bution of the limestones and dolomites is shown on the limestone map under "Building and Structural Stones."

Burned limestone or lime possesses the power of rapid reaction. with the soil and need not be expensive, because of the remarkable availability of the materials utilized in its manufacture. Here, again, local kilns of rather small capacity should prove profitable.

Lime producing plants are as follows:

1. St. Joe Lime & Stone Company (burnt and unburnt limestone products), St. Joe, Ark.

2. Ozark White Lime Company (manufacturers of burn lime. and hydrate), Fayetteville, Ark.

3. Batesville White Lime Company (manufacturers of burnt. lime and hydrate), Batesville, Arkansas. Plants at Limedale and. Ruddles, Ark.

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Bibliography of Limestone in Arkansas
1888

Hill, R. T., "Value of Lime as a Fertilizer and Discussion of Deposits at White Cliffs, Arkansas."-Arkansas Geological Survey Report of 1888, Vol. II, "Neozoic Geology of Southwestern Arkansas." Now out of print, but may be consulted in public or scientific libraries.

1890

Hopkins, T. C., "Lime Iudustry of Arkansas.”—Arkansas Geological Survey Report for 1890, Vol. IV, "Marbles and Other Limestones." Obtainable from Arkansas Geological Survey, 447 State Capitol Building, Little Rock, Ark.

Means, J. H., "Carboniferous Limestones on the South Side of the Boston Mountains.”—Arkansas Geological Survey Report for 1890, Vol. IV, "Marbles." Obtainable from Arkansas Geological Survey, 447 State Capitol Building, Little Rock, Ark.

1892

Harris, Gilbert D., "Tertiary.”—Annual Report of the Arkansas Geological Survey for 1892, Vol. II. Obtainable from Arkansas Geological Survey, 447 State Capitol Building, Little Rock, Ark.

1924

Drake, N. F., "Mineral Fertilizers in Arkansas."-Obtainable from Bureau of Mines, Manufactures and Agriculture, State Capitol Building, Little Rock, Ark.

Phosphates

The phosphate rock of Arkansas is not made up of one mineral, but of several. No special work has been done in an attempt to identify the mineral species containing the phosphate, but, judging from the chemical analyses of the rock, it is probable that three calcium phosphate minerals may be present, viz: Amorphous collophanite, a solid solution of calcium carbonate in calcium phosphate; dahllite, a hydrous calcium carbon phosphate; and some hydroapatite. There are probably some phosphates of iron and aluminum with calcium carbonate, quartz, clay, and manganese oxides. Iron and aluminum

are undesirable in excess of an aggregate total of from 5% to 6%, and it is their presence that lessens the value of Arkansas phosphate rock for the manufacture of commercial fertilizer.

The areas in which phosphates occur in Arkansas are shown on the accompanying map. The rock producing this fertilizer is of Ordovician age and lies below the St. Clair limestone of Silurian age (according to Ulrich). It is called the Cason shale and overlies the Polk Bayou limestone.

The only place where this phosphate rock has been developed in Arkansas is near the junction of East and West Lafferty Creek in the western part of Independence County. During 1906-1907, the Arkansas Fertilizer Company removed about 50,000 tons of crude phosphate rock from this area both by tunnelling and stripping. It was found, however, that Tennessee phosphate rock could be manufactured into acid phosphate as cheaply as the Arkansas rock, and the development of the Arkansas deposit was consequently discontinued. The Arkansas phosphate property is now being held as a reserve for future supply.

There are 20,000,000 tons of available phosphate rock in Arkansas, according to an estimate made by the U. S. Geological Survey in 1915. The outcrops of the phosphate horizon, shown on the accompanying map, are at least about 420 miles in length. At the present time, phosphate rock for the manufacture of acid phosphate is imported into Arkansas from Tennessee and Florida.

*The following are analyses of phosphate from northern Arkansas:

*Bulletin No. 74 of the Arkansas Experiment Station, Fayetteville, Ark., 1902, by J. C. Branner and J. F. Newsom, pp. 117-119.

The Arkansas Fertilizer Company of North Little Rock, and the Capitol City Acid Phosphate Company, Box 151, Little Rock, Ark., are the only manufacturers of acid phosphate in the State at present (December, 1926).

Aside from the possible use of Arkansas phosphate rock in the manufacture of acid phosphate, it may be used advantageously in the raw state. This rock does not contain any so-called soluble phosphate but if this material is crushed and mixed with the soil it very slowly changes to soluble phosphates through the action of ground waters and organic acids. Through this process it is estimated that, over a period of five years, about 25 per cent of insoluble phosphate is made available for plant use. Thus agricultural lands should receive long-period benefits from the application of the raw phosphate rock.

In view of the increasing need of commercial fertilizers containing phosphate, and the desirability of securing a cheaper supply of phosphate that may be applied raw, further work should be made. in exploration and evaluation of the phosphate rocks of Arkansas. There is no production of phosphate in Arkansas at present.

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Bibliography of Phosphates

1886

Penrose, R. A. F., Jr., “Nature and Origin of Deposits of Phosphate of Lime," Bulletin No. 46 of the U. S. Geological Survey. Now out of print but may be consulted in public or scientific libraries.

1897

Branner, J. C., "The Phosphate Deposits of Arkansas."-American Institute of Mining Engineers Journal, Tr. 26, pp. 580-598. Obtainable from American Institute of Mining Engineers, 29 W. 39th Street, New York City.

1902

Branner, J. C., and Newsom, John F., "The Phosphate Rocks of Arkansas."-Agricultural Experiment Station Bulletin No. 74. Now out of print, but may be consulted in the University of Arkansas library, or public libraries.

1906

Purdue, A. H., "Developed Phosphate Deposits of North Arkansas."-Bulletin No. 315p of the U. S. Geological Survey, pp. 463-473. Now out of print, but may be consulted in public libraries.

1907

Purdue, A. H., "The Phosphates of North Arkansas."-Engineering and Mining Journal, Vol. 83, p. 1038. Obtainable from McGraw-Hill Book Company, 10th Avenue at 36th Street, New York City.

1918

Phalen, William C., "The Conservation of the Phosphate Rock in the United States."-American Institute of Mining Engineers Journal, Tr. 57, pp. 99-132. Obtainable from American Institute of Mining Engineers, 29 W. 39th Street, New York City.

1924

Drake, N. F., "Mineral Fertilizers in Arkansas." Obtainable from Bureau of Mines, Manufactures and Agriculture, State Capitol Building. Little Rock, Ark.

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."

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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.

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1892

May be

Branner, J. C., "The Zinc and Lead Region of North Arkansas."Report of the Arkansas Geological Survey for 1892, Vol. V. 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.