s 14.GS: RP.I 188 IttlNOfS GEOLOGICAL SURVfY HBPAPY :. J STATE OF ILLINOIS WILLIAM G. STRATTON, Governor DEPARTMENT OP REGISTRATION AND EDUCATION VERA M. BINKS, Director DIVISION OP THE STATE GEOLOGICAL SURVEY JOHN C. FRYE, Chief URBANA REPORT OF INVESTIGATIONS 188 SANDSTONE RESOURCES OF EXTREME SOUTHERN ILLINOIS A Preliminary Report BY D. L. BIGGS and J. E. LAMAR PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1955 STATE OF ILLINOIS WILLIAM G. STRATTON, Governor DEPARTMENT OF REGISTRATION AND EDUCATION VERA M. BINKS, Director DIVISION OF THE STATE GEOLOGICAL SURVEY JOHN C. FRYE, Chief URBANA REPORT OF INVESTIGATIONS l! SANDSTONE RESOURCES OF EXTREME SOUTHERN ILLINOIS A Preliminary Report D. L. BIGGS and J. E. LAMAR PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 19 5 5 ORGANIZATION STATE OF ILLINOIS HON. WILLIAM G. STRATTON, Governor DEPARTMENT OF REGISTRATION AND EDUCATION HON. VERA M. BINKS, Director BOARD OF NATURAL RESOURCES AND CONSERVATION HON. VERA M. BINKS, Chairman W. H. NEWHOUSE, Ph.D., Geology ROGER ADAMS, Ph.D., D.Sc, Chemistry ROBERT H. ANDERSON, B.S., Engineering A. E. EMERSON, Ph.D., Biology LEWIS H. TIFFANY, Ph.D., Pd.D., Forestry W. L. EVERITT, E.E., Ph.D. Representing the President of the University of Illinois DELYTE W. MORRIS, Ph.D. President of Southern Illinois University GEOLOGICAL SURVEY DIVISION JOHN C. FRYE, Ph.D., D.Sc, Chief (24267—2400—9-55) CONTENTS Page Sandstone formations 5 Geologic reports 5 Nature of sandstone exposures 6 Workability of deposits 6 Testing of deposits 7 Samples 7 Deposits sampled 7 Laboratory preparation of samples 10 Disaggregation of sandstone 10 Mineral composition 10 Grain shape 1 3 Sieve tests 13 Chemical analyses 13 Uses of sandstone 19 Possible uses of sands sampled 20 ILLUSTRATIONS Figure Page 1. Areas covered by geologic reports 6 2. Locations of sandstone outcrops sampled 8 Plate 1. Photographs of Bethel and Casey ville sand grains 11 2. Photographs of Caseyville and Tradewater sand grains 12 TABLES Page 1. Thickness and general character of sandstones 7 2. Heavy minerals in sands 10 3. Grain shape of sands 13 4. Results of sieve tests 14 5. Analyses of crude sands 18 6. Analyses of washed sands 19 Analyses of washed, acid- and magnet-treated sands 20 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/sandstoneresourc188bigg SANDSTONE RESOURCES OF EXTREME SOUTHERN ILLINOIS A Preliminary Report BY D. L. BIGGS and J. E. LAMAR ABSTRACT Sandstones crop out at many places in extreme southern Illinois. Most of them are light yellow, buff, or brown. Sixty-five samples from 30 outcrops representing 11 geo- logical formations were investigated. Sieve tests revealed that the sands range from fine to coarse grained. The shape of the sand grains varied from angular to subrounded. Chemical analyses of 14 selected samples in the disaggregated, but otherwise unprocessed, state revealed that 11 samples contain more than 95 percent silica; iron oxide ranged from .18 to 4.2 percent. Washing the samples and eliminating the material passing a 270-mesh sieve increased the silica content of 11 samples to above 98 percent and in most cases lowered the iron-oxide content. Washing, acid treatment, and removal of magnetic particles decreased the iron-oxide content of five samples to below .035 percent. The results suggest that, if properly processed, some southern Illinois sandstones may yield silica sand possibly suitable for a variety of industrial uses. However, test drilling of deposits and testing of resulting samples, together with an evaluation of production costs and available markets, is necessary to demonstrate the uniformity, commercial work- ability, and economic importance of the deposits. Numerous outcrops of several sand- stone formations having a thickness of 50 feet or more are found in that part of Illinois south of the coal fields. Only limited use is now being made of these sandstones — for small tonnages of building stone. This preliminary investigation was undertaken to determine possible uses for the sandstone in the nonstructural field. The assistance of John R. Dyni in the field and laboratory work is gratefully ac- knowledged. Thanks are due also to Jua- nita Witters and L. D. McVicker of the Illinois Geological Survey's Geochemistry Section who made the spectrographic and chemical analyses. SANDSTONE FORMATIONS The geologic "formations" of southern Illinois that are wholly or in part composed of sandstone are listed and underlined be- low, from youngest to oldest. Limestone and shale formations between the sandstones also are named but not underlined. Tradewater Caseyville Kinkaid Degonia Clore Palestine Menard Waltersburg Vienna Tar Springs Glen Dean Hardinsburg Golconda Cypress Paint Creek Bethel Renault Aux Vases The Tradewater and Caseyville sand- stones are Pennsylvanian ; the other forma- mations are Upper Mississippian. The Thebes sandstone, which was sampled in Alexander County, is much older than any of those listed. GEOLOGIC REPORTS Much of the area covered has been mapped geologically and published reports are available. Figure 1 shows the area cov- ered by the various reports further identi- [5] ILLINOIS STATE GEOLOGICAL SURVEY Fig. 1. — Areas covered by geologic reports of the Illinois State Geological Survey. A. Report of Investigations 59. Pre- liminary geological maps of the pre-Penn- sylvanian formations in part of south- western Illinois — Waterloo, Kimmswick, New Athens, Crystal City, Renault, Baldwin, Chester, and Campbell Hill quadrangles: Stuart Weller and J. M. Weller; Explanation and stratigraphic summary: J. M. Weller. 1939. 15 p., 3 pis., 2 figs. 25c. B. Report of Investigations 70. Pre- liminary geologic map of parts of the Alto Pass, Jonesboro, and Thebes quadrangles in Union, Alexander, and Jackson counties: J. M. Weller and G. E. Ekblaw; Explana- tion and stratigraphic summary: J. M. Weller. 1940. 26 p., 1 pi., 2 figs. 25c. C. Bulletin 48. Geology and mineral resources of the Carbondale quadrangle: J. E. Lamar. 1925. 172 p., 5 pis., 28 figs. 50c. D. Report of Investigations 60. Pre- liminary geologic map of the Mississippian formations in the Dongola, Vienna, and Brownfield quadrangles: Stuart Weller and F. Krey; Explanation and stratigraphic summary: J. M. Weller. 1939. 11 p., 1 pi., 1 fig. 25c. E. Bulletin 76. Geology of the fluor- spar deposits of Illinois: J. M. Weller, R. M. Grogan, and F. E. Tippie (with con- tributions by L. E. Workman and A. H. Sutton). 1952. 147 p., 7 pis., 25 figs., 4 tables. $1.00. F. Bulletin 47. Geology and mineral resources of the Equality-Shawneetown area: Charles Butts. In cooperation with the U. S. Geol. Survey. 1925. 76 p., 3 pis., 6 figs. 50c. fied above. Details regarding the sandstone formations are given in these reports, which are available from the State Geological Survey, Urbana, Illinois. The salient data in the reports regarding the thickness and character of the sandstone are listed in table 1. NATURE OF SANDSTONE EXPOSURES The sandstones that crop out in southern Illinois are all more-or-less weathered from long exposure. Many of them are buff or brown owing to oxidation of iron-bearing minerals in them or to iron compounds that have been introduced into them. In some places relatively recent roadcuts suggest that the intensity of the buff or brown color decreases away from the outcrop. This is further suggested by the records of wells in southern Illinois that report the color of the sandstones as gray or white. The well data also indicate that some of the Upper Mississippian sandstones contain calcium carbonate some distance from the outcrops. Many of the outcrops are be- lieved to be noncalcareous, or essentially so, but a few samples did contain a small per- centage of calcium carbonate. The presence of calcareous material probably is undesira- ble in sandstone that is to be used as a source of silica sand. WORKABILITY OF DEPOSITS In the area covered by this report there are many deposits of sandstone. All the thicker sandstones form bluffs in some places. Overburden on many deposits is only loess, a silty clay. Near the Mississippi and Ohio rivers, the loess is as much as 60 feet thick in some places, but inland its thickness decreases rapidly and is about 5 to 10 feet in the north-central part of the area covered by this report. Judicious selec- tion of quarry sites may materially reduce the average thickness of loess overburden to be stripped from many deposits. Some sandstone deposits in southern Illi- nois crop out in bluffs and are overlain by limestone or shale formations in addition to the surficial loess. Such deposits presum- ably would have to be worked by under- ground mining. Underground mining may be preferable for certain sandstone strata having char- acteristics particularly suitable for certain purposes. This procedure is feasible under proper conditions as demonstrated by the DEPOSITS SAMPLED Table 1. — T HICK.NESS AND GENERAL CHARACTER OF SANDSTONES IN THE A reas Shown in Figure 1 Area A B c D E F Tradewater . Caseyville Degonia . Prob. thick* . .Thick locally* Thick* . .75-100'* Max. 75' Thick* Thick* 60-125' Thick* 100' or less' Thick* Thick* 35'f Mod. thick* Thick* X Palestine. Waltersburg . Tar Springs . Hardinsburg. . .40-60'* 30'* . .X 45'*f . .X 75' . .X Max. 40'*f 35-50'* 0-30'* 50-100'* 20-30'* 40-80'* 30-70' 40-100' f 30-100't 60'* 25-40'f 90'±* 70-120'* 60'* X 100-150'* 30-50' Cypress . Bethel . . Aux Vases . Thebes . . .X Max. 50' f . X X . .80' X . .X 75-100'+* well developed, not identified, or does not > of the formation are thin-bedded or sha uch or all of the formation is shaly. 70-80'* 5-10' X X crop out. y. 100'+ 15-130' X X 80-1 20' I 60-100'/ X X 200'+ X X X — ab.ent, not * — part or part t in places m underground mining of sandstone for silica sand in other areas. TESTING OF DEPOSITS Before commercial development is un- dertaken, test drilling or other exploration of deposits is recommended to determine the physical and chemical character of the un- weathered sandstone and to obtain detailed information on thickness of overburden, pos- sible presence of shale partings, calcareous zones, and other data related to the proper development of the deposit. SAMPLES Twenty-eight deposits, representing each of the principal sandstone formations in ex- treme southern Illinois, were carefully sam- pled at one or more places from road cuts and outcrops, by taking chunks at vertical intervals ranging between one and five feet. The deposits sampled are not necessarily those that may prove desirable for develop- ment should the sandstones have commer- cial importance ; the representative outcrops sampled were those that gave a maximum exposure of sandstone as little weathered as possible. Road cuts were preferred because the sandstone exposed in them was generally fresher than the stone in natural outcrops. Nevertheless, all the deposits sampled were more-or-less weathered, and many were buff or brown. The location and numbers of the sam- pled deposits are shown in figure 2. De- scription of these deposits follows. DEPOSITS SAMPLED 1 Cen. SEM SW^ sec. 30, T. 12 S., R. 1 E., along south bank Cypress Creek, SE of Anna, Union Co. Cypress sandstone. 25 ft. brown, cream, and pinkish sandstone in irregular, mostly thick beds. Sample 1A, upper 12^ ft.; IB, lower 12^ ft. 2 Cen. EH W3^ EK sec. 36, T. 9 S., R. 4 W., in gully in Fountain Bluff near Gorham, Jackson Co., near Illinois Central and Missouri Pacific railroads. Caseyville sandstone. Exposure consists of: 73 ft. — coarse-grained brown sandstone, in thick beds, with irregular iron-cemented bands. These bands may not be present in the un- weathered sandstone. Sample 2A. 15 ft. — coarse-grained brown sandstone, one solid bed, a few pebbles. Sample 2B. 17/^ ft. — medium-grained brown sandstone. Sample 2C. 30 ft. — coarse-grained brown slightly limy sandstone. Sample 2D. 35 ft. — fine-grained brown slightly limy sandstone. Sample 2E. Covered. The iron-oxide content of the sandstone at this place probably is higher than at some other places in the bluff. Exposures of sand- stone in the west side of the bluff appear to be lower in iron oxide. Cen. EV 2 W l A NWM sec. 20, T. 11 S., R. 1 W., road cut north of Cobden, Union Co., near Illinois Central Railroad. Degonia sandstone. 14 ft. white, brown, and red mottled sandstone. Sample 3. NWM NWM SWM sec. 1, T. 12 S., R. 1 W., road cut southwest of Saratoga, Union Co. Tar Springs sandstone. 33 ft. brown, buff, and red sandstone. Underlain by 4 ft. dark-gray shale. Sample 4A, top 16^ ft.; 4B, lower 163^ ft. ILLINOIS STATE GEOLOGICAL SURVEY Fig. 2. — Locations of sandstone outcrops sampled. SWM SEK SWM sec. 28, T. 10 S., R. 1 W., in gully and road cut near Makanda, Jackson Co., near Illinois Central Railroad. Caseyville sand- stone. Strata exposed are: 14 ft. — brown sandstone. 12 ft. — coal, shale, and carbonaceous sand- stone. 14 ft. — gray and white sandstone. 2 ft.— shale. Sample 5A, upper 14 ft.; 5B, lower 14 ft. W/ 2 SEM NWM sec. 24, T. 11 S., R. 1 E., in road gutter near Lick Creek, Union Co. Casey- ville sandstone. 45 ft. fine-grained white and buff sandstone. Sample 6A, upper 19 ft.; 6B, middle 19 ft.; 6C, basal 7 ft. EV 2 SE34 SEM sec. 17, T. 11 S., R. 1 E., in steep gully near Progress, Union Co. Caseyville sand- stone. 48 ft. soft brown sandstone. Sample 7A, upper 13 ft.; 7B, next lowest 4 ft.; 7C, next lowest 18 ft.; 7D, lower 9 ft. Basal 4 ft. too dirty to sample. NEK NWM sec. 4, T. 15 S., R. 3 W., along Illinois 3 at Gale, Alexander Co., near Missouri Pacific and C. & E. I. railroads. Thebes sand- stone. 20 ft. limy sandstone which weathers to thin beds. Upper 3 ft. brown, lower 17 ft. gray. Sample 8. Cen. EV 2 EV 2 sec. 15, T. 12 S., R. 3 E., road cut on U. S. 45 near Bloomfield, Johnson Co., near C. C. C. & St. Louis Railroad. Caseyville sand- stone. 35 ft. coarse-grained white and cream sand- stone. Sample 9A, top 11 ft.; 9B, next lowest 8 ft.; 9C, next lowest 11 ft.; 9D, basal 5 ft. 10 NW cor. SEM NWM sec. 20, T. 13 S., R. 2 E., road cut along Illinois 37 at north edge of Cypress and adjacent gully, Johnson Co., near C. & E. I. Railroad. Cypress sandstone. Exposure consists of: 22 ft. — white or cream friable sandstone, locally iron-stained — road cut. Sample 10A, top 10 ft.; 10B, lower 13 ft. 53^2 ft- — covered interval. 273^ ft. — yellow friable sandstone, in gully below road cut. Sample IOC. SE34 NWM sec. 27, T. 11 S., R. 3 E., in gully near Tunnel Hill, Johnson Co. Probably Trade- water sandstone. 54 ft. brown, reddish, and white well-cemented sandstone. Sample 11 A, upper 27 ft.; 11B, lower 27 ft. 12 W^ SEM sec. 17, T. 13 S., R. 5 E., in road cut along Illinois 146 near Dixon Springs, Pope Co. Palestine sandstone. 23 ft. of white, brown, and pinkish well-cemented sandstone. Sample 12A, upper 113^ ft.; 12B, lower 11^ ft- DEPOSITS SAMPLED 13 NV ? SWM sec. 13, T. 12 S., R. 5 E., near Glen- dale in a cut made in 1948 along road between Eddyville and Glendale, Pope Co. Caseyville sandstone. Exposure consists of: 14 ft. — white and ran fine-grained sandstone with about 3 ft. of interbedded shale. Sample 13A; does not include shale. 44 ft. — covered; probably sandstone. 9 ft. — tan sandstone. Sample 13B. 5 ft. — covered. 8 ft. — tan sandstone, Sample 13C. 6 ft. — tan sandstone, Sample 13D. 14 SYV34 SW^ NVV34 sec. 11, T. 14 S., R. 6 E., in road gutter near Homberg, Pope Co. Cypress sandstone. 20 ft. brown sandstone in weathered outcrop. Sample 14A, top 11 ft.; 14B, lower 9 ft., which is slightly limy. 15 NWM NE^ SWM sec. 30, T. 13 S., R. 7 E., abandoned quarry along Ohio River at Golconda, Pope Co. Cypress sandstone. 44 ft. of friable white or cream sandstone with brown specks and streaks. Sample 15A, top 11 ft.; 15B, middle 18 ft.; 15C, lower 15 ft. 16 SE^ SWM NEM sec. 34, T. 14 S., R. 6 E., in road gutter north of Bay City, Pope Co. Bethel sandstone. Exposure consists of: 9 x /2 ft. — white sandstone with iron-stained streaks. 5 ft. — covered interval. 20 ft. — buff, tan, and white sandstone. Sample 16A, top V/z ft.; 16B, next lowest 9 ft of sandstone exposed; 16C, the next lowest 12 ft.; 16D, the bottom 5 ft. 17 SW34 SWi^ sec. 22, T. 13 S., R. 6 E., in road cut near Waltersburg, Pope Co. Tar Springs sand- stone. 1\y 2 ft. white or cream sandstone; iron- stained in places. Sample 17. 18 NH NWM NEM sec. 28, T. 12 S., R. 7 E., in road cut northwest of Shetlerville, Pope Co. Hardinsburg sandstone. Exposure consists of: 23^2 ft. — white and tan sandstone. Sample 18A. 5 ft. — covered interval. 15 ft. — white firmly cemented sandstone with some brown iron streaks. Sample 18B. 19 NE cor. SE34 sec. 36, T. 13 S., R. 5 E., bluff at Brownfield, Pope Co., near Illinois Central Rail- road. Hardinsburg sandstone. 24 ft. slightly limy white and tan sandstone. Sample 19. 20 SE cor. SEK SW34 sec. 33, T. 10 S., R. 8 E., at High Knob near fire tower, near Karbers Ridge, Gallatin Co. Probably mostly Caseyville sand- stone. Strata exposed are: 12 ft. — medium- to coarse-grained white or pinkish sandstone, in places conglomeratic. Sample 20A. 9 ft. — coarse-grained mostly white sand- stone. Lower 5 ft. contains hard white parti- cles which may be chert. Sample 20B. 14^ ft. — medium-grained sandstone. Top 83^ ft. white, lower 6 ft. yellow and red. Sample 20C. 8 ft. — conglomeratic coarse-grained red and purplish sandstone. Sample 20D. 21 Sy 2 NV 2 N% sec. 9, T. 11 S., R. 7 E., in bluff along road near Herod, Pope Co. Caseyville sandstone. Strata exposed are: 25 ft. — mostly coarse-grained gray and brown sandstone. Sample 21A. 213^ ft. — medium-grained sandstone. Sam- ple 21B. 10)^ ft. — coarse-grained iron-stained sand- stone. Sample 21C. 22 NEM SW34 SW14 sec. 1, T. 12 S., R. 9 E., over- burden on quarry north of Cave in Rock, Hardin Co. Bethel sandstone. 353^2 ft- of fine- and me- dium-grained cream, white, and yellow sandstone. Sample 22A, from upper 18 ft.; 22 B, lower 173^ ft. 23 Wy 2 SE34 sec. 18, T. 13 S., R. 7 E., in bluff of Ohio River a short distance north of Golconda, Pope Co. Hardinsburg sandstone. 27 ft. of fine-, medium-, and coarse-grained white and tan sand- stone, in places yellow or brown. Sample 23. 24 Cen. Sy sec. 25, T. 11 S., R. 9 E., in road cut near Cave in Rock, Hardin Co. Hardinsburg sandstone. 21 ft. white and yellow sandstone. Sample 24A, from upper 9 ft. of outcrop; 24B, from lower 12 ft. 25 NE}4 NE}4 sec. 10, T. 11 S., R. 9 E., in road cut near Cadiz, Hardin Co. Tradewater sandstone. 20 ft. of fine- to coarse-grained mostly brown sand- stone. Sample 25. 26 1.6 miles northwest of Modoc in bluff on south side of mouth of Barbeau Hollow, on Modoc- Prairie du Rocher road, Randolph Co., near Mis- souri Pacific Railroad. Aux Vases sandstone. This area is not surveyed into sections. 83 feet of sand- stone, the upper 35 ft. tan, the lower 48 ft. some- what whiter. Sample 26A, from the top 31 ft. of sandstone; 26B, from the lower 52 ft. 27 N3^ SEM sec. 17, T. 8 S., R. 5 W., in bluff near Cora, Randolph Co., near Missouri Pacific Rail- road. Degonia sandstone. 31 ft. brown sandstone. Sample 27. 28 NWM NWM NEK sec. 18, T. 8 S., R. 5 W.. bluff at Rock wood, Randolph Co., near Missouri 10 ILLINOIS STATE GEOLOGICAL SURVEY Pacific Railroad. Palestine sandstone. 34 ft. tan sandstone in beds 6-13 ft. thick, separated by shaly layers up to 6 inches thick. Shale not included in sample 28 from this outcrop. 29 NWM SEM SWK sec. 11, T. 11 S., R. 7 E., Hardin Co., east of Herod. Bethel sandstone. Diamond drill core. Sample from depth of 622 to 659 feet. 30 Same location as 29. Cypress sandstone. Sam- ple from depth of 485 to 535 feet. 31 Same location as 29. Hardinsburg sandstone. Sample from depth of 285 to 312 feet. 32 Same location as 29. Tar Springs sandstone. Sample from depth of 85 to 108 feet. LABORATORY PREPARATION OF SAMPLES The samples taken from an outcrop were examined, disaggregated, and grouped into one or more "composite" samples on the basis of grain size. Thus, if an outcrop con- sisted of 30 feet of coarse-grained sandstone and 20 feet of fine-grained sandstone, the field samples from the upper 30 feet were combined, in amounts proportionate to the thickness of sandstone they represent, into a single composite sample. The samples from the lower 20 feet of sandstone would be similarly combined. DISAGGREGATION OF SAND- STONE No difficulty was experienced in disag- gregating the sandstone samples with a mortar and pestle. However, to obtain rough quantitative data on what might be expected from mechanical equipment, seven samples were treated as follows. About 500 grams of each sample was put through a laboratory jaw-crusher set at about 1/8 inch. A 50-gram sample of the crusher product was split out and sieved. The re- mainder was passed through a pair of lab- oratory rolls set at 1/16 inch for coarse sands, 1/32 inch for medium-grained sands, and set tight for fine sands. A 50-gram sample was split out and sieved. Another 50-gram sample was split out and processed in a mortar and pestle. A reasonably com- plete disaggregation results from the latter procedure. The results of sieve tests on samples processed as described above revealed no differences of more than 5 percent between those disaggregated by mortar and pestle and those by the rolls only. Much closer agreement was evident for most sieve sizes, especially in the case of the medium- and fine-grained sandstones. It is concluded from these tests that a reasonable degree of disaggregation of the outcropping sandstones probably is possible by mechanical means. MINERAL COMPOSITION The predominant component of the sand samples is quartz (silicon dioxide). Iron- oxide minerals (such as limonite) and clay occur in varying though commonly com- paratively small amounts. A few samples also contain a relatively small amount of calcite. Very small amounts of other min- erals were noted. These minerals are called heavy minerals because their specific grav- ity is greater than that of quartz. Informa- tion on the kind and approximate amount of these minerals in seven samples is given in table 2. Table 2. — Heavy Minerals in Sands 2A 2C 9C 10B 15B 24B 26B Total weigl ht percent f heavy mi nerals .09 .09 .13 .03 .2 .18 .1 Abundance* Leucoxene A A A A A A A Zircon C A VC A A A A Ilmenite VC VC R C VC C C Rutile VR VC C VC C C R Tourmaline C c VC VC C VC C Garnet R R R VR Anatase R R VC Hornblende VR Topaz VR Zoisite VR Muscovite R VC Hematite VR *A, abundant; VC, very common; C, common; R, rare; VR, very rare. MINERAL COMPOSITION 11 Plate 1. — A. Bethel sandstone, 35 by 65 mesh. Sample 16C. X 80. B. Caseyville sandstone, 28 by 65 mesh. Sample 9B. X 55. 12 ILLINOIS STATE GEOLOGICAL SURVEY Plate 2. — A. Coarse-grained Caseyville sandstone. Sample 2B. X 22. B. Probably Tradewater sandstone, 48 by 65 mesh. Sample 11 A. X 80. CHEMICAL ANALYSES 13 GRAIN SHAPE All the fine-grained sands studied have angular grains; the grains in the medium- and coarse-grained sands are more rounded but probably none of the sands can be classi- fied commercially as "round grain" sands (pis. 1 and 2). The secondary enlargement of sand grains by the addition of quartz is evident in many samples ; some samples con- tain grains that are almost perfect quartz crystals. Data covering a visual estimate of the grain shape of the samples otherwise investigated are given in table 3. SIEVE TESTS Sieve tests were made on each composite sample. The first step was disaggregation of the sandstone into its constituent par- ticles. This was done by crushing it me- chanically to about 1/4 inch and then rub- bing gently in the mortar with frequent hand sieving to remove the discrete sand grains. It is believed that relatively few grains were broken during disaggregation. In the coarser sieve sizes of a given sand, one particle out of about 200 was made up of two or, rarely, more sand grains. In the finer sizes, disaggregation appeared to be even more nearly complete. Table 3. — Grain Shape of Sands Very angular Samples 5A, 5B, and 8. Angular Samples IB, 3, 4A, 4B, 7B, 7C, 7D, 11A, 11B, 12A, 12B, 13A, 13B, 13D, 14A, 14B, 15B, 15C, 18A, 18B, 21A, 21C, 23, 24A, 25, 26A, 26B, 27, 28. Subangular Samples 1A, 6A, 6B, 6C, 7A, 9A, 10A, IOC, 13C, 15A, 16A, 16B, 16C, 16D, 17, 19, 21B, 22A, 22B, 24B. Subrounded Samples 9B, 9C, 10B, 20D. Coarse grains subrounded; fine grains angular Samples 2A, 2B, 2C, 2D, 2E, 9D, 20A, 20B, 20C. The disaggregated samples were shaken with water for one hour in an end-over-end shaker and then wet-screened on a 325-mesh sieve. The oversize was dried and screened on Tyler Standard Screen Scale sieves in a Rotap shaker for 10 minutes. The amount of minus-two micron material in the sam- ples was determined by means of the hy- drometer procedure. Clay, as defined by the American Foundrymen's Society, was deter- mined by procedures specified by that so- ciety. Results of sieve tests are given in table 4 together with grain fineness numbers calcu- lated in accordance with the procedure set up by the American Foundrymen's Society. CHEMICAL ANALYSES It was not feasible to make detailed chem- ical analyses of all samples taken during the investigation. However, 14 outcrop sam- ples were selected to represent the various sandstone formations exposed in southern Illinois and the variations in grain size. On the basis of these data, it was felt that the general commercial possibilities of the sand- stones could be assessed, leaving more ex- tended or additional analyses to those inter- ested in specific deposits. In addition to the outcrop samples, ana- lytical data also are given of four diamond drill core samples to indicate the nature of the sandstone at a considerable distance back from the outcrop. Samples were prepared for analysis in three ways: 1 ) Crude sandstone. — Portions of the dis- aggregated sandstone prepared for sieve an- alyses were used. Silica was determined by wet gravimetric chemical analysis; other data spectrographically. 2) Washed -(-270-mesh sand. — Portions of the disaggregated sandstone prepared for sieve analyses were used. Processing in- volved washing the sand in a laboratory "squirrel-cage" type scrubber and wet-siev- ing on a 270-mesh sieve. All chemical data were determined spectrographically except silica, which was determined by difference. 14 ILLINOIS STATE GEOLOGICAL SURVEY Table 4. Sample Near Thick- ness, feet T. R. 15S 3W 5N 9W 14S 6E 12S 9E 12S IE 13S 2E 14S 6E 13S 7E 12S 7E 13S 5E 13S 7E US 9E 12S 1W 13S 6E 13S 5E 8S 5W US 1VV 8S 5W 9S 4W 10 14 Alexander Randolph Pope Hardin Union Johnson Pope Pope Pope Pope Pope Hardin Union Pope Pope Randolph Union Randolph Jackson Gale Modoc Bay City Cave in Rock Anna Cypress Horn berg Golconda Gowins Brownfield Golconda Cave in Rock Saratoga Waltersburg Dixon Springs State Park Rockwood Cobden Cora Gorham 20 31 52 33^ 9 12 5 18 123^ ny 2 10 13 273^ 11 9 11 18 15 2V 2 15 24 27 9 12 163^ 213^ ny 2 uy 2 34 14 31 73 15 17^ NE NW Thebes Sandstone Aux Vases sandstone 1.6 miles NW of Modoc 34 SE SW NE NE SW SW cen.SE34 SW NW cor. SE NW SW SW NW NW NE SW W NW NE NE cor. SE wy 2 SE cen. Sy NW NW SW SW SW w^ SE NW NW NE cen. E3^ \\y 2 NW N^ SE cen. E3^2 W3^ Ey 2 Bethel sandstone 30 20 11 30 28 36 18 25 Cypress sandstone Hardinsburg sandstone 22 17 18 20 17 36 Tar Springs sandstone Palestine sandstone Degonia sandstone Caseyville sandstone 0.1 0.2 0.1 0.8 0.1 0.5 1.3 7.4 0.2 SIEVE TESTS 15 Sieve Tests Mesh size —Perce nt retained Sample 20 28 35 48 65 100 150 200 270 325 +2m* -2 M * A.F.S. clay* G.F.N.* 5.8 11.3 8.2 10.0 21.9 8.9 33.3 0.6 4.0 201 8 0.3 0.1 0.1 4.5 10.3 40.8 60.0 36.3 19.8 8.5 4.2 .9 .4 1.1 6.4 3.4 1.0 0.8 5.8 4.2 95 80 26A 26B 0.4 0.7 0.2 2.4 3.3 2.9 27.1 30.2 32.1 8.6 53.0 36.3 47.2 51.0 13.2 12.1 13.3 19.4 0.4 5.2 0.3 12.2 0.8 5.2 0.9 1.4 0.0 1.0 0.0 2.2 0.0 1.4 0.0 3.0 1.0 2.9 2.0 2.2 1.7 1.7 1.1 5.0 2.0 4.0 2.0 91 52 63 53 16A 16B 16C 16D 0.2 1.3 19.0 6.0 30.6 32.4 19.4 36.7 14.8 18.0 8.7 1.8 1.5 1.6 0.8 0.0 1.5 0.0 1.7 0.9 1.8 1.3 3.2 1.6 58 53 22A 22B 0.1 0.1 0.1 0.1 6.4 5.2 45.5 46.4 33.7 34.0 7.2 7.1 0.9 0.7 1.0 1.2 2.5 3.5 2.4 1.9 4.0 4.2 90 91 1A IB 0.2 0.2 0.2 0.2 0.2 10.7 6.8 2.6 24.0 49.2 38.7 38.0 34.2 45.5 15.3 4.7 6.1 4.6 2.0 3.3 1.0 0.1 0.2 0.8 0.4 0.2 2.4 1.4 1.7 2.8 0.8 1.5 3.3 1.2 2.4 77 64 68 10A 10B IOC 0.2 0.2 8.6 5.9 44.1 32.1 31.2 37.3 7.6 12.3 0.4 2.3 1.4 2.5 4.5 5.6 2.0 1.8 4.9 5.2 91 104 14A 14B 9.0 9.2 10.9 48.5 50.2 47.4 27.9 26.0 26.1 7.1 5.4 7.9 1.0 0.8 .9 1.3 1.4 2.0 3.2 5.1 2.5 2.0 1.9 2 3 4.7 3.8 4.1 88 92 89 15A 15B 15C 0.1 5.0 3.7 11 3 25.0 22.6 30.2 30.5 19.7 6.8 9.0 10.3 4.1 10.9 6.2 2.5 2.1 7.5 7.5 149 119 18A 18B 15.7 55.1 18.7 5.3 .2 1.1 1.9 2.0 2.5 82 19 1.6 22.7 47.0 17.9 4.4 0.6 0.6 3.5 1.7 3.9 79 23 0.2 0.2 6.7 8.2 37.1 51.4 41.0 28.3 9.0 5.7 0.9 1.1 1.1 1.3 2.6 3.1 1.2 0.9 3.0 2.9 93 88 24A 24B 2.0 4.5 29.1 44.3 48.2 38.3 11.8 6.3 2.9 3.7 0.4 0.2 0.2 0.2 3.2 0.1 2.2 2.4 4.6 2.4 72 65 4A 4B 8.7 56.4 23.6 5.2 0.9 1.1 2.5 1.6 4.0 83 17 0.2 0.2 1.8 0.2 5.6 9.2 30.8 34.8 34.2 26.3 14.1 13.2 2.1 3.0 2.7 5.7 6.2 5.4 2.3 2.0 4.4 3.2 108 113 12A 12B 4.9 20.5 38.8 19.2 2.7 3.7 8.7 1.5 7.4 116 28 5.3 29.6 37.6 14.5 2.5 4.0 5.0 1.5 5.7 107 3 4.0 18.0 32.9 24.4 4.0 5.9 8.9 1.9 7.2 127 27 10.4 16.9 1.1 61.1 20.8 8.7 13.5 9.6 8.3 2.0 6.9 10.9 1.2 8.4 18.3 2.2 13.5 27.2 1.3 6.6 13.0 1.2 2.5 5.0 0.2 0.4 0.8 0.1 0.5 1.1 3.9 4.5 2.5 1.3 2~3 2.1 1.5 2.6 34 51 70 2A 2B 2C 16 ILLINOIS STATE GEOLOGICAL SURVEY T ABLE 4.— Sample County Near Thick- ness, Va M X sec. T. R. feet 4 6 8 10 14 2D 2E 30 35 0.8 1.1 0.1 2.4 0.1 5A 5B Jackson Makanda 14 14 sw SE SW 28 10S 1W 9A 9B 9C 9D Johnson Bloomfield 11 8 11 5 cen. E3/2 ev 2 15 12S 3E 6.0 1.6 1.5 0.8 0.2 0.0 1.3 0.2 0.0 0.2 1.1 0.2 0.6 0.2 1.0 13A 13B 13C 13D Pope Glendale 14 9 8 6 N3^ sw 13 12S 5E 21A 21B 21C Pope Herod 25 10K SH N^ N3^ 9 US 7E 6A 6B 6C Union Lick Creek 19 19 7 NK SE NW 24 US IE 7A 7B 7C 7D Union Progress 13 4 18 9 E3^ SE SE 17 IIS IE 20A 20B 20C 20D Gallatin Karbers Ridge 12 9 143^ 8 SE cor. SEj^ SW 33 10S 8E Trader r ater s ands :one 25 Hardin Cadiz 20 NE NE 10 us 9E 11A 11B Johnson Tunnel Hill 27 27 SE NW 27 us 3E *+2m — finer than 325 mesh and coarser than 2 microns. -2/i — finer than 2 microns; principally clay. A.F.S. clay — clay as defined by the American Foundrymen's Society; finer than 20 microns. G.F.N. — grain fineness number as defined by the American Foundrymen's Society. (Concluded) SIEVE TESTS Mesh size- —Percent retained Sample 20 28 35 48 65 100 150 200 270 325 +2 M * -2 M * A.F.S. clay* G.F.N.* 4.1 0.2 17.9 0.2 21.6 0.9 25.4 10.2 14.1 28.3 5.9 45.5 1.4 10.0 0.9 0.3 0.1 0.5 0.2 0.5 1.7 1.4 2.4 1.8 2.5 2.6 41 67 2D 2E 3.8 0.2 26.8 6.6 32.8 54.3 18.7 25.0 6.9 3.4 0.9 0.9 1.8 1.9 5.7 4.6 2.6 3.1 5.6 6.4 87 88 5A 5B 0.8 1.0 0.2 1.4 6.3 9.8 3.7 5.5 10.1 22.7 12.7 14.5 22.4 35.6 21.0 28.0 31.3 14.8 31.0 19.0 16.3 6.1 18.4 9.3 2.8 1.4 3.4 3.1 2.6 1.6 0.6 1.4 0.2 0.0 0.2 0.4 1.3 0.6 0.4 0.6 4.1 2.4 4.3 5.0 1.4 1.6 2.2 1.6 3.7 4.0 5.0 4.0 58 42 54 51 9A 9B 9C 9D 0.2 0.1 0.4 0.1 0.0 5.1 0.1 0.2 4.7 27.7 12.0 8.9 30.0 45.5 59.1 59.0 41.2 11.2 15.5 20.4 14.8 3.3 4.4 5.1 2.2 0.6 0.8 0.9 2.2 2.1 1.8 1.6 2.4 1.2 3.7 2.0 2.2 2.9 2.5 1.9 4.0 3.7 4.2 2.6 102 75 86 86 13A 13B 13C 13D 2.2 2.1 3.2 7.2 8.0 9.2 58.0 57.5 50.9 24.0 19.3 21.1 3.6 5.3 6.2 0.2 1.5 1.7 0.0 0.9 1.3 0.0 0.0 0.0 0.0 0.0 0.0 1.9 2.8 3.2 2.9 2.6 3.2 3.6 3.6 3.3 46 49 53 21A 21B 21C 4.2 4.8 11.3 28.1 42.9 66.0 48.0 35.2 14.2 11.8 8.8 3.8 1.1 1.1 0.2 1.5 2.1 0.4 3.5 3.5 2.0 1.8 1.6 2.1 2.8 2.4 2.4 103 99 80 6A 6B 6C 0.4 4.5 7.0 4.0 10.2 35.1 28.0 32.2 48.8 29.8 38.5 53.5 30.2 21.8 17.3 5.4 4.9 4.5 2.7 2.4 2.3 1.4 1.9 0.0 0.0 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.9 1.0 2.6 2.0 2.1 1.5 1.4 2.1 2.1 1.6 3.2 66 62 57 56 7A 7B 7C 7D 4.3 0.8 23.9 10.0 6.7 1.4 33.3 11.5 30.3 12.4 24.9 17.0 45.4 40.8 10.5 19.6 8.7 31.6 2.1 24.6 5.1 8.9 0.6 5.5 0.0 0.7 0.0 2.0 0.0 1.2 0.0 0.4 0.0 0.0 0.0 0.1 0.0 0.0 0.0 3.7 1.6 1.3 2.8 1.3 1.4 1.7 1.9 3.3 2.0 3.0 3.6 56 40 46 26 20A 20B 20C 20D 0.2 1.3 9.5 25.2 28.7 15.2 3.1 4.5 9.0 3.3 8.8 113 25 0.2 0.2 0.4 0.8 0.9 11.5 13.0 33.3 37.8 29.6 27.6 8.9 6.2 5.4 3.8 0.9 0.6 2.0 1.0 5.1 6.4 2.1 2.3 6.0 3.8 75 77 11A 11B 18 ILLINOIS STATE GEOLOGICAL SURVEY Table 5. — Sandstone, Crude Samples (Analyses by Juanita Witters and L. D. McVicker in the laboratories of the Illinois State Geological Survey) Sample Formation Thick- ness Si0 2 Ti0 2 A1 2 3 Fe 2 Oa MgO CaO Na 2 K 2 Percent ay weigh t 2A 2B 2D Caseyville . Caseyville . Caseyville . 73 15 30 93.05 95.21 92.38 .35 .41 .20 1.5 1.6 1.8 4.2 1.5 2.8 .06 .04 .12 .07 .02 1.8 .00 .00 .01 .09 .13 .07 4A, B 6A, B 9A, B, C, D Tar Springs Caseyville . Caseyville . 33 38 35 97.71 96.58 96.27 .10 .39 .26 .9 1.5 1.8 .20 .42 .60 .04 .07 .07 .02 .02 .02 .00 .02 .02 .06 .16 .16 10A, B 11A, B 12A, B Cypress. Tradewater. Palestine 23 54 23 97.51 95.07 96.38 .08 .30 .30 1.1 2.2 1.6 .46 .91 .69 .03 .06 .07 .02 .03 .05 .03 .03 .02 .06 .34 .17 15A, B, C 22A,B 23 Cypress. Bethel .... Hardinsburg 44 36 26 97.31 97.54 97.42 .28 .16 .13 1.3 1.0 1.0 .27 .18 .46 .03 .07 .05 .06 .01 .03 .20 .01 .01 .07 .28 .15 26A, B 27 Aux Vases . Degonia. 83 31 95.54 92.77 .48 .60 1.8 2.6 .54 1.35 .06 .26 .03 .86 .03 .06 .39 .41 29* 30* 31* 32* Bethel .... Cypress. Hardinsburg Tar Springs 37 50 27 23 92.47 90.42 87.45 90.74 .40 .10 .18 .18 2.3 3.5 2.3 2.6 .30 .32 .90 1.23 .90 .72 1.11 .68 2.1 2.9 4.9 1.6 .04 .10 .05 .03 .60 .44 .40 .45 ♦Samples from diamond drill core. 3) Washed +270-mesh acid-treated sand with magnetic minerals removed. — Prepared by washing samples in "squirrel- cage" type scrubber, wet-sieving on a 270- mesh sieve, boiling with hydrochloric acid, and removing magnetic particles with a hand magnet. All analytical data were spectrographically determined. The crude sand, prepared by method 1, shows the chemical composition of the nat- ural unscreened sand. Analyses of samples prepared according to procedure 2 indicate the composition of the -j-270-mesh sand after washing and scrubbing. Analyses of samples prepared by procedure 3 suggest roughly what reduction in iron and titanium oxides might be expected in the washed -(-270-mesh sand if it were acid-treated and magnetic grains removed. The results of the analyses of the natural sandstones, table 5, show considerable varia- tion in composition. Samples 29 to 32 from the diamond drill core are relatively low in silica and high in alumina, magnesia, and lime, which suggests the presence of clay and the minerals calcite (calcium carbon- ate) and/or dolomite (calcium magnesium carbonate). Most of the other samples ap- pear to contain less clay and no calcite or dolomite, except possibly samples 2D and 27. The three number 2 samples are com- paratively high in iron oxide, which was ex- pectable because they were quite yellow or brown. Table 6 gives analyses of most of the samples in table 5 after they had been thor- oughly scrubbed in water and the material passing a 270-mesh sieve discarded. The result of the processing to which they were submitted was to remove clay, some iron oxide, and some fine sand. The percentage of silica in all samples was increased as a result of decrease in the amount of other compounds present. The average amounts of titania, alumina, soda, and lime were de- creased about 50 percent. Iron oxide, mag- nesia, and potassium were decreased an average of about 30 percent. Iron oxide re- mained high in the number 2 samples, sug- gesting the presence of particles of iron USES OF SANDSTONE 19 oxide or grains of clay and iron oxide ce- mented together that were not disaggre- gated during scrubbing. Table 7 shows data on titania and iron oxide in the samples after they had been heated in hydrochloric acid and the mag- netic grains removed with a hand magnet. These determinations were made because of the importance of iron oxide in some uses of sand. In all samples the decrease in iron oxide and titania, shown in table 7 as com- pared with table 6, probably can be expected to be accompanied by an increase in silica content by approximately the same percent- age. This is particularly significant for the number 2 samples. As a rule, acid and mag- net treatment decreased the iron oxide more than 90 percent below that of the washed samples. Titania was reduced by about 30 percent. USES OF SANDSTONE On the basis of laboratory data on out- crop samples alone, it is impossible to state definitely that a given sandstone deposit will constitute a commercial source of sand suitable for a specific use. A great deal de- pends on the uniformity of the deposit and the amount of processing given the sand- stone in preparing it for the market. Fur- ther, the specifications of a sand for a given use may vary considerably according to sev- eral factors, such as the preference of a con- sumer and the cost and availability of the sand. In view of this situation and the diffi- culty of finding satisfactorily detailed speci- fications for many of the uses of sand, the data that follow should not be interpreted as indicating specific uses for the sand sam- ples prepared from the sandstones of south- ern Illinois. Rather they point out fields of use that merit investigation as possible out- lets for the sands, providing that proper ex- ploration of the sandstone deposits and study of production procedures indicate that the sands can be produced economically. The data also suggest the kind of physical and chemical processing likely to be in- volved in preparing the sandstones and sands for market. Because of the availability of sand for structural and similar purposes from the Ohio and Mississippi rivers, it is uncertain whether southern Illinois sandstones ordi- narily can be crushed to compete advan- tageously in the structural-sand market. The best commercial opportunities are prob- ably in the field of silica sand. This will usually involve a processing operation, pos- Table 6. — Sandstone, Washed +270-Mesh Sand (Analyses by Juanita Witters in the laboratories of the Illinois St ate Geological S urvey) Sample Formation Thick- ness Si0 2 * Ti0 2 A1 2 3 Fe 2 O s MgO CaO Na 2 K 2 Percent by weight 2A 2B 2D Caseyville . Caseyville . Caseyville . . 73 . 15 . 30 94.29 98.47 96.74 .20 .07 .08 1.03 .58 .80 4.3 .78 1.3 .05 .03 .07 .05 .02 .94 .00 .00 .00 .08 .05 .07 4A, B 6A, B 9A, B, C, D Tar Springs Caseyville . Caseyville . . 33 . 38 . 35 99.34 98.51 98.55 .04 .20 .15 .34 .81 .72 .18 .28 .36 .02 .05 .04 .02 .02 .02 .00 .01 .01 .06 .12 .15 10A, B 11A, B 12A, B Cypress . Tradewater. Palestine . 23 . 54 . 23 99.13 98.22 98.08 .05 .15 .28 .47 .94 1.02 .25 .46 .41 .02 .04 .06 .02 .02 .02 .01 .01 .01 .05 .16 .12 15A, B, C 22A, B 23 Cypress . Bethel . . . Hardinsburg . 44 . 36 . 26 98.82 98.86 98.63 .13 .07 .12 .74 .66 .79 .15 .11 .32 .03 .05 .04 .02 .06 .02 .08 .01 .01 .03 .18 .07 26A, B 27 Aux Vases . Degonia ice. . 83 . 31 98.30 96.46 .10 .31 1.02 1.51 .29 .63 .04 .16 .02 .51 .02 .04 .21 .38 *By differei 20 ILLINOIS STATE GEOLOGICAL SURVEY Table 7. — Sandstone, Washed, Acid- and Magnet-Treated (Analyses by Juanita Witters in the laboratories of the Illinois State Geological Survey) Sample Ti0 2 Fe 2 3 Si0 2 * Percent by weight 2A 080 .053 98.2 2B 051 .032 99.0 2D 084 .050 97.5 4A, B 030 .027 99.5 6A, B 14 .047 98.8 9A, B, C, D. . .058 .032 98.9 10A, B . . . .020 .019 99.4 11A, B ... .10 .045 98.7 12A, B ... .13 .076 98.6 15A,B, C . . .22 .067 98.9 22A, B . . . .040 .021 99.0 23 092 .052 98.9 26A, B . . . .062 .049 98.6 27 16 .079 97.1 *Calculated by adding the differences between the per- cent of Ti0 2 and Fe.jO;, in tables 6 and 7 to the percent SiO., in table 6. sibly a considerable one. No generally ac- cepted definition of silica sand is known, but as a rule it contains more than 95 percent silica; many silica sands contain more than 97 percent silica. As a producer of silica sand commonly markets his sand for a vari- ety of purposes, one of which often is glass sand, many silica sands meet the specifica- tions for glass sand and contain more than 99 percent silica and less than .035 percent Fe 2 O s . Much silica sand is screened to produce various size grades, although unscreened silica sand of the proper natural grain size is sold for molding sand, furnace sand, and for other purposes. Many silica sands are washed to improve and purify them ; some are acid-treated to further increase the per- centage of silica content. The purposes of this investigation have not included extended exploration of the possibilities of improving the quality of the sand produced by crushing southern Illinois sandstone, by washing, acid treatment, and screening. However, the data given on particle size in table 4 show the sizes that can be produced by screening. The chem- ical analyses in tables 5, 6, and 7 present in- formation on a number of samples in their natural condition ; washed ; and washed, acid-treated, and magnet-treated. The data provide a basis for preliminary judgment of the effect of various types of processing in upgrading the character of the sand. POSSIBLE USES OF SANDS SAMPLED The following discussion relates to the sands produced by disaggregating the sam- ples. More extensive information is required to determine the uses of the deposits them- selves. The samples are classified below in three size groups. The limits of these groups are to some extent arbitrary and were set for convenience. Fine-grained sands (largely finer than 100 mesh and coarser than 270 mesh). — 6A, 8, 13A, 18A, 18B, 25, 27, and 28. Coarse-grained sands (finer than 4 mesh and largely coarser than 28 mesh). — 2A, 2B, and 20D. Medium-grained sands (largely finer than 28 mesh and coarser than 100 mesh). — all samples not listed above or in the fol- lowing category are medium-grained. Between medium- and fine-grained sands. — 1A, IB, 3, 6B, 12A, 12B, 14A, 14B, 24A, and 26A. Uses thought to merit further investiga- tion, particularly with reference to the mar- ket area for southern Illinois sands, are sug- gested below. There are, no doubt, other possible uses. Many require a carefully screened sand to meet size specifications. Sands containing more iron oxide and less silica than stated possibly can be used for some of the purposes mentioned, but suffi- ciently detailed specifications are not availa- ble to be specific. Structural uses are not included, for reasons previously mentioned. Whereas the following listing applies es- pecially to the samples tested, it also lays the groundwork for assessing the possibilities of outcrops not sampled. It is assumed that all sands are free, or essentially free, of calcium and magnesium carbonate. POSSIBLE USES OF SANDS SAMPLED 21 Crude sand samples (table 5) contain- ing more than 95% silica — synthetic mold- ing sand,* possibly furnace-bottom sand. Washed sand samples (table 6) contain- ing more than 95% silica. a) Coarse-grained sand — sand-blast- ing sand, filter sand, possibly synthetic molding sand. b) Medium-grained sand — traction sand, synthetic molding sand, core sand, sand for surface grinding of plate glass, possibly furnace-bottom sand. c) Fine-grained sand — synthetic molding sand, possibly glass-grinding sand, possibly furnace-bottom sand, pos- sibly some kinds of glass. Washed sand, acid-treated, with magnetic minerals removed (table 7) ; silica 99% or more; iron oxide less than ,035%.f "Synthetic molding sand also is referred to as "un- bonded" or "formulated" molding sand. ISample-; not meeting these specifications fall into the preceding category. a) Coarse-grained sand — synthetic molding sand, sand-blasting sand, filter sand, stone-sawing sand, sand for grind- ing to silica flour. b) Medium-grained sand — glass syn- thetic molding sand, sand for grinding to silica flour, traction sand, sand-blasting sand (generally coarser than 40 mesh), glass-grinding sand, filter sand, furnace- bottom sand, sand for sand lime brick, sand for chemical purposes such as so- dium silicate, carborundum, silicon metal, silicon tetrachloride and silicones, sand for prepared mortars and plasters, cata- lyst carrier. Possibly fracturing sand ; this use ordinarily is believed to require round-grain sand. c) Fine-grained sand — sand for grind- ing to silica flour, cement additive, sand for scouring soaps, core sand, molding sand. Illinois State Geological Survey, Report of Investigations 188 21 p., 2 pis., 2 figs., 7 tables, 1955 til