science. In addition to the plants, some fresh-water invertebrates were collected from the upper part of the Kootenai during the investiga- tion. A list is given below: Unio farri Stanton? Unio sp. Corbula sp. Campeloma liarfowtonensis Stanton? Goniobasis ortinanni Stanton? Yiviparus? sp. These fossils are too imperfect for positive identification, but the species with which they are compared occur a few miles south of Harlowton, Mont., in beds that belong to either the Kootenai or the Morrison. The following bibliographic list contains the more important paleobotanical papers published on the Kootenai formation: Dawson, Sir William, On the Mesozoic floras of the Rocky Mountain region of Canada: Trans. Royal Soc. Canada, vol. 3, sec. 4, Pis. I-IV, pp. 1-22. 1885. The name “Kootanie series" is first given and defined in this paper, p. 2. Newberry, J. S.. The Great Falls coal field, Montana: School of Mines Quart., vol. 8, pp. 327-330. ^1887. Dawson, Sir William, Cretaceous floras of the Northwest Territories of Canada: Am. Naturalist, vol. 22, pp. 953-959. 1888. Newberry, J. S., Flora of the Great Falls coal field, Montana: Am. Jour. Sci.. 3d ser., vol. 61, PI. XIV, pp. 191-201. 1891. Dawson, Sir William, Correlation of early Cretaceous floras in Canada and the United States: Trans. Royal Soc. Canada, vol. 10, sec. 4, figs, (in text) 1-16, pp. 79-93. 1892. Fontaine, W. M., Description of some fossil plants from the Great Falls coal field of Montana: Proc. U. S. Nat. Mus., vol. 15, Pis. LXXXII-LXXXIV, pp. 487-495. 1892. 36 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. Ward, L. F.,, and Fontaine, W. M., Flora of the Kootanie formation: Mon. U. S- Geol. Survey, vol. 48, Pis. LXXI-LXXIII, pp. 277-315. 1905. Fontaine, W. M., Notes on some Lower Cretaceous (Kootanie) plants from Mon- tana: Mon. U. S. Geol. Survey, vol. 48, Pis. LXXI-LXXIII, pp. 284-315. 1905. Knowlton, F. H., Description of a collection of Kootenai plants from the Great Falls coal field of Montana: Smithsonian Misc. Coll., vol. 50, pt. 1, pp. 105-128, Pis. XI-XIV. 1907. COLORADO SHALE. General statement . — The rocks overlying the Kootenai formation in this district consist mainly of dark-colored shale with a number of prominent sandstone members in the lower part. This shale and sandstone constitute the well-known Fort Benton formation of the Meek and Hayden upper Missouri River section, the name being derived from the town of Fort Benton, on Missouri River, about 40 miles below Great Falls. The exposures on which the original descriptions were based and by which the stratigraphic limits of the formation were determined lie far to the east in Nebraska. In northeastern Nebraska, along Missouri River, throughout the Black Hills, and along the Rocky Mountain front, the Benton formation is usually underlain by Dakota sandstone and overlain by Niobrara limestone. In the present investigation no evidence was found of the presence of Dakota sandstone as a separate formation in the Great Falls field, nor is the formation here overlain by Niobrara limestone. It is possible that in this region the Niobrara is repre- sented by dark shale, as Stanton has suggested,® and there is some paleontologic evidence in support of this belief. If the upper mem- bers of the shale and sandstone series do represent deposition during Niobrara time, they can not be separated stratigraphically from the underlving Benton. For this reason the rocks which lie between the top of the Kootenai and the base of the Eagle sandstone are de- scribed as the Colorado shale. This name was used in the same sense by Weed in the Fort Benton folio. Character and extent . — The Colorado shale is well developed in this general region, being represented by about 1,600 feet of beds. The entire formation does not occur within the area, but only the lower three-fourths, the upper members being exposed to the north in the higher portions of the Highwood Mountains. In the vicinity of Fort Benton, only a few miles to the northeast, the Colorado is essentially a shale formation with very thin beds of impure sandstone- The Mowry shale member, which constitutes a conspicuous division of the formation to the southeast along the Rocky Mountain front, is present here, but is not conspicuous, owing to the flat dips which prevail throughout the area. Along the south side of the Highwood a Geology of Yellowstone National Park: Mon. U. S. Geol. Survey, vol. 32, 1899, p. 605. Geology and paleontology of the Judith River beds: Bull. U. S. Geol. Survey, No. 257, 1905, p. 11. STRATIGRAPHY. 37 Mountains and in Belt Butte the formation contains a bed of volcanic ash. The rock is pale yellowish gray, weathering white. It resem- bles porcelain and is overlain by rock of similar character and appear- ance. Samples of this rock were collected from Belt Butte and from a*locality about 8 miles northeast of Stanford. Thin sections have been examined by Albert Johannsen, who describes the first as follows: ‘‘Cryptocrystalline in texture. It is very slightly aniso- tropic, as a de vitrified glass might be. There are a few irregular anisotropic patches which are too small to be determined. There is also a little brownish decomposed material. It may be an indu- rated volcanic tuff or rhyolitic glass. 77 The second is described as “a very fine grained, compact glass, consisting almost entirely of angular fragments very slightly devitrified, and a very few r small, irregular grains, apparently of quartz, but too small to be determined. The rock is very homogeneous and uniform in appearance throughout the section. 77 The presence of a bed of volcanic ash in the Colorado shale is a local feature, for it is absent in the western part of the field. Southwest of Great Falls, where the Colorado is well developed, its basal member consists of a soft massive sandstone, somewhat concretionary, about 30 feet thick. Above this sandstone is approx- imately 35 feet of rocks composed largely of dark-colored shale with a few r sandstone beds. This shale is overlain by gray, coarse-grained, massive sandstone containing concretionary layers and an occasional thin bed of soft sandy shale, the whole having a thickness of about 80 feet. Above the sandstone for 300 feet the beds consist mainly of alternating layers of sandstone and shale. These are followed by 700 feet of beds composed of uniformly dark-colored sandy shale, which constitutes the uppermost member of the Colorado as exposed in this field. A good exposure of the lower half of the formation is found in Belt Butte, where the beds consist of alternating layers of massive gray sandstone and dark-colored shale with the volcanic ash member mentioned above present. A section of the beds as exposed on the west side of Belt Butte follows : Section of Colorado shale in Belt Butte , Montana. Feet. Shale, dark gray, sandy, with thin layers of sandstone 80 Sandstone, dark gray 10 Volcanic ash 30 Shale, dark colored, sandy, with thin layers of sandstone 80 Shale, sandy; or impure sandstone 20 Shale, dark, sandy 75 Sandstone, gray; forming belt around Belt Butte 50 Shale, dark, sandy in lower part 125 Shale, dark, sandy; containing massive sandstone members; locally calcareous at top 180 Kootenai formation. 650 88 GEOLOGY OF GREAT S' ALLS COAL FTELD, MONTANA. I'he Colorado shale is exposed in a wide area extending along the south side of the Highwood Mountains from Belt Creek southeastward to the east border of the district, although much of the area, especially the eastern half, is covered by terrace gravel. Its basal sandstone members occupy the summits of Red Butte and continue westward as a plateau capping to the Missouri River valley. Smith River and its tributary Goodwin Coulee cut the basal sandstone of the Colo- rado, exposing the underlying Kootenai rocks. The Colorado shale occupies the surface of the highland lying between Missouri and Sun rivers, also north of these streams across the northern border of the district. Its areal distribution is about equal in extent to that of the Kootenai, as is shown bj^ the geological map (PI. I). Fossils. — Invertebrate fossils were found in the Colorado shale at several localities, notably near Geyser, where collections were made at four different localities at a point 1J miles northwest of Geyser, Inoceramus labiatus Schloth. (?) and fragments of an unidentified Inoceramus were obtained. A mile farther northwest the following o were collected : Inoceramus — large, probably unde- Nucula sp. scribed species. Cardium sp. Leda sp. Prionotropis sp. These fossils have been examined by T. W. Stanton, who regards them of Benton age. The fossils from the last-named locality are believed to represent the upper part of the Colorado shale. A few fragmentary specimens of Inoceramus were found on the west side of Belt Butte, on the south side of Stanford Buttes, and 7 miles northeast of Stanford, Mont. The fossils were collected in all these places at a horizon a few feet below the bed of volcanic ash above referred to. At the north end of Square Butte, which lies about 2 miles west of the area here discussed, fossils were collected at a horizon believed to be near the top of the Colorado. These were Ostrea sp., possibly Gryphsea, and fragments of Scaphites ventricosus M. and H. Fragmentary remains of a swimming saurian, believed by C. W. Gilmore to be a plesiosaur, were collected from a bluish shale under- lying a prominent sandstone member of basal Colorado on the west side of Spanish Coulee, in sec. 10, T. 17 N., R. 2 E. The Colorado shale rests wdtli apparent conformity upon the underlying Kootenai, and is overlain conformably by the Eagle sandstone, the lowest member of the Montana group. Although conformable relations appear to exist between the Kootenai and Colorado formations in this region, the Dakota, which occupies a position between these two formations in other localities, is, as pre- viously stated, believed not to be present. If this is true, there is a hiatus at this contact representing at least several hundred feet of beds. It is possible that Dakota time is here represented by marine sediments not easily separable from the Colorado shale. STRATIGRAPHY. 39 TERTIARY AND QUATERNARY SYSTEMS. TERRACE GRAVEL. General statement . — Throughout a great part of the territory lying east of the Otter Creek divide the plateaus of different levels which occupy the interstream spaces are covered by gravel ; and the inter- mediate slopes, especially those of gentle inclination, are in many places strewn with material which has worked down from the higher terraces. A few isolated areas of terrace deposits are found west of thft divide, notably those between Williams and Otter creeks, on either side of Belt Creek below the town of Belt, and on the south side of the Missouri, below the mouth of Smith River. Smaller areas lie along the sides of the creeks and at low levels in some of the larger valleys, especially Belt Creek. These are generally too small to be shown on the geologic map. To the northwest are terraces believed to be contemporaneous in age with those of the Great Falls field, reaching far out on the plains east of the Levis Range, but these do not extend into the area covered by this report. Character . — The terrace gravel is diversified in character, depend- ing on its location relative to the different portions of the adjoining mountains whence it was derived. Those deposits which occur op- posite the higher portions of the Little Belt Mountains, where crys- talline rocks are exposed, contain a relatively high percentage of igneous rock, but to the east, where sediments from the crest of the mountains and crystalline rocks have not been uncovered, the amount of igneous material in the gravel is small. The deposits in general consist of sand and gravel with local beds of clay. The component parts of the gravel are of varying size, ranging from that of a pea to 10 inches in diameter. In the area bordering the mountains there are some bowlders exceeding a foot in diameter. The pebbles are rounded to subangular, and none were seen which contained striations. Mode of occurrence . — Terrace deposits of three distinct levels are found in the eastern part of the Great Falls region. The highest has been definitely recognized at only one locality — on the summit of Stanford Butte. This deposit, which has been described by Weed a as the Stanford conglomerate, consists of medium to large sized peb- bles, not well assorted, cemented into a firm conglomerate. Rem- nants of this or possibly of some higher terrace gravel are found on some of the prominent points in the hilly zone bordering the Little Belt Mountains, but the correlation of the material of these localities with that of Stanford Butte is by no means certain. The second terrace is about 100 feet below the level of the Stanford conglomerate, and carries one of the most extensive terrace deposits of the district. It occupies the high ridge east of Skull Creek, along Weed, W. II., Geologic Atlas U. S., folio 55, U. S. Geol. Survey, 1899. 40 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. either side of Surprise Creek, in the vicinity of Stanford Butte, and extends far to the east as a prominent topographic feature on either side of Arrow Creek. The third and lowest terrace covers the broad flat of Running Wolf Creek valley east of Stanford, and is also found at low levels on Geyser Creek and its principal tributaries. East of Stanford this terrace is only a few feet above the flood plain of the present valley. The thick- ness of the deposit ranges from 5 to 35 feet in different parts of the field. It lies along either side of the streams, and has smooth sur- faces which slope gently away from the mountains toward the plains. Origin of terraces . — It is apparent from a study of the composition of the gravel deposits that their source was mainly in the Little Belt Mountains to the southwest, but little definite evidence could be ob- tained as to the manner in which they were laid down. It is believed that the gravels were brought down by streams from the Little Belt Mountains, and spread by them over the lower plains country, as their courses were shifted from time to time, but it seems probable that the cause which resulted in the development of the different terrace levels was not normal to the streams of that period, but was accidental. Whether the terraces resulted from uplift in the region, with subsequent rejuvenation of the streams, or from changes in cli- matic conditions is difficult to determine. The latter seems more probable, especially in the case of the more recent terraces, which were probably formed during Pleistocene time. No definite evidence could be found to show that the older terraces were not formed by uplift. Age . — The age of the different gravel terraces in the Great Falls field can not be definitely stated. The two higher terraces are post- Miocene to early Quaternary in age ; the third and smaller subsequent terraces date from the occupation of this area by the Keewatin ice sheet, in Wisconsin time, nearly to the present day. The conclusion regarding the age of the earlier terraces is based on the following considerations: (1) Previous workers in the Little Belt Mountains place the date of the last uplift in this general region at the close of the Miocene. After this period the region was base-leveled. Whether the oldest terrace was formed as a result of this base-leveling or at some later period is not known, but it is certain that it was not earlier than the close of Miocene time. (2) Terrace gravel believed to be contemporaneous with the oldest deposits here described occurs northwest of Great Falls, on the high divide between Sun and Teton rivers, a few miles beyond the area to which this report relates. (3) In the bottom of Sun River valley near Augusta, at least 300 feet below the highest gravel terrace to the north, terminal moraines of mountain glaciers are found. According to Calhoun,® in the region a Calhoun, F. H. H., The Montana lobe of the Keewatin ice sheet : Prof. Paper U. S. Geol. Survey No. 50, 1900, p. 46. STRATIGRAPHY. 41 to the north material derived from local glaciers is overlain by de- posits of the continental ice sheet, and from this and other observa- tions made throughout the general region to the north he regards the local glaciers of the Lewis Range as but slightly older than those of the Keewatin ice sheet, which occupied this area during Wisconsin time. Prior to both the local and continental glaciation of this re- gion, therefore, a period must have elapsed sufficient for the erosion of Sun River valley nearly to its present stage after the gravel cap- ping the high divide between Sun and Teton rivers was laid down. The erosion of this valley required considerable time, so that it seems probable that the high terrace gravels north of Sun River, which are believed to be contemporaneous with the older terrace gravels in the area described, should be regarded as of early Quaternary or possibly late Tertiary age. GLACIAL DEPOSITS. General statement . — Glacial deposits of Wisconsin age occupy a considerable area throughout the Great Falls region. The terminal moraine of the Montana lobe of the Keewatin ice sheet enters the dis- trict at a point about 10 miles due northeast of Great Falls, extending southward across Missouri River to Sand Coulee near Gerber station. At this point it makes a sharp bend to the east and continues thus past the head of Red Coulee, thence northeastward to Belt Creek, where it crosses the northeastern margin of the district. Its location and extent, as first worked out by Calhoun® and later examined more in detail by the writer, are shown on the geologic map (PI. I). In addition to the morainal deposits, extensive lake sediments were laid down in front of the terminal moraine during the occupation of this general region by the ice. Much of this material has been removed by postglacial erosion, especially on the higher lands, but all the larger valleys in front of the moraine are filled with it. Lake deposits of two different periods, an earlier and a later, have been recognized by gla- ciologists in this region. The limits of the earlier lake can be ascer- tained only by bowlders lodged on the summits of the plateaus, but a considerable part of the deposits of the more recent lake still remains as a filling in the larger valleys. Drift . — The drift consists of crystalline erratics, small pebbles, sedimentary rocks, and a matrix of sand and clay. The greater part of the material, however, is a sandy clay of dull-green color, generally unstratified, %vhich stands in vertical faces where trenched by streams. The character of the rocks composing the drift has been studied in detail by Calhoun, 6 who describes them as follows: The crystalline erratics are of such variety as to furnish specimens of the whole rock series. In a small area, not over 5 square yards in extent, the following rocks were found: Limestone, sandstone, shale, coal, granites (both fine and coarse grained and a Op. cit., PI. V. &Op. cit., p. 27. 42 GEOLOGY OF GREAT FALLS COAL FTELD, MONTANA. with different percentages of quartz and feldspar), syenites, diorites, basalts, and hornblende, mica, and garnetiferous schist, and all gradations between these and gneissic rocks. The granite and the syenite rocks predominate. Basalt and rocks containing a large proportion of the ferromagnesian minerals are not so common. In his general study of the Montana lobe of the Keewatin ice sheet Calhoun observes little variation in the nature of the bowlders throughout the length of the moraine. Limestone bowlders are more common in the northern part and sandstone bowlders in the southern part, but the character of the crystalline bowlders remains the same. The small pebbles which make up a varying proportion of the bowl- ders of the drift are believed by Calhoun to be of mountain origin, having been derived from a quartzite gravel formation to the north- east. Crystalline bowlders are generally common on the surface of the drift, but in the body of the material not many are found. Here even smaller pebbles sparingly occur. An explanation of the position of these bowlders in the drift is given by It. D. Salisbury.® The thick- ness of the drift within the area treated is variable, the maximum observed being between 150 and 200 feet. Lake sediments . — The lake deposits are mainly of two kinds — large bowlders deposited on the high land by floating ice in waters of the Fig. 1.— Ideal cross section showing relations between the two lake deposits in Missouri River val- ley west of Great Falls, c, Level of the more extended lake; d, level of the smaller lake. After Calhoun. older and more extensive lake and finely laminated sandy clay laid down by the smaller lake in the larger valleys of the Great Falls region (figs. 1 and 2). A detailed examination of the composition of these lake sediments was not made by the writer, but they were care- fully studied by Calhoun, whose description is here given. 6 The deposits of the more restricted lake consist of a finely laminated clay which when dry is hard and cleaves like shale. When wet it becomes soft and pliable, and would make an excellent molding clay. Interstratified with the clay are small crystal- line pebbles one-fourth to one-half inch in thickness. They usually consist of quartz or feldspar crystals, or of small fragments containing several minerals, showing that the rock from which they were derived was granite, syenite, or basalt. Very seldom a large crystalline bowlder is found embedded in the clay. The maximum thickness of this clay within the area treated was not ascertained, but along the Missouri near Ulm Calhoun observed c a thickness of 40 feet, the material containing the small crystalline peb- bles characteristic of the formation farther north. Its distribution is not shown separately on the geologic map, as it is included with the alluvium. The accompanying ideal sections (figs. 1 and 2) by the U Jour. Geology, vol. 8, 1900, pp. 426-432. f>Op. cit., pp. 30-31. ‘ Op. cit., p. 31. STRATIGRAPHY. 48 above-named author® illustrate the relation of the two lake deposits to the drift and ice dam. ALLUVIUM. General statement . — The alluvial deposits of the Great Falls region present rather unusual features. They occur intimately associated with glacial-lake sediments of the Keewatin ice sheet, and on the geologic map are not differentiated from those sediments. As pre- viously stated, during the occupation of the region by the continental glaciers the waters of the Missouri and its larger tributaries were dammed and an extensive lake existed first in front of the ice and later in front of the terminal moraine. Sediments of this lake in its various stages filled all the larger valleys in the vicinity of Great Falls. Although much of the material constituting these sediments was brought down by streams from adjoining mountainous region, and to this extent they correspond to normal alluvial deposits along any large stream, a certain amount was contributed by the melting ice from the glacier. The alluvium, therefore, of the Missouri and its larger tributaries in this immediate district has been derived from Fig. 2. — Ideal longitudinal section showing the relation of the two lake deposits shown in fig. 1 to the drift dam and the ice dam. a, Ice edge; b, moraine; c, level of the more extended lake; d, level of the smaller lake. After Calhoun. two distinct sources. That brought in by the river may be regarded as local and that by the glacier as foreign. Character and extent . — The alluvium of the Missouri, together with that of Sun and Smith rivers, its principal tributaries, ranges from half a mile to 3 miles in width. It consists mainly of fine silt and sand, with local beds of clay and gravel. Light colors prevail throughout the material. F rom the base of the Big Belt Mountains northeastward to Great Falls the Missouri meanders through a wide flood plain of an old valley, but east of Great Falls it flows through a narrow valley which is much younger and in which only small detached areas of alluvium are found. Alluvial deposits of small extent occur along Belt Creek and all the minor streams, but these are not shown on the geologic map. DUNE SAND. Character and extent . — Deposits of dune sand occupy a number of small areas in the vicinity of Great Falls. They are confined mainly to the Missouri River valley, but some are found on the lower plateaus bordering the streams. These areas, though small, present the characteristic dune-sand topography of hillocks and basins with no 4 «Op. cit., p. 30. 44 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. developed drainage.' The' dunes range from 10 to 20 feet in width. They are of recent origin and in many places travel before the wind. Perhaps the largest accumulation of these deposits occurs about 1 mile southeast of Great Falls, on a plateau of the Kootenai rocks which lies approximately 100 feet above the town. Here a belt of low sand hills nearly one-half mile in width extends for 1 1 miles in a north- easterly direction. Another noteworthy dune area is on the west side of the Missouri River valley about 4 miles above the mouth of Sand Coulee. Smaller areas are to be found in the larger bends of Missouri River between Great Falls and Cascade. In the valley on the west side of Smith River, near the confluence of that stream with the Missouri, there are deposits of sand which have been blown about by the wind but have not been formed into distinct dunes. At many places throughout the flood plain of the Missouri sagebrush and other small shrubs hold the sandy soil about their roots and collect^&d- ditional material blown about by small wind currents to suoter an extent that mounds 1 to 2 feet high are built up about each bush, giving the appearance of miniature dune-sand topography. The dis- tribution of the eolian deposits is not shown on the map. Source . — The dune sand of the Great Falls region is derived prin- cipally from alluvial deposits of the Missouri Valley. It consists mainly of loose, fine-grained sand which in many places is not covered by vegetation, so that it is readily caught up by the wind and carried about. The sand thus transported is generally redeposited in the form of dunes in the valley or on the slopes of the adjoining highlands, but sometimes it is blown out of the valley and lodged on the bluffs above. It is believed that the deposits south of Great Falls originated in this way. IGNEOUS ROCKS. Igneous rocks occur in the Great Falls region mainly in the form of dikes and sheets, although stocks and unexposed laccoliths are also to be found. The dike rock of most common occurrence is a basalt, of which there are a number of varieties. It is usually very dark colored and dense, presenting on the surface a spotted appearance, due to the presence of large crystals of basaltic augite. Much of the intruded material is sufficiently hard to resist weathering better than the soft sedimentary rocks and stands out as an irregular wall or ridge. Less commonly the intrusive material is soft and crumbles easily, so that it can be traced only by lines of green vegetation growing on the surface of the decomposed rock. Rocky Ridge is formed by one of the harder basaltic dikes extending from a point near the base of Highwood Mountains southwest to V illiams Creek. The intrusive rocks in this region do not, so far as known, cut or disturb to any considerable extent the areas underlain by workable STRATIGRAPHY. 45 coal, and consequently they are not of very great importance in the present discussion. In several places, however, intrusives appear at the surface on the margin of areas believed to be underlain by workable coal, notably on the northern border of the Otter Creek coal area, near the mouth of Williams Creek, on the upper part of Hazlett Creek, on the west side of the Sage Creek coal area, and on the northeast side of Belt Butte along the east side of the Sand Coulee coal area. In none of these localities can the intrusive rocks be traced by surface outcrops into the area underlain by workable coal; but they may possibly continue, although unexposed, sufficiently far to cut and disturb valuable coal beds. Xo special examination was jnade of the petrographic character of the intrusive rock in the eastern part of the Great Falls field, for it forms a portion of a large petr^raphie province of central Montana which has been studied in a detailed and comprehensive way by Weed and Pirsson. For a more extensive account of these rocks and of the larger petrographic prov- inc%*if which they form a part, the reader is referred to the following publications: Weed, W. H. Two Montana coal fields: Bull. Geol. Soc. America, vol. 3, 1892, pp. 301-330. Little Belt Mountains folio (Xo. 56), Geologic Atlas U. S., U. S. Geol. Survey, 1899. Geology of the Little Belt Mountains, Montana: Twentieth Ann. Rept. U. S. Geol. Survey, pt. 3, 1900, pp. 271-461. Weed, W. H., and Pirsson, L. Y. Igneous rocks of Yogo Peak, Montana: Am. Jour. Sci., 3d ser., vol. 50, 1895, pp. 467^79. Highwood Mountains of Montana: Bull. Geol. Soc. America, vol. 6, 1895, pp. 389-422. Geology of the Castle Mountain mining district, Montana: Bull. U. S. Geol. Survey, No. 139, 1896. The Bearpaw Mountains, Montana: Am. Jour. Sci., 4th ser., vol.. 1 1896, pp. 283-301, 351-362; vol. 2, 1896, pp. 136-148, 188-199. Missourite, a new leucite rock from the Highwood Mountains of Montana: Am. Jour. Sci., 4th ser., vol. 2, 1896, pp. 315-323. Geology of the Little Rocky Mountains: Jour. Geolog}’, vol. 4, 1896, pp. 399-428. Geology and mineral resources of the Judith Mountains of Montana: Eighteenth Ann. Rept. U. S. Geol. Survey, pt. 3, 1898, pp. 446-616. Pirsson, L. V. Petrography of the igneous rocks of the Little Belt Mountains, Mon- tana: Twentieth Ann. Rept. U. S. Geol. Survey, pt. 3, 1900, pp. 463-581. Petrography and geology of the igneous rocks of the Highwood Mountains, Montana: Bull. U. S. Geol. Survey No. 237, 1905. In the vicinity of Cascade, Mont., on the eastern side of Missouri River, in sec. 20, T. 17 N., R. 1 E., a large dike extends into the area from the main bed of intrusive rock constituting the north end of the Big Belt Mountains. As this dike radiates from an igneous mass at a considerable distance from those above described, samples from it were collected for the purpose of having thin sections prepared 46 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. and studied. These sections have been examined by Albert Johann- sen, of the Geological Survey, whose preliminary report is as follows: Tentative name: Andesite porphyry with latite affinities. Megascopic: A dark-gray porphyritic rock, weathering a dirty yellow. The black phenocrysts, up to one-eighth inch in diameter, become very pronounced on the weathered surface. Microscopic: Porphyritic; about one-fifth phenocrysts. The groundmass has an intersertal texture in which the irregular areas are of a dirty-brown serpentine. The phenocrysts, which are chiefly augite, are generally in broad, lath-shaped sections. A few of the feldspar crystals of the groundmass are larger than the remainder and may be classed with the phenocrysts. The groundmass consists of dirty yellowish-brown serpentine, less augite, about the same amount of magnetite, much less orthoclase, and some pseudomorphs, now serpentine, which have the form of olivine. The feld- spar consists of plagioclase and orthoclase; the plagioclase varies in composition from andesine to andesine labradorite. Apparently none is more basic than Ab 50 , An 50 . The index of refraction is ±551. MET AMORPHIC ROCKS. Very few metamorphic rocks are found in the plains portion of the Great Falls region, although in the mountainous districts surrounding the field the sedimentary rocks have been highly metamorphosed by intrusive dikes, sheets, and laccoliths. The Highwood Mountains bordering this field on the north have been caused by igneous intru- sion in Cretaceous rocks, which were metamorphosed to such an extent that they have resisted subsequent erosion and now stand out from the surrounding plains as a cluster of high peaks. Intrusions in the form of stocks and laccoliths are more or less common along the base of the adjoining mountain ranges. From some of these intruded rock masses the overlying sediments have been removed, exposing a central core of igneous rock, around which contact-meta- morphic phenomena are well exhibited. A good illustration of these conditions is found on the east side of Little Otter Creek, about 3 miles south of Mann, outside of the area here discussed. As previously stated, intrusive rock in this district is most com- monly found in the form of dikes. In most localities these have metamorphosed the sediments into which they were intruded for some distance back from the contact, converting sandstone into quartzite and shale into slate. Phenomena of this character were observed at several places, notably on the north side of the Big Belt Mountains, about 7 miles southwest of Orr, in the vicinity of Rocky Ridge, and throughout that portion of the field which lies east of Stanford. No places were observed where the intrusives had cut the workable coals and thereby altered them by metamorphism along the contact. For this reason no special study was made of the character of the contact-metamorphic rocks of the field. It is highly probable that the intrusives which cut the sediments on the northeast side of Belt Butte have had some effect on the Kootenai coals of that STRUCTURE. 47 district, providing they extend so far east, but as there are no expo- sures of the coal beds the phenomena could not be observed. There are also, on the upper part of Hazlett Creek, dikes which in their northeast extension may cut and alter by metamorphism workable coals, but these dikes could not be traced on the surface into the coal area. The same is true of the dike forming Rocky Ridge, which extends southward from Highwood Mountains, but disappears at the northern edge of the Otter Creek coal area. STRUCTURE. PLAINS PROVINCE. GENERAL CONDITIONS. Throughout the plains portion of the region described the structure is relatively simple. The rocks as a rule lie nearly horizontal, dipping with a small angle to the north and east, away from the mountains, but in the mountainous portion the structure is more complex. Al- though low dips of 3° to 5° prevail throughout the plains province, and the district is one of little disturbance, the rocks on closer examination are found to be gently folded into a series of shallow synclines and low anticlines. This structural feature is scarcely perceptible to the cas- ual observer, being revealed only by a careful examination of the beds exposed along the sides of the larger streams, such as Otter and Belt creeks and Smith River and its principal tributaries. The major axes of these folds appear to be roughly parallel to the Little Belt Moun- tains uplift, but the folds are only of slight magnitude and the indi- vidual warps are broad. The largest and most perceptible of the synclinal depressions crosses Otter Creek between the mouth of Wil- liams Creek and the Nollar mine. Its effect is to carry the coal-bear- ing rocks of the Otter Creek area about 100 feet below Otter Creek valley for a distance of 3 or 4 miles. The slight deformation of the coal-bearing rocks has had an impor- tant bearing on the development of the coal beds of this field. Wher- ever stream valleys cross the coal-bearing areas and cut sufficiently deep to expose the coal, they produce favorable conditions for mining. Owing to the horizontal position of the beds, entries can be driven for long distances nearly at right angles to the direction of the dip, which is in general to the north, without producing an appreciable lift in the haulage of the coal. The gentle northward dip of the coal-bearing rocks can be turned to advantage in mining by driving the main entry at an angle greater than 90° with the direction of the dip, thus causing the entry to extend up the dip sufficiently to produce natural drain- age of the workings. Though in general the rocks lie nearly hori- zontal throughout the Great Falls field, there are minor undulations in the strata which are too local to be observed on the surface, but which 48 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. are shown in the maps of the mine workings. Some of these cause more or less difficulty in mine haulage, making it necessary to use special appliances to fit the topographic conditions in the mine. DOMES. Local doming of the strata, due to laccolithic intrusion of igneous rock, is more or less common along the north side of the Little Belt Mountains and in the vicinity of the Judith Mountains, farther east. Skull Butte, in the plains province at the east end of the district, is with- out doubt a domal uplift of this character. It is nearly circular in out- line, its greatest diameter being about 1J miles, and its quaquaversal dips ranging from 20° to 30°. Erosion of its center has not advanced sufficiently to uncover igneous rocks. This uplift exposes the coal in the steeply dipping beds about its base. In the vicinity of Stockett local uplift and erosion occurred prior to the deposition of Jurassic sediments, as is shown by the unconformable relations of Jurassic sandstone and Madison limestone. Exposures of the limestone occur in which the strata are tilted and eroded, with Jurassic sandstone deposited across the upturned ends. The strongest dip of the limestone beds seen was about 10°. The various forma- tions in this vicinity are perceptibly thinner than elsewhere, a strati- graphic feature probably due to the presence of the dome during the deposition of these sediments. The unconformable relations of the Carboniferous and Jurassic formations, and the moderately steep dips of the latter as exhibited in Sand Coulee, about 2 miles east of Stock- ett, are shown in PI. YI. This doming of the Carboniferous rocks in the Stockett region is probably not of wide extent, but its exact limits can not be ascertained owing to the lack of exposures. Its north- south dimension, as shown by outcrops along Sand Coulee, is about 4^ miles, but its east and west boundaries are not known. At Stockett and along Sand Coulee valley, owing to the thinning of the Jurassic and Lower Cretaceous formations, also to the absence of the Quadrant in the vicinity of the dome, the coal horizon occurs only about 150 feet above the Madison limestone, which is exposed in the bottom of the valley. This feature might be misleading to prospectors who are not familiar with the local conditions about Stockett, for in other parts of the Great Falls coal field, especially along Belt Creek and in the Otter and Sage Creek areas, the coal bed is separated from the Madison limestone by about 650 feet of rock. At the head of Ming Coulee, where coal of workable thickness is exposed, the beds dip steeply to the northwest. These local dips are due to a large dome farther south, outside of the area treated in this report. The Quadrant formation is also absent, causing the coal bed to occur about 250 feet above the top of the Madison. STRUCTURE. 49 On Boston Coulee, about 2| miles west of Eden, a local dome of the strata exposes the coal-bearing bed along Boston Coulee for about 1J miles, and also to the southward up a small tributary of that coulee for an equal distance. This small uplift, which causes the coal outcrop to take a T-shaped form, is shown on the coal map (PI. II). FAULTS. No large faults occur within the area here discussed, but minor faults are not uncommon, especially in the vicinity of Belt and Stock- ett. The throw of these faults ranges from 5 to 20 feet, and their presence is usually difficult to detect on the surface. They are gen- erally first encountered by miners who are working the coal bed, and in some places their presence has caused considerable difficulty in min- ing operations. At Belt, on the west side of Belt Creek, such a fault extends nearly west for about 1J miles, displacing the coal bed a few feet and causing difficulty in operations along the north side of the underground workings of the Anaconda Copper Mining Company’s mine. In Armington Coulee, about half a mile above the mouth, a sharp fold in the beds trends northward toward Belt Butte. The beds may possibly be more or less fractured along its axis, but exposures at this place were inadequate for positive determination of this point. Other small displacements have been reported from some of the smaller mines along the’ east side of Belt Creek in the vicinity of Arm- ington and Belt, notably in the Richardson mine and to a less degree in the Smauch and Millard mines, but these faults appear not to cause any appreciable displacement of the sediments at the surface. On the north side of Stockett a small fault in the Madison limestone has a throw of about 15 feet, extending east and west. The Cottonwood Coal Company reports that a small north-south fault in the coal-bear- ing rocks was encountered in mining about three-fourths of a mile east of the town; but no evidence of this fault was observed on the surface. The minor faults throughout the Great Falls coal field are not shown on the geologic map. It is possible that many such small faults are scattered over the field and will be discovered on more extensive development of the coal deposits, but it is difficult if not impossible to locate them, owing to the fact that their throw is generally insufficient to be perceptible on the surface. LITTLE BELT MOUNTAINS. The general structure of the Little Belt Mountains, which border this area on the south, is that of an anticlinal uplift with sharply dip- ping sides and a flat summit. In the central portion of the range the stratified rocks lie nearly horizontal, but along the northern flank of 54937— Bull. 356—09 4 50 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. the uplift, as found on the head of Geyser Creek, the limestone dips at an angle of 15° to 20° toward the lower plains country. As previously stated, the simple structure of the northern part of the uplift has been considerably modified by the intrusion of igneous rocks in the form of laccoliths, which have caused local doming of the strata in many places. Only one of these laccolithie domes lies within the area de- scribed, but there are others, such as those east of Kibby and in the head of Dry Wolf Creek, whose marginal structure extends into the district. In the vicinity of the larger intruded masses of igneous rock the dips are in many places steep and variable, but in that portion of the mountain front where local intrusions have not disturbed the strata, they dip away normally from the uplift at angles of 6° to 12°, lessening gradually toward the lower plains country. HIGHWOOD MOUNTAINS. The Highwood Mountains, which border on the north the east end of the area described in this report, are structurally of a different type from the Little Belt Range. They consist of a group of isolated peaks, which were formed by igneous intrusions in Cretaceous rocks that were horizontally bedded or slightly inclined toward the east. Subsequent to this intrusion stream erosion carved out this cluster of peaks from the surrounding plains. ECONOMIC GEOLOGY. GENERAL STATEMENT. The mineral resources of the area treated in this report are some- what varied, but the principal one at present is coal. Fire clay of a superior quality is found in beds of workable thickness along Belt Creek and its tributaries, and at many places throughout the district raw materials suitable for the manufacture of Portland cement can be obtained. Gypsum deposits occur at different horizons in the Quadrant formation near Riceville, and at Goodman this mineral has been mined in a small way for a number of years. Building stones of different varieties, also limestone, are common in many parts of the field. Sand and gravel can usually be obtained locally. Iron pyrite is mined as a by-product with the coal and shipped to Great Falls, where it is used in the process of pyritic smelting. COAL. GEOLOGIC OCCURRENCE. Throughout the Great Falls coal field the coal occurs in the lower part of the Kootenai, or Lower Cretaceous rocks, mainly at a horizon about 60 feet above the base of the formation. Coal of workable thickness is not continuous, however, at this horizon, but varies locally. COAL. 51 This irregularity of occurrence is a characteristic feature of the beds of this field which was early observed in the investigation, and an effort was made to ascertain as far as possible, from a study of the outcrop, the limits of the areas underlain by workable coal. These coal areas, or basins, as they have previously been designated by Weed,® are three in number and include a total area of approximately 334 square miles. The largest, comprising about 231 square miles, lies south of Great Falls, extending from a point a short distance east of Belt Creek beyond Smith River. (See PI. II.) It is possible that the coals of this basin continue to the south throughout the territory lying between the Little and Big Belt mountains, but no examination was made of this region. The district examined is drained by Sand Coulee and its tributaries, and is known as the Sand Coulee area. To the east the next district underlain by coal of commercial impor- tance lies between Little Otter and Geyser creeks, and is designated the Otter Creek area; it is the smallest coal area in the field, includ- ing only about 37 square miles. Still farther east, in the vicinity of Skull Butte, there is a third coal area, which, owing to its nearness to Sage Creek, the main drainage channel of the district, is called the Sage Creek area. It includes about 66 square miles. SAND COULEE AREA. LOCATION AND EXTENT. The Sand Coulee coal area, which lies south of Great Falls, is 6 miles wide and from 30 to 40 miles long. The exact limits of the area underlain by workable coal are difficult to determine, for it is only along the valleys of streams that cross the area, such as Belt Creek, Sand Coulee, and Smith River and their tributaries, that the coal bed can be studied with respect to its disposition to thicken or thin in any given direction. In the plateau district between these valleys the coal is concealed by 200 to 300 feet of overlying Kootenai rocks, wffiich the smaller streams traversing the plateaus have not cut down sufficiently to expose the coals. As the rocks dip gently away from the mountains, the outcrop of the coal bed extending across the plateau from one stream valley to another occurs far up the slope in the foothill zone, where the coal is usually represented by a thin bed of carbonaceous shale. Under these conditions it is apparent that the width of the coal basin can only be inferred from the thickness of the beds along the stream valleys. As these valleys are more or less widely separated, the lateral extent of the coal area in the plateau region is largely conjectural. Along Belt Creek, which crosses the east end of the area, the coal bed thins rapidly to the south and becomes shaly at a point near the « Weed, W. H., Bull. Geol. Soc. America, vol. 3, 1892, pp. 301-330, 52 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. mouth of Otter Creek. Toward the north the same is true, although in a less marked degree, to a point a short distance above the mouth of Little Belt Creek, where the dip of the rock carries the. coal beneath the river. The bed is thickest in the vicinity of Armington and Belt, and in either direction from this zone there is a perceptible thinning. The eastern border of the workable coal area can not be definitely determined, for the coal east of Belt is not exposed, but along the lower part of Otter Creek the workable bed thins rapidly to the east, a condition which is believed to indicate that the eastern limit of the workable coal should be placed not more than 2 miles east of Belt Creek. According to exposures along Sand Coulee, the coal bed thins to the south, near the northern line of T. 18 N. ; and to the north in sec. 2, T. 19 N., R. 4 E., it is only a few inches thick. The bed reaches its maximum thickness between Straight and Giffen coulees, where the larger coal mines are located. In the Smith River valley, near the mouth of Hound Creek, the coal bed has a good workable thick- ness, which it maintains toward the north, possibly with slight thin- ning as far as sec. 1, T. 17 N., R. 2 E., where the bed passes beneath the river. How far workable coal extends northwest of this point is not known, but it seems probable that it continues for at least 2 or 3 miles. The southern limit of the Sand Coulee area was not ascer- tained, for the investigation did not extend beyond the southern border of T. 17 N., where a local fold of the strata carries the coal beneath the river; as it is of workable thickness at the southernmost point examined, it may possibly continue thus for some distance. On upper Ming Coulee the coal bed has a maximum thickness of 8 feet, but 2 miles farther up this stream the dips are steep and the bed occupies the summits of high hills, where the covering is thin and the coal more or less shaly. Along the north side of the wagon road leading from Ming Coulee to Rocky Coulee the coal bed has been prospected at many places, especially in secs. 21, 22, and 14, T. 17 N., R. 3 E. In most of these prospects the coal horizon was marked by only a few inches of carbonaceous shale, which locally thickens and in one place becomes nearly workable. From these observations it is believed that the southern limit of the Sand Coulee area in this part of the field lies some distance north of the wagon road. The limits of this area as based on the evidence are shown on PL II. CHARACTER AND THICKNESS OF COAL BED. The Sand Coulee area is underlain by one coal bed of commercial importance. In this bed, consisting of coal interbedded with layers of bone, shale, and clay, the coal content ranges in thickness from 6 to 14 feet in different parts of the field. At Belt, in the northeast end of the area, where the bed has been opened at many places, the COAL. 53 average thickness of twenty-six measured sections is 4 feet 7 inches. At Sand Coulee fourteen measured sections give an average thickness of 8 feet 7 inches, and along Smith River, where fewer openings have been made, an average of five sections shows a total thickness of 7 feet 6 inches of coal. In the vicinity of Belt the coal is divided into three distinct benches — a lower, middle, and upper. The lower and upper benches are in many places about equal in thickness, the middle bench being considerably thinner. (See PL VIII.) At Sand Coulee the coal bed generally occurs in two principal benches, the upper being much thicker than the lower. (See PI. X.) Above the uppermost bench worked, however, there are in some places, notably in the Smith River district, two higher layers of coal which have a maximum measured thickness of 5 feet 8 inches. From a comparison of the average thickness, number, and order of the various coal benches in the Belt, Sand Coulee, and Smith River mining districts, it is apparent that the coals of this basin are of broadly lenticular character and it seems probable that the total thickness of coal contained in the coal-bearing zone is greatest in the Sand Coulee mining district. Graphic sections of the coal in the Sand Coulee, Otter, and Sage Creek areas are shown in Pis. X-XII. In the following discussion of the coals of these areas individual sections are referred to by num- bers corresponding to those used on these plates. DEVELOPMENT. Development of the coal resources of the Great Falls coal field was first begun in the Sand Coulee basin at Belt, where, in 1876, a small mine was opened, the coal being shipped overland to Fort Benton, a town situated near the head of navigation on Missouri River. For the first few years the coal output of this field was small, but with the opening of mines at Sand Coulee, on Smith River, which took place a few years later, the amount was increased. In 1885 the combined production of the Belt and Sand Coulee mines was 1,900 tons, of which 1,200 were from the Belt mines. During the follow- ing year the output of these two localities amounted to only 1,400 tons, the greater part being supplied by the Sand Coulee mines. The reports on Cascade County for 1887 give a relatively small yield, but during the following year, with the completion of railroad facilities to Sand Coulee, the total coal production of the region was mate- rially increased. From 1888 to 1892 the annual coal output of the Sand Coulee basin grew steadily with the improvements made in the facilities for handling coal at the Sand Coulee mines; during 1893 the total production of the region increased over 100 per cent. Since 1880, when the first systematic record of the coal production of Montana was kept, Cascade County has been one of the largest pro- 54 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. (hieing counties in the State. Its relative output, with respect to that of the State as a whole, is shown in the following table: Coal production of Montana and Cascade County from 1880 to 1906, inclusive, a [Short tons.] Y ear. Montana. Cascade County. 1880 224 5,000 10, 000 19, 795 80, 376 86, 440 49, 846 10, 202 41, 467 363, 301 517, 477 541, 861 564, 648 892, 309 927, 395 1881 1882 1883 1884 1885 1,900 1,400 1886 1887 1888 4, 600 166, 480 200, 435 198, 107 242, 120 516, 460 638, 960 1889 1890 1891 1892 1893 1894 Year. j Montana. Cascade County. 1895 1,504,193 1, 543, 445 1,647,882 1,479,803 1,496,451 1,661,775 1,396,081 1,560,823 1,488, 810 1,358,919 1,643,832 1,838,635 713 877 1896 1, 10l| 298 1, 138, 590 988, 821 965,378 1,123,395 789, 407 761, 572 733 064 1897 1898 1899 1900 1901 1902 1903 1904 599’ 158 826, 026 991, 417 1905 1906 Total 22, 730, 990 12, 702, 465 « Mineral Resources U. S., 1880 to 1906, inclusive, U. S. Geol. Survey. Although at the present time coal prospects and small mines are located at many different places throughout the Sand Coulee area, development is confined chiefly to three localities where stream val- leys crossing the district cut and expose the coal-bearing rocks. These districts of principal development are along Belt Creek, Sand Coulee, and Smith River. BELT CREEK MINES. GENERAL STATEMENT. Along Belt Creek and its tributaries near the town of Belt the coal bed has been extensively prospected and a number of mines are now being operated. The mine of the Anaconda Copper Mining Company is the largest in the district, but there are four smaller ones which are worked continuously, and seven abandoned mines, some of which have produced considerable coal in the past. Prospecting has been extensive, especially along Neel Creek, on either side of Belt Creek, and in Armington Coulee. A number of diamond-drill prospect holes have been bored by the larger companies on the plateau west of Belt Creek in order to determine the character of the coal bed under- lying their holdings. The location of the mines are shown on PI. II; sections of the coal beds are shown on PI. VIII. MINES OPERATED. Anaconda Copper Mining ' Company mine . — The mine owned and operated by the Anaconda Copper Mining Company, of Anaconda, Mont., is located on the west side of Belt Creek, at the town of Belt. (See PI. IX.) The principal coal holdings of the company, which U. S. GEOLOGICAL SURVEY BULLETIN NO. 356 PL. VIII BELT CREEK DISTRICT Boston & Montana Richardson mine mine, lOO'from Schmauch mine Millard mine Clingan mine 24 Hill mine at Armington mouth of main entry ne ar Belt 22 ' at Belt l8’/z 5+2 "t [16" 3 | 12"+46Va"=58V2" | 11 12+2 8X2 4" 8V2"+ 64 Vs"- 63 10 Anaconda Ck>pper ....,, Mining Co. mine 16 + 61 /z -7T /2 mm ivz 1 ggg 8"+54V 2 "=62V2" 12 1/2 6 1 / 2 "+64"=70 1 /2" 13 Anaconda Copper Mining Co. mine 11 14 17"+ 44"= 61" 12 Anaconda Copper Mining Co. mine between Nos. 18 n^r fault at end 15 Anaconda Copper Room 2, No .17 Anaconda Copper and 19 ent nes 18 of N o. 16 e ntry Anaconda Copper Mining Co. mine ent ry, sou th Mining Co mine ““ ■I Mining Co. mine end of No. 18 — - - •iflGI .. No. 13 entry, south entry Herman & Powell mine near Armington No. 13 entry, south I 20 16' 1 2.3" .34' 12"+58"=70" 8"+72"=S 35" 17 "+57"= 74" 11+71= 82 Anaconda Copper Anaconda Copper Mining Co. mine Mining Co. mine No. 18 entry, north No. 9 entry, south 16*4" 3>/2' 4*4" I 7V 2 "+55"=62V2" 121/2 .^ 65V2 . SMITH RIVER DISTRICT 65 , 64 Love mine 75 from Love mine 66 mouth of main entry end of main entry Bickett mine 10 " i 5 2"B- 7"+ 58"= 4"+ 62"= 66" Gibson mine 8"+86"=93' Impure or bony coal 14" 38"+104"=142" 3"+55"=58" Thickness of coal shown to right of sections Thickness of waste shown to left of sections Vertical scale, 1 inch= 5 feet SECTIONS OF COAL IN BELT CREEK AND SMITH RIVER DISTRICTS, MONT. COAL. 55 comprise several acres, lie in secs. 26 and 27, T. 19 N., R. 6 E. This mine was first opened in 1895, and has been in continuous operation since that time. At present the company employs a large force of men and produces a considerable tonnage. The mine, however, is not worked at its full capacity, the output being controlled by the requirements of the company’s plant at Anaconda, a point to which much of the coal is shipped. The bed at this place has an average thickness of 6 feet, including partings, and occurs in three benches. The lowest bench is about 2 feet 6 inches thick, and is overlain by 2 to 4 inches of bone, followed by the middle bench, which is usually about 7 inches thick. Above this 7-inch layer occurs bone parting 3 to 8 inches thick, followed by a bed of coal 1 to 3 feet thick, constituting the uppermost bench. There appears to be little difference in the physical properties of the coal in the different benches. The bed usually has a shale roof and floor and lies nearly horizontal, dipping only slightly to the north. Sulphur in the form of pyrite nodules occurs in all the benches. A number of graphic sections of the coal bed in this mine are shown in PI. VIII. The underground workings of the mine are very extensive. The main entry has been driven for about 1J miles from the outcrop, with numerous side entries to the north and south one-half mile or more in length. The entire workings cover an area of about 600 acres. The coal is taken out by the room-and-pillar system and brought to the surface by cable haulage. The mine is provided with a double entry, and ventilation is effected by a large fan located near the entrance. Electric lighting is used only in the main entries, and the water is removed by large pumps. Owing to the large amount of impurities present in the bed it is necessary -to wash the machine-mined coal. The method employed is as follows: The coal is carried from the mine in pit cars having a capacity ranging from 2 to 2 \ tons each, by means of a cable and tail rope. A trip consists of 48 cars, which on arriving at the mouth of the mine are uncoupled and allowed to run one by one down a gravity incline from which the car is switched onto one of three tipples, according to the character of the coal it contains. After the cars are unloaded they are gathered again on a single track and returned to the mine. The tipple over which the hand-mined coal is dumped is connected directly by chute to the railroad cars below. The two remaining tipples are connected with a heavy sharp-toothed crusher by long chutes, which are sufficiently large to serve as temporary storage bins. At the crusher all the machine-mined coal is reduced to a small size. It is then carried by means of an inclined conveyor to the top of the washery, which consists of three large washers and a 56 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. number of jigs. The amount of coal cleaned at this plant ranges from 250 to 300 tons a day. The large washer consists of a steel chamber in the form of an inverted cone, inside of which are projecting arms and stirring plates revolved by a driving gear above. The water supply enters at the bottom from a perforated pipe. The coal is introduced at the top from a chute and is kept in a continual state of agitation by a current of water. As it is lighter than the impurities, it remains at the top and passes out through the overflow into conveyors, while the water and sludge drain through the hopper into a sludge tank. The impurities sink into a lower chamber of the washer, which is pro- vided with two valves, one above and one below. When this chamber is filled, the upper valve is closed and the lower opened to discharge the refuse. By this process the coal is cleaned rapidly, but the results on the whole are not so satisfactory as those obtained by the jigs. The jig washer consists essentially of a large wooden tank divided into two compartments, one containing a screen on which are placed a number of small pieces of feldspar, the other provided with a piston moved up and down by means of an eccentric, imparting to the water the necessary pulsations. By this means the water is forced up through the screen, lifting the unassorted material and allowing it to settle again, thus affording an opportunity for the products of different specific gravity to adjust themselves according to the law of equally falling particles. The coal remains at the top of the wooden tank, the slate next below, and the pyrite at the bottom. These products of separation are drawn off through gates placed at proper heights in the sides of the jig and are carried away by screw conveyors — the coal to a large bin, where it is allowed to drain; the pyrite to an elevator, where it is rinsed and dropped into railroad cars; and the slate to the waste pile. The water used in the washery is taken to a tank outside the plant, and after the sediments which it contains have settled to the bottom, the clear water is drawn off from the top and pumped back into the washer. The iron-pyrite nodules removed by the above-described process are shipped as a by-product to the large smelters at Great Falls, where they are used as an additional fuel and flux in the blast- furnace charge. By this utilization the pyrite pays for its separation from the coal. Coal from the middle bench of the Belt Creek bed was formerly coked, and 100 ovens having a capacity of 3 tons each were built for this purpose. It was found, however, that the bench of coking coal was too thin to pay for its separation from the other varieties of coal, and consequently the coke ovens are not now used. A view of the Anaconda Copper Mining Company’s plant at Belt is shown in PI. IX. ANACONDA COPPER MINING COMPANY'S COAL PLANT AT BELT, MONT. COAL. 57 Schmauch mine . — The Schmauch mine, situated on the east side of Belt Creek at Belt, nearly opposite the Anaconda Copper Mining Company’s mine, is probably the 'largest of the smaller openings. This mine is worked continuously by a few men, but it has only a small output, which is sold to ranchmen in the vicinity of Belt. The entry extends several hundred feet from the outcrop, but the exact length could not be measured owing to cavings in the mine. The bed lies nearly horizontal, dipping slightly to the north. A represen- tative section shows a thickness of about 6§ feet, consisting of three benches. The lowest is 28 inches thick, containing a bone parting 3^ inches thick 12 J inches above the base. Above this bench is a 4-inch layer of bone, followed by 3 inches of coal, constituting the middle bench. This is overlain by 8 J inches of bone, which is followed in ascending order by a bed of coal 34 inches thick — the top bench (5). The occurrence of a bony layer in the lower bench of coal is unusual in this district. Millard mine . — The Millard mine is situated a few hundred yards south of the Schmauch mine, on the same side of Belt Creek. Here an entry has been driven about 700 feet from the outcrop, with side entries leading to the north and south. The bed is about 6 feet thick, containing partings *which separate the coal into three benches, the lower 28 inches, the middle 6 inches, and the top 30 inches (7). The lowest bench is regarded by the miners as containing the best quality of coal, that of the middle and uppermost benches being of a slightly inferior grade. The Millard mine has a very small output, and most of the coal is sold in the town of Belt. Richardson mine . — On the east side of Belt Creek at Armington is another mine, owned by Matthew Richardson, which is worked during the winter months. The coal here exhibits the usual thick- ness of about 4J feet, including partings. The three characteristic benches are represented— a lower, middle, and upper. The upper- most has a thickness of 1 foot 10 inches, the middle and lowest are 8J and 16 inches thick, respectively. A section of this bed is shown in PL VIII, No. 26. The coal is bright and clean looking, and in composition does not differ materially from the average coal found near Belt. The output of the mine, which is small, is sold in Arm- ington and to ranchmen along Belt Creek valley. Orr mine . — About 1 J miles north of Belt, on the east side of Belt Creek, there is a mining property owned by the Orr Brothers, which is worked to a certain extent, chiefly in the way of development. A main entry has been driven 700 feet from the outcrop, with side entries of considerable length. The coal appears to be of inferior quality and the large amount of material taken out in excavating the entries could not be placed on the market. The coal is dull or lusterless and is not firmly bedded. 58 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. An analysis of an air-dried sample shows about 44 per cent fixed carbon, 21 per cent volatile matter, 28 per cent ash, and a small amount of sulphur. A representative section of the mine shows five benches of coal, with an aggregate thickness of 4 feet 5 inches. The lowest bench is 10 inches thick, followed by 3 inches of bone, which in turn is overlain by 10 inches of coal. Above this coal is a 12-inch layer of bone overlain by 7 inches of coal of a rather inferior variety. Over this coal is 10 inches of bone followed by 22 inches of coal, constituting the uppermost bench of the bed. A comparison of this coal bed with those in the Schmauch and Millard mines indi- cates that partings have developed in both the lower and upper coal benches. ABANDONED MINES. The remaining small mines of the Belt district are the Hill, Buzzo or Hill, Boston and Montana, Herman & Powell, Watson, Brady, and American Smelting and Refining Company. Hill mine . — An abandoned mine, said to be now owned by J. J. Hill, is located on the west side of Belt Creek at Armington. A large entry has been excavated, and, to judge from the size of the dump, considerable coal was taken out. A section of the bed shows 3 feet 2 inches of coal, not including three layers of bony coal which occur near the middle (24). The coal is apparently of good quality, but contains the usual amount of sulphur in the form of iron-pyrite nodules. The uppermost bench is characterized by joint planes run- ning in opposite directions, separating the coal into small cubical blocks. Buzzo or Hill mine . — About one-fourth mile south of the aban- doned Hill mine, on the same side of Belt Creek, there is another opening known as the Buzzo mine, also owned by J. J. Hill. This mine is more or less caved at the mouth of the entry, but the general succession of the members in the coal bed was obtained. Three benches of coal are present, the lowest 14 inches, the middle, which is very impure, 5| inches, and the uppermost 30 inches thick (22). The coal appears to be of good quality in the uppermost bench, but that found in the middle bench is inferior. No analysis was made. The entry is said to be 500 feet long, but as the mine was flooded it was impossible to examine in detail the underground workings. The mine has a sandstone roof and a clay floor. Boston and Montana mine . — The Boston and Montana mine, located about 500 yards south of Orr Brothers’ mine, in the SE. J sec. 23, T. 19 N., R. 6 E., contains a bed of coal similar in many respects to that found in the Orr mine. It has a sandstone roof and shale floor. A graphic section of the bed is given in PI. VIII, No. 2. The three benches have an aggregate thickness of 54 J inches. The lowest con- tains a layer of bone, or bony coal, 12 J inches above the base. This COAL. 59 bench is overlain by 5| inches of bone, which is followed by the mid- dle bench of coal, 3 inches thick. Above the middle bench there is a thin bony parting underlying 28 inches of impure coal, the top bench of the bed. A comparison of the sections at the Orr and at the Boston and Montana mine appears to indicate that the quality of the coal becomes better to the south. Herman Ac Powell mine. — About 300 yards north of the Richard- son mine, on the eastern side of Belt Creek at Armington, there is an abandoned opening known as the Herman & Powell mine. Two entries 75 feet apart have been excavated on the bed. The south entry is 250 feet long, extending in a southeasterly direction, but has no side entries. A section of the coal bed in this entry shows 4 feet of coal separated into three benches, the lowest 18 inches, the middle 11 inches, and the uppermost 19 inches thick (18). The mine has a slate roof and a clay floor. The north entry is 350 feet long and runs in a northeast direction. It has one entry on the southeast, which branches from the main tunnel 75 feet from its mouth. A section of the bed in this entry shows a thickness of 54 \ inches divided into lower, middle, and upper benches, measuring 16J, 11, and 27 inches, respectively. The roof is dark-colored shale and the floor clay. This mine has not been operated for several years, but according to reports considerable coal was formerly taken out. Watson mine. — About one-fourth mile south of the Richardson mine a tributary canyon known as Armington Coulee enters Belt Creek valley. On both sides of this coulee the coal bed is exposed, and several openings have been made. The largest on the south side of the coulee is known as the Watson mine. Here an entry has been excavated for a distance of 160 feet, exposing a bed of coal, including partings, 5 feet 1J inches thick. Of this amount 4 feet 1 inch con- sists of coal, the remainder of dark-colored bony material. Three benches are recognized, the lowest 13 inches thick, the middle 13^ inches, and the uppermost 22^ inches. The middle bench appears to be of an inferior quality, although no analysis has been made. The lower bench contains a large amount of sulphur in the usual form. The bed has a slate roof and shale floor. Brady mine. — On the north side of Armington Coulee, directly oppo- site the Watson mine, there is an abandoned opening known as the Brady mine. The entry at this place extends 150 feet from the out- crop, with one room on either side. The coal bed has a total thick- ness of 55 \ inches. The coal of the lower bench is bright looking, but contains much sulphur in nodular form. The coal in the upper part of the top bench has a dull appearance and is probably of infe- rior grade. American Smelting and Refining Company mine. — On the west side of the main road between Armington and Belt, near the Belt 60 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. cemetery, there is an abandoned entry which was excavated by the American Smelting and Refining Company. This entry is well tim- bered, and the indications are that plans were laid for extensive development. The property is now abandoned, and the entry is caved so that it could not be examined for more than a few feet from the mouth. No information was obtained regarding the quality of the coal. PROSPECTS. Entry prospects . — Considerable prospecting has been carried on in Belt and vicinity. Along Neel Creek, one of the principal tributaries of Belt Creek from the west, coal prospects can be seen at short inter- vals on either side of the canyon. Few of these prospects extend more than a few feet from the outcrop and they appear to have been opened more to determine the thickness of the coal bed than with the intention of developing a mine. One of the largest of these prospects, which may be regarded as a small mine, is owned by E. R. Clingan and is located in sec. 2, T. 18 N., R. 6 E. A section of the bed at this place shows 54 J inches of coal, excluding partings. The three charac- teristic benches are present, the lowest having a thickness of 24 inches, the middle of 7J inches, and the uppermost of 23 inches. Diamond-drill prospects . — In addition to the above prospecting, more or less diamond-drill boring has been done on the high plateau west of Belt Creek, in order to ascertain the thickness of the coal beds in different parts of property owned by large mining companies. No logs of these borings were obtained. SAND COULEE MINES. GENERAL STATEMENT. Three large coal companies are now operating along Sand Coulee and its tributary canyons in the vicinity of Stockett. These are the Cottonwood Coal Company at Stockett, and the Nelson and Gerber coal companies at the town of Sand Coulee. In addition there are a number of prominent individual producers; those deserving especial mention are the Mount Oregon Coal Company and the owners of the Dahn, Brown, and Stainsby mines. This locality was the second to receive attention in the development of the coal resources of the Great Falls field, and at present is the largest producing district of the entire field and one of the largest in the State. Branch railroad lines connect Stockett and Sand Coulee with the Neihart branch of the Great Northern Railway at Gerber station, and a large amount of coal is shipped from these towns to Great Falls and also some to more distant points along the Great Northern main line both to the east and west. The location of the mines is shown on PI. II; sections of the coal beds are shown on PI. X. U. S. GEOLOGICAL SURVEY BULLETIN NO. 356 PL. X 55 Gerber mine 47 54 48 46 57 .59 Dahn’s mine end of north- Gerber mine Gerber mine Gerber mine Stainsby mine Stainsby mine 100'from mouth east entry Room No. 3 Room No. 1 Room No. 1 Room No. 1. east end of main entry of main entry 42" 5 Zz Nelson No. 2 mine 6 +109 =115 10‘/ a "+143V2" = 154" 51 Nelson mine No.l Butt entry off No. 5 south 52" 62 Cottonwood Coal Co., No. 12 Butt off No. 2 south 10 " 6"00j H - 1 ” io " 6"+73"=79" 7"! 36"+30"=66" 16 V2" 10"+ 108"= 118" 7 ,,+ 109V2 " - 1 16 V2 " 61 60 56 Cottonwood Coal Cottonwood Coal Rrnwn mino C0..N0.5 Butt, off Co., Room No. 12 _ ™ No. 2 north off No. 2 south 3 72" 76 Mount Oregon Coal Co.,mine 2V 2 " ' 167 =no l /s' Sarzin mine hear Stockett 2l"+ Prospect 3 miles SW. of Stockett 13" 13" i m. 3" 2" 17" 27" 38" 2 " 17"+ 120"= 137" 6"+90"=96" 6"+91"=97" 18"+ 85"= 103" 3"+ 93"= %" S0V2"+ 78"= I28V2" 66+"+ 84"= 150' Bone Impure or bony coal Clay Thickness of coal shown to right of sections Thickness of waste shown to left of sections Vertical scale, 1 inch=5 feet SECTIONS OF COAL BED IN SAND COULEE DISTRICT, MONTANA. COAL. 61 MINES OPERATED. Cottonwood Coal Company mine . — The mine operated by the Cot- tonwood Coal Company, which is owned by the Great Northern Rail- way, is located at Stockett, where the company has extensive hold- ings. Five mines have been opened since 1898 — Nos. 1, 2, and 3 in 1890; No. 4 in 1900; and No. 5 in 1903. All are in sec. 36, T. 19 N., R. 4 E., mine No. 1 in the eastern part, No. 2 in the SE. \ SE. 1, No. 3 in the NE. \ SW. No. 4 in the NW. 1, and No. 5 in the NW. \ NW. i. This company has carried on extensive mining operations from the opening of the first mine in 1898. At present Nos. 1, 2, 3, and 4 are abandoned. The thickness of the coal bed worked in mine No. 5 (PL XI, A) is from 5 to 10 feet, not including partings. Four benches of coal are present in this mine, the lowest having a thickness of 15 inches, the next higher 73 inches, the third 22 inches, and the fourth and top bench 10 inches. Only the first and .second benches, however, are mined. The bed worked has a bone roof and clay floor. It lies nearly horizontal, dipping slightly to the north. A graphic section showing the thickness of the benches and bone partings is given in PL X, No. 62. The coal con- tains sulphur in characteristic nodular form. The Cottonwood Coal Company’s mine has probably the best- equipped plant in the Great Falls coal field. It is provided with modern appliances for furnishing air, light, and water, both to the plant and to the underground workings. The impurities found in the different benches of the coal bed are sufficient to make it neces- sary to clean the coal before it can be placed on the market, and this is done by a dry process which separates the sulphur nodules and the bone from the coal. The coal is carried from the mine in pit cars of a capacity averaging about 1J tons. After being weighed on an automatic scale it is dumped by a cross-over tipple above a bar screen, with spaces between the bars 2 inches wide. This screen separates out the smaller pieces of coal, which constitute about 30 per cent of the total, allow- ing them to fall on a shaking screen having 1-inch round perforations. The slack passes through the screen and is loaded directly into rail- road cars or taken to the boiler room by means of a wire-rope con- veyor. The coal that passes over the shaking screen slides into a hopper from which it is fed into an elevator that carries it to the top of the building. The coal that passes over the bar screen falls upon a traveling belt 4 feet 6 inches wide and 26 feet long. Men stationed on either side remove from this belt any large pieces of slate or other foreign matter such as machine picks, car couplings, or sprags, and throw them into a rock elevator. The belt is operated by a clutch, so that in case a large quantity of impurities appear it can be thrown out of gear, and all 62 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. the impurities can be removed before the coal goes on. The belt de- livers the coal to rollers, which reduce it to a size not exceeding 4 inches in largest dimension. It is necessary to reduce the coal to this size in order to detect and remove the sulphur balls present. The rollers are of removable-tooth style, 36 inches in diameter, 48 inches wide, and revolve 75 times per minute. From the rollers the coal is elevated by a continuous elevator hav- ing buckets with a capacity of 110 pounds of coal when level full, operated at a speed equivalent to 200 tons per hour. The capacity of the fine-coal elevator is 90 tons per hour, giving a combined elevat- ing capacity of 290 tons per hour, or 2,900 tons per day of ten hours, an amount which, added to the slack separated out by the shaking screen, gives a total capacity of 3,200 tons per day. The coal raised by the elevators is evenly divided over an inclined shaking screen 5 feet wide and 46 feet long, whose plates have 1, 1J-, 2, 2J, and 3 inch round perforations which separate the coal into slack, pea, nut, stove, egg, and broken sizes. The slack resulting from the breakage of the coal is clean, and, not needing any further preparation, it descends through a hopper to the top strand of a conveyor, which carries it directly to the mixed-coal bin. The other sizes are fed by means of other hoppers into spiral separators which separate out the greater part of the impurities by means of centrifugal force and gravity. These impurities pass either to the lower strand of the conveyor, being taken thence to the rock elevator, or from one set of spirals to the bins by means of chutes, which gives an opportunity to repick the refuse by hand and save any coal that may still remain. The refuse is finally loaded into railroad cars and used for the purpose of widening banks along the railroad. The coal from the spirals drops onto two picking bands 4 feet wide and 50 feet long, which convey it to the mixed-coal bin and give an opportunity to pick out by hand any impurities not already removed. From one set of the spirals inclined chutes carry the coal into bins for loading straight sizes, any remaining impurities being removed by hand while the material is on the chutes. On account of the slight difference in specific gravity of coal and hone, the spirals are adjusted so as to retain only the slate and flat sulphur balls, leaving the bone to be removed by hand. The round sulphur balls, which on account of their shape are the first to leave the spirals and go with the coal, also have to be removed by hand. The rock elevator, having continuous buckets 12 by 30 inches in size, elevates the impurities into a bin, from which they are loaded into a 6-ton car and hoisted by a pair of gear-tailed rope engines with 10 by 18 inch cylinders to the top of the adjoining hill and dumped automatically. U. S. GEOLOGICAL SURVEY BULLETIN NO. 356 PL. XI A. COTTONWOOD COAL COMPANY’S MINE NO. 5, NEAR STOCKETT, MONT. B. NELSON COAL MINE AND PLANT AT SAND COULEE. MONT. COAL. 63 The machinery of the entire plant is driven by a double engine with 13 by 18 inch cylinders, running 150 revolutions per minute. The percentage of refuse in the various sizes after being treated in the above-described process is stated below: Refuse remaining in coal at Cottonwood Coal Company’ s mine , Stoclcett, Mont. Per cent. Pea 4 Nut 3 Stove 3 Egg 2 Broken 1 Mixed 2. 5 Of 2,000 tons of mine product daily dumped into the breakers, 200 tons of the various impurities are removed, and these impurities do not contain on an average over 1 per cent of coal. For greater detail concerning the breaker used at this plant, including diagrams, the reader is referred to a report by Lewis Stockett,® of Stockett. Nelson mines . — The Nelson mines, the oldest operated in the Sand Coulee basin, are located at the town of Sand Coulee (PI. XI, B). There are two mines; No. 1 is situated on the east side of Sand Coulee, and No. 2 is on the west side, a short distance below the town. Mine No. 2 was first opened by Charles Locery in 1905 and was later sold to the Nelson-Jenks Coal Company. It is not being worked at the present time. Mine No. 1 was extensively worked by the Cotton- wood Coal Company before that concern moved to its present loca- tion at Stockett. Operations were begun by the Nelson Coal Com- pany at this mine in 1903, and since then the property has been worked continuously. The main entry has been driven in an easterly direction to a distance of about 3,000 feet from the outcrop, and the total acreage of the underground workings is considerable. The coal- bearing rocks at this mine are locally disturbed, the miners having encountered numerous rolls; and in places the coal is entirely absent. The bed ranges in thickness from 6 to 9 feet. It lies nearly level? with a general but low dip to the north, and is composed of benches like those worked at the Gerber mine, described below. The lower bench has a thickness of about 1 foot 6 inches and the upper of about 7 feet 6 inches (50). Between the two is a layer of dark-colored bone 6 to 10 inches thick. The coal of both benches is clear, firm, and noticeably free from foreign material. The sulphur is present in the usual form, but is not abundant. A layer of dark-colored shale 8 inches thick forms the roof. It is overlain by another bench of coal which is not mined at present. The floor consists of dark-colored shale. Stockett, Lewis, A bitum.nous coal breaker in Montana: Min. World, vol. 20, March 20, 1904. 64 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. The company employs about 175 men, who work continuously, and in general the plant is very well equipped for handling coal. Ventila- tion is furnished by a 12-foot fan, and the water is taken out by three large pumps. The coal is machine mined, by the pillar and block system, and is cleaned and assorted into different sizes by means of a 20-foot picking table and a 44-foot shaking screen. Horse haulage is employed. Gerber mine . — One of the three large mines in the Sand Coulee dis- trict is owned by the Rock Springs or Gerber Coal Mining Company. It is located on the west side of Straight Coulee, a tributary to Sand Coulee, about half a mile south of the town of Sand Coulee, in the NE. \ sec. 23, T. 19 N., R. 4 E. The mine was opened in 1890 and has been worked continuously since that time. A large force of men is employed and the underground workings are extensive. Though slight local dips are more or less common, the coal bed lies nearly level, dipping only slightly to the north. It is from 6 to 9 feet thick, including partings. It is believed that the coal worked comprises the lower part of the coal bed as exposed in certain parts of this mine and at other places in the Sand Coulee district. Two benches are present — a lower, which has a thickness of about 2 feet, overlain by 2 to 6 inches of dark-colored bone, followed by an upper bench 4 to 7 feet thick (46, 47, 48). Above the upper bench worked there is in some places a coal bed 38 inches thick (55). The coal of all benches is firm, clean-looking, and noticeably free from bony partings. Sul- phur, in characteristic nodular form, is present in considerable abun- dance. The roof consists of a strong dark-colored shale and the floor is a firm, compact clay. A few rolls occur at different places in the bed, but in general it is not much disturbed. The Gerber Mining Company has a well-equipped plant, with the usual modern appliances for handling coal. There is considerable water in the mine, a portion of which is taken by steam pumps to a reservoir outside the mine, the remainder being pumped to a large tank on the hillside, from which the boilers are supplied. The tipple is located about 600 feet from the mouth of the mine at the end of the railroad. The coal is all machine mined, the bed being worked by the room and pillar system. The coal is fairly free from impurities, and such as exist are taken out by hand picking in the mine and screening at the tipple, no elaborate process being employed. The haulage is effected by means of horses and a small donkey engine. A 12-foot fan furnishes sufficient air to keep the mine well ventilated. Most of the output is shipped to points north, east, and west, local sales being small. Mount Oregon Coal Company mine . — The Mount Oregon Coal Com- pany mine, which is the largest of the smaller mines in the Sand Coulee district, is located near the town of Sand Coulee in the SE. \ sec. 14, COAL. 65 T. 19 N., R. 4 E. This mine is at present worked by Thomas Mokko, and was opened in the spring of 1902. The bed worked has a thickness of about 8 feet. It consists of two benches, a lower bench 30 inches thick, overlain by 3 inches of clay, followed by 63 inches of coal, constituting the upper bench (76). The main entry extends several hundred feet from the outcrop, with numerous side entries. In working the bed the room and pillar system is carried out. Sufficient provision has been made for the proper ventilation of the underground workings and the water is taken out by a gravity system. The haulage is effected by horses, and a coal bin of 20 tons' capacity is located at the mouth of the mine. The impurities are removed by hand picking and screening. The company employs 18 men and has a daily output of about 45 tons. Dahn mine . — The Dahn mine, located at Sand Coulee, in the north- east corner of sec. 13, T. 19 N., R. 4 E., is another of the smaller mines of this district. It was first opened in 1890, and has been worked intermittently up to the present time, changing hands several times in the interval. The coal bed underlies a hill covering about 20 acres. Most of the coal in this hill has been worked out. At present the output is 10 to 15 tons a day and only a few men are employed, but prior to 1903 the mine was operated in a more extensive way, 40 to 50 men being employed, with an output of about 100 tons a day. The coal is between 13 and 14 feet thick. Three benches are present; the lowest is 3 feet thick, the middle 7 feet, and the upper- most 3 feet 2 inches. Between the lowest and the middle bench there is a 2^-inch layer of bone, and above the middle bench a 10-inch layer of shale (54). Only the lowest and middle benches are worked in the Dahn mine. The mine has a shale roof and floor. Brown mine . — A small coal opening owned and operated by William Brown is located in the SW. f SW. } sec. 18, T. 19 N., R. 5 E. The main entry extends about 500 feet from the outcrop, with two small entries on either side. The mine has been worked for only about two years. Although the beds are nearly horizontal, they are consider- ably broken and disturbed, making progress slow. The coal is about 7 feet thick, divided into three distinct benches, the lowest 3 inches, the middle 10 inches, and the uppermost 6 feet (56). Shale forms the roof and floor. The output is very small, and operations are carried on only during the wunter months. Stainsby mine . — On the west side of Cottonwood Coulee, about 2 miles belovr Stockett, near the center of sec. 19, T. 19 N., R. 5 E., is a small mine owned by William Stainsby. Two men are employed, and a small amount of coal is taken out. The bed has a thickness of 12 feet, not including partings, which are about 22 inches thick. There are four benches of coal in all — the lowest 1 foot 5 inches thick, 54937 — Bull. 356—09 5 66 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. the next higher 5 feet, the next above that 2 feet 2 indies, and the top bench 3 feet 6 inches (59). The coals of the different benches do not appear to vary materially in quality, except that the top bench con- tains an unusually large amount of sulphur in the characteristic nodular form. ABANDONED MINES. In addition to the above-described mines there are in the Sand Coulee district three abandoned openings, known as the Mitchell, McKinsey, and Sarzin mines (PI. X, 63). These are all small and of minor importance. A number of diamond-drill prospect holes have been sunk by some of the larger coal companies holding property in the immediate vicinity. SMITH RIVER MINES. GENERAL STATEMENT. In the bluffs bordering Smith River and its tributaries, Hound Creek and Ming Coulee, the coal -bearing zone is exposed at many places. Coal has been mined intermittently throughout this district for more than twenty-five years, and within the last decade consider- able prospecting has been done in order to ascertain the extent of the bed. Several small mines are now operated, and there are a few abandoned mines from which coal is occasionally taken. Those worked are the Carville, Gibson, Patterson, Bickett, and Love mines, which have a combined annual output of only a few hundred tons. The locations of the prospects and mines are shown on PI. II; sections of the coal beds are shown on PI. VIII. MINES OPERATED. Carville mine . — The Carville mine, situated on the west side of Hound Creek, in the SW. J SE. \ sec. 24, T. 17 N., R. 2 E., is one of the largest in the Smith River district. Coal has been taken out at this place for about seven years. The main entry extends 375 feet west from the outcrop, with a side entry to the south 75 feet long and 40 feet wide, branching from the main entry 90 feet from its mouth. On the north side of the main entry there is another side entry with four large rooms. This mine is not operated in an extensive way, but it is worked continuously, the total annual output being about 1,800 tons. It supplies coal to ranchmen throughout a considerable territory to the south and west. The bed mined is 5 feet 6 inches thick with no appreciable partings. The lower 6 inches of coal is dull looking and in places bony, but it is firm and as a fuel gives good satisfaction. Above this bed there is a bright coal said to be suitable for blacksmithing, which contains numerous iron-pyrite nodules. The thickness and character of the bed remain relatively uniform COAL. 67 throughout the workings. The rocks at this place dip slightly to the north and west and are little disturbed. Gibson mine . — The Gibson mine is located in the extreme south- east corner of sec. 24, T. 17 N., R. 2 E., on the east side of Hound Creek, opposite the Carville mine. It is operated only during the fall and early winter months, and the annual output is about 1,200 tons. The bed worked is slightly thicker than that exposed in the Carville mine, measuring 5 feet 10 inches (69). The upper 2 feet is a bright, firm-looking coal. Beneath this member is a dull bony coal 10 inches thick, followed by 46 inches of dull-looking coal which is said to burn well and as a domestic fuel is in general satisfactory. The main entry extends for about 300 feet at right angles to the face of the bluff. It has two large rooms on the north and one side entry on the south extending diagonally from the main entry to a distance of about 430 feet. This entry is cut across by another side entry, which leaves the main entry at right angles near the back end. The rocks lie nearly horizontal, dipping slightly to the northwest, and are not badly disturbed. The mine is worked by the room and pillar system and little difficulty is experienced with water. Patterson and Rice mines . — The Patterson mine is situated high in the blutfs on the east side of Smith River, a short distance above the mouth of Hound Creek. The first opening was made in 1903, and the main entry now extends to a distance of 150 feet. A short dis- tance to the east is located the Rice mine, from which, it is said, coal was taken nearly twenty-five years ago. The bed mined has a total thickness of 4 feet 10 inches (78) and the coal appears to be of good quality. Biclcett mine . — On the north side of Ming Coulee, about 1J miles above the Eden creamery, a small tonnage of coal is extracted from the Bickett mine. The coal zone or bed is about 18 feet thick and dips at a small angle to the northwest. The upper 10 feet does not contain workable coal, but below this there are two benches of about equal thickness, separated by 8 inches of bone (66). Freshly ex- posed surfaces of both benches exhibit bright, firm coal. The base of the lower bench, however, contains considerable sulphur in nodu- lar form. The floor and roof of the mine are composed of clay and shale, respectively. Love mine . — The Love mine consists of a small opening in the bluffs on the south side of Ming Coulee about one-half mile above the Eden creamery, in the E. \ SE. J sec. 31, T. 18 N., R. 4 E. It has been worked in a desultory way for the last ten years, but only a small amount of coal has been taken out and the mine is poorly developed. The coal bed is unusually thick at this place, measuring over 8 feet, and though the rocks are more or less broken at the sur- face, it is believed that an entry driven some distance into the hill 68 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. would encounter the coal undisturbed. The coal zone shows the usual variation, both in number and thickness of coal beds. Four different benches were recognized, of which only the first and second, counting from the base, are mined. The lowest bench is 14 inches thick. It is underlain by bone containing thin streaks of coal and resting on clay. Above the lowest bench of coal there is 1J feet of bone, followed by 3 feet of coal constituting the upper bench mined. This coal is overlain by 8 inches of bone, forming the roof of the mine. Above the roof there are two coal benches, the lower 18 inches and the upper 3 feet thick; they are separated by 10 inches of bone (65). PROSPECTS. In addition to the above-described mines the Smith River district contains a number of prospects, some of which exhibit coal of work- able thickness. One opening of this character, owned by Mr. Hoag, is located in the northwest corner of sec. 31, T. 17 N., R. 3 E., and there are others in this immediate vicinity. The location of prospects and mines in this part of the Sand Coulee basin is shown on PI. II. OTTER CREEK AREA. LOCATION AND EXTENT. The Otter Creek area, which is located southwest of Geyser, ex- tending along Otter Creek for a distance of about 1 0 miles, lies mainly in T. 17 N., Rs. 8 and 9 E., and includes a small portion of T. 16 N., R. 9 E. The southern limits of the area are definitely marked by the outcrop of the coal, along which a sufficient number of prospect pits occur to indicate its workable character; but to the east, north, and west the extent of the coal can onl} r be inferred from a study of a comparatively small number of exposures. To the east the last exposure of coal of workable thickness is found on the east side of Avoca Creek, at the Chamber Brothers mine. A quarter of a mile farther east, in a small tributary of Avoca Creek, the Meredith pros- pect shows that the coal of this horizon is not only of less than a workable thickness, but also of inferior quality. Still farther east, in another tributary of Avoca Creek, 1J miles distant , prospects show that only a few inches of coaly shale occur at the coal horizon. From these prospects and natural exposures of the coal to the east it is assumed that the eastern limit of the Otter Creek area must lie some- where between the Chamber Brothers mine and the Meredith prospect. Nor can the northern extension of workable coal be more than approximately located. As previously stated, the coal-bearing rocks of this general vicinity dip gently northeast, passing beneath the overlying Colorado shale, and exposures are therefore few. At the mouth of Williams Creek, however, that stream has cut sufficiently COAL. 69 deep to expose the coal bed, which is not of workable thickness. Northwest of this place, on either side of Otter Creek, where the coal is poorly exposed, the bed consists of only a few inches of coaly shale containing thin streaks of coal. On the east side of a small tributary of Little Otter Creek, about 2 miles south of Mann, there are two prospects which demonstrate that the coal horizon shows mainly impure coaly shale. From this evidence it seems highly probable that coal of workable thickness does not continue beyond a line extending northeastward from the coal exposures on the ridge between the Chamber Brothers mine and the Meredith prospect nearly to the mouth of Williams Creek, thence westward along the south side of Otter Creek nearly to Little Otter Creek, thence south- ward to the vicinity of the Nullinger mine. The limits of the area are shown in PI. II ; sections of the coal beds are shown on PI. XII. CHARACTER AND THICKNESS OF COAL BED. The Otter Creek area is underlain by one bed of coal which ranges in thickness, as indicated by exposures, from 3 to 6 feet; the maxi- mum thickness, however, in the center of the basin probably exceeds 6 feet. The coal generally occurs in two benches, although at one mine three distinct benches were observed. The maximum thick- ness of workable coal is 4 feet, as shown by the section at the Nollar mine, where it occurs in one bed with no partings. At other places, wherever two benches are present, the lower is generally the thicker and contains the better coal. The parting between the two benches is commonly bone. At the mine where three benches occur their total thickness is 2 feet 3 inches. It is difficult to give an average section of the coal bed in the Otter Creek area, for only one mine has been opened which may be regarded as representative of the coal in the central part. This mine, owned by Mr. Nollar, shows a total thickness of 4 feet, as above stated. It is probable that over a considerable area the coal retains this thick- ness, possibh r increasing somewhat, but throughout the marginal portions it doubtless becomes thinner. DEVELOPMENT. GENERAL STATEMENT. The coals of the Otter Creek area have not been mined to any con- siderable extent. Though coal has been taken out of different open- ings for a number of years, the area as a whole is practically unde- veloped. The Billings and Northern Railroad now being constructed will pass near the northern limit of the field, thus affording transpor- tation facilities. At the present time only three small mines are worked — the Nollar, Nullinger, and Chambers mines. Of these only 70 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. the Nollar is of sufficient size to be regarded as a factor in the pro- duction of coal. The locations of mines and prospects in the Otter Creek area are shown on PL II ; sections of the coal bed are shown in PL XII. MINES OPERATED. Nollar mine . — The Nollar mine is situated at the base of the bluffs on the west side of Otter Creek in the NW. \ sec. 29, T. 17 N., R. 9 E. The mine was first opened in 1902 and during the four years of its operation the total output has not exceeded 300 tons. It is not worked continuously, but a few tons of coal are kept on hand to sup- ply a small local trade. The coal occurs in what is apparently one bench 4 feet thick (79), in which no partings of appreciable thick- ness were observed. The coal is bright and firm, and on close examina- tion shows fine banding on the surface. It contains the characteristic sulphur nodules found in other portions of the field. The entry ex- tends 275 feet from the outcrop in a southwesterly direction. The direction of the main entry at this place is not at right angles to the dip, which here is about due north, but at a slightly greater angle in order to make the entry gradually rise, thus obtaining better drainage. Two side entries extend at right angles from the main entry, one about 80 feet and the other about 200 feet from the face. Each is 75 feet long and is provided with rooms parallel to the main entiy. Opposite the first entry to the south there is a front entry leading northward from the main entry; this is provided with a large room nearly 50 feet long. From the end of the second entry to the south there is a narrow cross entry, which extends parallel to the main entry, past the south end of the first entr}" to the south and thence to the surface. Chamber Brothers' mine . — Coal is taken during the winter months from the Chamber Brothers’ mine, which is located in the NE. I of sec. 4, T. 16 N., R. 9 E., on the east side of West Fork of Avoca Creek. This mine was opened in 1903 and at present has an entry which ex- tends nearly due east for about 125 feet from the face. The coal, which is 2 feet 2 inches thick, is separated into two benches, the lower 14 inches and the upper 12 inches thick. Between the lower and upper benches is a 4J-inch bed of coaly material. Above the upper bench there is 17 inches of light bluish-gray clay, forming the roof, overlain by dark shale which contains thin streaks of coal. This member is followed by a gray massive sandstone. The floor of the mine consists of dark-colored clay. A complete section is given in PL XII, No. 30. Nullinger mine . — The Nullinger coal mine, situated on the east side of a small tributary of Little Otter Creek, in the SE. 1 sec. 21, T. 17 N., R. 8 E., is also a very small mine, at the present time furnishing coal U. S. GEOLOGICAL SURVEY BULLETIN NO. 356 PL. XII 27 74 Larson mine Nullinger mine near Spion Kop i Yz OTTER CREEK AREA 31 33 79 28 Prospect%mile south- Meredith mine Nollar mine Fisher mine east of Meredith mine southwest of Geyser southwest of Geyser on Williams Cr. 48" l 1 /2 ,, +36 , = 37 Vs" 21"+ 30"= 51'' , fH 12" 15"+ 43"= 58" 0"+48"=48" 64 V2"+0"= 64 Vs" Chamber Bros! mine Prospect y 2 mile we; of Larson mine south of Geyser 12 " 1V2 pgfpSj 14"+ 26"= 40" I i6y 2 " 1 "+ 2OV2" = 21V2 " Seman mine Hr" 34 Hughes mine SAGE CREEK AREA 42 Fisher mine 43 41 Prospect 1 mile north- Prospect on east Prospect on east 16" 2"Sm3" "+ 43"= 73'' 45 Sage Creek near Willow Creek west of Fisher mine side of Barnes Coulee side of Barnes Coulee Schultz mine Sheep Co. mine ! 22 " 9" 6 " 12 " 22"+49"=7l" 12 " i2 "|gg 1 9 Vs" 15"+ 30V2"=45V^" 5 4y 2 " 48"+ 15"= 63" 18"+52V2"=70y2" 11 10" J 77 y 2 "+ 20 "= 97 V 2 " Impure or bony coal Shale with lenses of coal Clay Thickness of coal shown to right of sections Thickness of waste shown to left of sections Vertical scale, 1 inch=5 feet SECTIONS OF COAL BED IN OTTER CREEK AND SAGE CREEK AREAS MONTANA. COAL. 71 for only a few ranches near by. The coal bed has a thickness of 3 feet, and is separated by a 1^-inch layer of bone into two benches (74). It is a bright and firm-looking coal, which doubtless warrants more extensive development. The entry has a pitch of about 60° and ex- tends for about 100 feet from the face in a northeasterly direction, at considerably less than a right angle to the direction of the dip, which is here nearly north. ABANDONED MINES. There are three small abandoned mines in the Otter Creek area, two at the mouth of Williams Creek. The one on the south side of the creek is known as the Larson. On it several openings have been made. The opening nearest the road, from which a sample was taken, has an entry 50 feet long. Here the total thickness of the coal is 28 inches, with an appreciable amount of foreign material. About 200 feet east of tins opening there is another mine which is said to extend 150 feet into the hill. This was flooded, rendering it impossible to examine the underground workings. About 150 feet still farther east and at a slightly higher level there is another opening with an entry 135 feet long. In excavating this entry a dike of intrusive material at 60 feet from the surface, trending south-southwest, was encountered, and the remainder of the entry was excavated along one side of this dike. The coal in this entry is about 2 \ feet thick and is overlain and underlain by compact gray shale. A graphic representation of the section is given in PI. XII, No. 27. About 500 feet farther east on the same side of Williams Creek another small opening exhibits a coal bed similar to the one just de- scribed. North of Williams Creek, at the mouth, is the Fisher mine, in which the coal is 22 inches thick. The bed is overlain by 15 inches of bone, followed by 6 inches of coaly shale, above which 15 feet of massive gray sandstone is exposed. A graphic representation of this bed is given in PI. XII, Xo. 28; No. 29 represents an exposure of the same bed in a railroad cut one-half mile farther west. SAGE CREEK AREA. LOCATION AND EXTENT. The Sage Creek area, situated in the eastern part of the Great Falls coal field, a few miles south of Stanford, in the vicinity of Skull Butte, lies mainly in Tps. 15 and 16 N., Rs. 11 and 12 E., but embraces small portions of Tps. 15 and 16 N., R. 13 E. The area described encircles Skull Butte, where the dome-shaped uplift exposes rocks older than the coal-bearing measures. This area ranks second in the field in point of size, being slightly larger than the Otter Creek area and considerably smaller than Sand Coulee area. The southern 72 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. limit of the Sage Creek coal area is definitely marked in most places by the outcrop of the coal, but to the north and to a certain extent to the east and west, the limits of the workable coal must be inferred from geologic evidence. In Barnes Coulee, a tributary of Spring Draw, which is the easternmost locality at which the coal is exposed within the area investigated, the coal bed thins from more than 7 feet on the west side of the coulee to less than 3 feet on the east side, in a distance of less than half a mile. The relative percentages of shale and coal change rapidly in this distance, the former predom- inating on the east side of the coulee. This rapid change toward the east in both the thickness and the quality of the coal in Barnes Coulee, together with the apparent absence of workable coals for several miles farther east, is regarded as sufficient evidence for placing the eastern limit of the Sage Creek coal area not far beyond this coulee. To the northeast, farther down Sage Creek valley, where the coals are covered by an increasing thickness of overlying rocks, a number of diamond-drill prospect holes have been bored in order to ascertain the thickness of the coal in this direction. The results of these drill- ings have not been made public, but in some localities the drilling has been followed by shafting, which indicates that a bed of workable thickness was found. The northern border of this area is arbitrarily placed a short distance beyond the Billings and Northern Railroad from the eastern limit of the district to Stanford, thence westward nearly to Surprise Creek, and thence southwest ward to the coal outcrop in the vicinity of Hazlett Creek. On Hazlett Creek, near the western edge of the area, the coal has been prospected at a number of places. Here the bed is barely of workable thickness and is very shaly. About 3 or 4 miles farther north, on small tributaries of Surprise Creek, the coal bed is repre- sented by only a few inches of impure coal, associated with coaly shale. The same is true on Dry and Shannon creeks, farther west. From the above considerations it seems probable that the western limit of the area underlain by workable coals in the Sage Creek basin lies somewhere between Hazlett and Surprise creeks. The extent of the Sage Creek area and the location of the mines and prospects are shown on PI. II; sections of the beds are shown in PI. XII. CHARACTER AND THICKNESS OF COAL BED. So far as known there is only one coal bed in this area. Its thick- ness, including partings, ranges from 6 to 18 feet. Within this thickness of beds, deposited under coal-forming conditions, the aggre- gate of the coal ranges from 2 \ to 7 feet. The coal usually occurs in the form of three distinct benches, which are generally recognized by miners in the district. The lowest bench is about 2 feet thick and is regarded as the best. Above this is commonly a 2 to 6 inch COAL. 73 parting, overlain by a middle bench 12 to 16 inches thick. Next is generally 1 to 6 inches of bone, followed by the uppermost bench of coal, which ranges from 1 to 2 feet in thickness. The coal is usually covered by 1 or 2 feet of dark-colored shale, which forms the roof of the mine. Above the shale there are in many places impure coaly layers interbedded with brown and black sandy leaf-bearing shale having a thickness of several feet. The next member in ascending order is a gray massive sandstone ranging in thickness from 20 to 60 feet. In the outer portion of the area the base of this sandstone locally forms the roof of the mine. DEVELOPMENT. GENERAL STATEMENT. The coals of the Sage Creek area have not been extensively worked. Coal has been mined in this vicinity for many years, but owing to the lack of transportation facilities the output has never exceeded the amount necessary to supply a small local demand. At the present time mining is carried on at only three small mines, owned by Messrs. Schultz, Seman, and Hughes. The annual output of the Schultz mine is about 1,000 tons; that of the Seman is somewhat smaller. Neither of these mines is well improved. The Hughes mine has only recently been opened. MINES OPERATED. Schultz mine . — The Schultz mine, the largest of the three mines now operated in this district, is located in the SE. I SE. I sec. 20, T. 15 N., R. 12 E., on the west side of Spring Draw, a small tributary of Sage Creek. It was opened in 1894, and, according to the best information obtainable, though operations have been continuous, the output of the mine has never been large. The present annual production amounts to 1,000 tons, which is consumed by ranchmen and inhabitants of small towns within a radius of 10 to 15 miles. The coal zone has an aggregate thickness of slightly over 12 feet, but only the coal of the lower half is mined, none of that in the upper part being regarded as of sufficient thickness to be worked. The coal of the lower part occurs in three benches, which have a total thickness of 4 feet 4^ inches, not including the 6-inch layer of bone 1 foot below the top and the 1 foot of bony coal 2 feet above the base. The lowest bench is 2 feet thick and constitutes the most important coal of the mine. It is black, with a dull luster, and contains more or less pvrite in nodular form. The middle bench has a thickness of about 16^ inches and generally has a bright luster. It, too, con- tains some pvrite nodules. The uppermost bench is about 12 inches thick and is generally more or less free from sulphur (38). Immedi- ately overlying this bench in the upper part of the zone is a layer of 74 GEOLOGY OF GREAT FALLS COAL FIELD, MONTANA. bone 2 feet thick, which forms the roof of the mine. This is followed by 12 inches of dark sandy shale containing thin beds of coal, which in turn is overlain by 21 inches of coal containing a small percentage of bone. Above this coal there is an 8-inch layer of light-colored sandstone, followed by 6 inches of dark coaly shale which immediately underlies massive gray sandstone several feet in thickness. Seman mine . — The Seman mine is located in the SW. \ SE. \ sec. 20, T. 15 N., R. 12 E., a few hundred yards west of the Schultz mine and on the same side of Spring Draw. It is considerably smaller than the Schultz mine and is worked only during the winter months, having a very small output, which rarely exceeds 150 tons a season. Coal has been taken out of this opening for the last decade, but little attention has been given to the proper development of the under- ground workings. The coal bed mined here is almost identical with that worked at the Schultz mine, except in the uppermost bench, which appears to be somewhat thicker. Three benches occur; the lowest bench has a thickness of 2 feet and is overlain by 9 inches of bony coal. Above this is the middle bench, which has a thickness of 16 inches and is followed by a 7-inch layer of bone. Next is 15 inches of bright, firm-looking coal, which constitutes the uppermost bench. A com- plete section is shown in PI. XII, No. 36. The deposit has the characteristic shale roof and clay floor exhibited in the Schultz mine. In physical properties the coals of the different benches closely resemble those of the Schultz mine. The characteristic sulphur balls are present, especially in the lowest bench; the middle bench has the usual bright luster, and in practical use these two coals seem to give equal satisfaction. The main entry extends about 400 feet from the face in a meandering but westerly direction. About 200 feet from the mouth of this entry a side entry extends at right angles, approximately 30 feet to the south. Hughes mine . — In 1904 a small mine was opened on the Hughes ranch, on the east side of Willow Creek, in the NE. I sec. 19, T. 15 N., R. 12 E. This mine is about 2 miles northwest of the Schultz and Seman mines, near the southern limit of the Sage Creek area. The total thickness of the bed worked is 5 feet 8 inches, including a 9-inch layer of bony coal 16 inches above the base and excluding a 3-inch bed of true bone 2 feet below the top of the bed. Coal occurs in three benches, as is common in other parts of the area. The lowest bench is slightly thinner than usual, being only about 16 inches thick. This is due to a 2-inch layer of clay that occurs at the base of the bench and separates it from a 3-inch bed of coal not mined at this place. The middle bench is 16 inches thick and is bright and firm, but contains a few thin layers of bone. A 3-foot bed of good-looking coal constitutes the uppermost bench. It is overlain by dark-colored COAL. 75 sandy shale, which forms the roof. A graphic section of the bed is given in PL XII, No. 34. ABANDONED MINES. In addition to the above-described mines, there are in the Sage Creek area four abandoned mines from which considerable coal has been taken during the last ten years. These are the Corwin & McGregor (now owned by Mr. Schultz), the Fisher, the West Fork of Willow Creek, and the Sage Creek Sheep Company* mines. Graphic sections of all except the Corwin & McGregor mine are given in PL XII, Nos. 42, 43, and 45. Corwin