Gypsum (See also "Gypsum.") Gypsum is a hydrous calcium sulphate. In Arkansas it occurs most abundantly in the De Queen limestone member in the upper part of the Trinity formation, which is of Lower Cretaceous age. The outcrops of this gypsum are found in Pike and Howard Counties. The thickest exposure is in Plaster Bluff, where the gypsum forms a single bed ranging from ten to fourteen feet in thickness. This is pure saccharoidal gypsum, though there are some thin seams of satin spar and as much as three feet of interbedded clay in its lower part. To the west as far as Messers Creek, in Howard County, there are a few outcrops and reported occurrences of gypsum, but it is not everywhere pure, and at no place does its reported or observed thickness exceed three feet. A bed of selenite about two feet thick occurs in southern Drew County, in Townships 14 and 15 south, Ranges 6 and 7 west, in rocks of Tertiary age. Large fragments of selenite occur in Tertiary shales along the creeks near Redfield in Jefferson County, but it is probable that these will not be of commercial importance. For bibliography of "Gypsum" see bibliography at end of separate discussion on "Gypsum." 1. 2. 3. Bibliography of Arkansas Gypsum 1888 Hill, Robert T., "The Neozoic Geology of Arkansas."-Report of the Arkansas Geological Survey for 1888, Vol. II. Now out of print, but may be consulted in public or scientific libraries. 1892 Branner, J. C., "The Zinc and Lead Region of North Arkansas."— Report of the Arkansas Geological Survey for 1892, Vol. V. May be obtained from Arkansas Geological Survey, 447 State Capitol Buldg., Little Rock, Ark. 1920 Stone, Ralph Walter, and others, "Gypsum Deposits of the U. S."Bulletin of the U. S. Geological Survey No. 627. May be obtained from the U. S. Geological Survey, Washington, D. C., for 50c. 1924 4. Drake, N. F., "Mineral Fertilizers in Arkansas."-Obtainable from Bureau of Mines, Manufactures and Agriculture, State Capitol Building, Little Rock, Ark. Novaculite is a hard sileceous rock which is nearly pure silica. It is of sedimentary origin and was probably deposited as a sea sediment in the form of colloidal silica. The following is an analysis of a typical novaculite : Novaculites are usually of one of two classes which are known as the Arkansas stone and the Ouachita stone. The Arkansas stone is a very fine grained homogeneous stone and has a waxy luster and is usually white. This stone is preferred for making whetstones and is usually shipped rough in blocks weighing between five and fifteen pounds. The Ouachita stone is more porous than the Arkansas stone and has the appearance of unglazed porcelain. The demand for the Ouachita stone is much greater than that of the Arkansas stone and it is used in blocks up to 1,500 pounds or more for making large whetstones. The area in which novaculite is found in Arkansas is shown on the map on page 240. The novaculites are distributed around the edge of the central portion of the Ouachita Uplift in west-central Arkansas and there are probably between 300 and 500 miles of novaculite ridges in the State. In recent years the whetstone quarrying industry has been carried on only in a very small way in Arkansas on account of the competition of synthetic abrasives. The production of whetstone rock in Arkansas has been as follows: Recently large quantities of novaculite have been used by the Chicago, Rock Island & Pacific Railroad for railroad ballast. The novaculite does not disintegrate, is easily crushed and makes a durable roadbed. The novaculite quarry which supplies this materia! is located at Butterfield, Hot Spring County. 1. 2. Bibliography of Novaculite in Arkansas Wait, Charles E., "Analysis of Novaculite or Ouachita Whetstone from Hot Springs, Arkansas."-Bulletin of the American Journal of Science, Vol. 7, p. 520. Obtainable from American Journal of Science, New Haven, Conn. 1890 Prosser, Charles Smith, "The Geological Age of the Rocks in the Novaculite Area."-Annual Report of the Arkansas Geological Survey for 1890, Vol. III, pages 418-423. Now out of print, but may be consulted in public libraries. 3. 4. 5. 1891 Griswold, Leon, "The Novaculites of Arkansas" (Abstract).—American Association for the Advancement of Science, Bulletin 39, pages 248250. Obtainable from American Association for the Advancement of Science, Smithsonian Building, Washington, D. C. 1892 Griswold, "Whetstones and the Novaculites of Arkansas."-Annual Report of the Arkansas Geological Survey for 1890, Vol. III, "Novaculite." Now out of print, but may be consulted in public or scientific libraries. 1894 Hull, Edward, "Origin of the Novaculites of Arkansas."-Geological Society of London, Quarterly Journal, Vol. 1, p. 392. 1895 6. 7. 8. Griswold, Leon S., "The Origin of the Arkansas Novaculites."-Boston Society of Natural History, Tr. 26, pp. 414-421. Griswold, Leon S., "Indian Quarries in Arkansas."-Proceedings of Boston Society of Natural History, Vol. 26. 1898 Derby, Orville A., "On the Origin of Certain Siliceous Rocks; Notes on the Arkansas Novaculite."-Journal of Geology, Vol. 6, pp. 366-368. Obtainable from University of Chicago Press, Chicago, Ill. OCHRE Composition-The term "ochre" is often loosely used as a name for earthy pigments. As the term is usually used, however, it is an iron oxide or hydroxide associated with a clay base. Its specific gravity is about 3.5 and its color varies through various shades of red, brown, and yellow. The red variety is derived from hematite (ferric oxide) and the brown and yellow from limonite (ferric hydroxide). The yellow variety of ochre is known as mineral yellow, Roman earth, stone yellow, Chinese yellow, golden ochre, etc. Commercial yellow ochre is a natural ochre which sometimes contains a small percentage of chrome yellow. Burnt ochre is a red pigment made by calcining ochre at a high temperature. Red ochre is a natural pigment resembling burnt ochre. Gray ochre which has a greenish color contains some ferrous oxide and is used as a filler for a cheap paint. Cream ochre contains about 5% ferric hydroxide and is used as a filler for wood. White ochre is a common white clay. Good grades of ochre contains from 15% to 30% ferric oxide although there is a considerable variation in the amount of iron present in the material sold as ochre. Uses Ochre is used as a paint pigment, as coloring matter for plaster, stucco and concrete, and as a filler in the manufacture of linoleum and oil cloth. Occurrence Ochreous clay of excellent quality has been found in sections 7 and 8, Range 2 S, Township 12 W, Saline County, in the Tertiary clays present there. It occurs, however, in pockets and has not been found in any considerable amount, the pockets usually containing not more than 500 pounds of material. The ochre found there is of a bright yellow color. A small quantity of ochre has been found in the Tertiary clays in the southern portion of the city limits of Monticello, Drew County. Ochre of a similar nature has been found near Piggott, Clay County. The material, however, occurs only in small pockets. A reddish ochre is found in considerable quantity on the small branch of Hurricane Creek in the eastern portion of Range 2 S, Township 14 W, Saline County. A deep red oxide of iron occurs. abundantly in the openings of the American Bauxite Company at Bauxite. It is found in the Tertiary clays lying over the bauxite deposits and is usually in large nodules. Red ochre occurs in the Fourche Mountain district and in the suburbs of Little Rock. It is frequently possible to make a fair grade of paint by drying red or yellow clay and then grinding it with linseed oil. Such a paint will often wear well. Production-There is no commercial production of ochre in Arkansas at the present time. 1. Bibliography of Ochre 1889 Call, R. E., "The Geology of Crowleys Ridge," Annual Report of the Arkansas Geological Survey for 1889, Vol. II. Now out of print but may be consulted in public or scientific libraries. 1912 2. Hill, James M., "Mineral Paints," Mineral Resources of the United States, 1912, Part II, Non-Metals. Now out of print but may be consulted in public or scientific libraries. 1925 3. LaDoo, R. B., "Non-Metallic Minerals," pp. 377-380. Obtainable from McGraw Hill Book Company, 10th Ave. at 36th Street, New York City. |