Localities in Pulaski, Garland, Hot Spring, Montgomery, Pike, Howard, Sevier, Polk, Scott and Logan Counties have been fitfully and unprofitably exploited for silver at various times in the past. Some of the lead-bearing shales of the Arkansas River Valley contain from five-tenths to one ounce of silver to the ton. Up to the present time, however, no deposits large enough to be of commercial importance have been discovered.

For bibliography of "Silver" see "Bibliography of Gold and Silver."

GYPSUM

Composition.-Gypsum is calcium sulphate containing water of crystallization. Pure gypsum is seldom found in nature, as most deposits contain oxides of iron and aluminum, carbonate of calcium and magnesium, and other impurities. It occurs as rock gypsum, selenite, and satin spar.

Arkansas gypsum occurs as saccharoidal or rock gypsum which resembles soft lump sugar; satin spar, which has a silky, fibrous appearance; and selenite, which is clear crystalline gypsum.

Uses. The uncalcined gypsum is used, principally, as a retarder for cement. Other uses are as a fertilizer, a disinfectant, making blackboard crayon, as a base for paints, as a filler for cotton, in the manufacture of nearly all the finer grades of paper, and, in some arid sections of the western states, as road metal and building material. Finely grained semi-translucent rock gypsum or alabaster is used by sculptors and artists for statuary and other forms of decoration. The principal use of calcined or dehydrated gypsum, known as "plaster of paris," is for wall plaster. The gypsum occurring in southwest Arkansas has been used principally to make plaster of paris, and as a fertilizer. The gypsiferous marls which occur along with the gypsum are suitable only for an agricultural fertilizer or land plaster.

Occurrence. The most noticeable outcrop of gypsum in Arkansas is in the southwestern part of the State in Pike and Howard

Counties. It occurs in the De Queen limestone member of the upper Trinity formation of Lower Cretaceous age and is exposed in a narrow belt extending westward from Plaster Bluff on the Little Missouri River, Howard County, through Sevier County, into Oklahoma.

In the north half of the northwest quarter of Section 31, Township 8 south, Range 35 west, at Plaster Bluff on the river bank, there is an exposure of gypsum 450 feet in length and twelve feet thick. Above it is forty-five feet of Cretaceous limestone and clay which has an overburden ranging from twenty to thirty feet. The lease is owned by John T. Riley, Kansas City, Mo. This outcrop consists of pure saccharoidal gypsum with thin seams of satin spar and some clay interbedded in it.

The Certainteed Products Company drilled holes at Highland, Pike County, where they found gypsum in variable thicknesses from two to four feet. The deposits were in the southeast quarter of the northeast quarter of Section 21, Township 8, Range 26; also in Section 22, Township 8, Range 26.

Disjointed selinite (crystalline gypsum) crops out in Jefferson County at Redfield. Other deposits are in townships 14 and 15 south, ranges 6 and 7 west, near the Ashley, Drew & Northern Railway. The latter are about two feet in thickness.

Crystalline, fibrous and earthy gypsum occurs in small amounts, often in broad crystals, in the lead and zinc districts of northern Arkansas.

The quality of Arkansas gypsum varies. In some places in the State it is pure enough to be of commercial value provided the market price is sufficient to justify the expenses of mining and transportation, while in other places it is so impure that it can only be used locally as a fertilizer.

Production. Gypsum has not been commercially produced in Arkansas except in 1922, when 600 short tons were sold for $1,800.00.

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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.

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 Bldg., Little Rock, Ark.

1920

Stone, Ralph Walter, and others, "Gypsum Deposits of the U. S."Bulletin of the U. S. Geological Survey No. 697. May be obtained from the U. S. Geological Survey, Washington, D. C., for 50c.

1924

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

IRON

The following is taken from the Annual Report of Arkansas Geological Survey, 1892, Vol. I, "The Iron Deposits of Arkansas," by A. F. Penrose, Jr.:

Composition. "The commercial value of the iron ores of Arkansas are usually, if not always, non-Bessemer in quality, generally containing over 0.05 per cent of phosphorus; in iron they vary from less than 35 per cent to over 55 per cent; in silica they vary from rarely as low as 2 per cent to over 75 per cent, and are often much injured by an excess of this ingredient; in sulphur they range from 0.04 per cent to rarely over 1 per cent; in some localities they contain enough manganese to be classed as manganiferous iron ores; only the magnetite of Magnet Cove contains titanium in appreciable quantities.

"Most all the iron ores of Arkansas belong to the class of hydrous sesquioxides of iron, or limonite, commercially called brown hematite, or simply "brown ore." The only other ores found in the State are limited quantities of carbonate of iron or spathic ore, also known as clay-ironstone, found in the Carboniferous shales and in the Tertiary clays and sands, and still more limited quantities of magnetic ore (magnetite) occurring in a residual clay derived from the decay of crystalline rock in Magnet Cove. This last ore is the celebrated Arkansas lode stone, and has attracted more attention than any other iron deposit in the State.

Occurrence. "Iron ore is of common occurrence throughout many parts of Arkansas, but in only a few places is it found in important quantities. The largest and most accessible deposits yet discovered are in the northeastern part of the State, especially in Lawrence and Sharp, and to a lesser extent in Fulton and Randolph Counties. Other deposits, however, of varying size and importance occur in many places in different parts of the State.

"In the descriptions of the various iron ore localities of Arkansas, the State will be divided, for the sake of convenience, into five different parts, as follows:

"1. The Iron Deposits of Northeastern Arkansas.-(Lawrence, Sharp, Fulton and Randolph Counties.)

"2. The Iron Deposits of Northwestern Arkansas.-(Carroll, Washington and Madison Counties.)

"3. The Iron Deposits of the Arkansas Valley.-(Van Buren, Conway, Pope, Yell, Johnson, Logan, Franklin, Sebastian, Scott and Crawford Counties.)

"4. The Iron Deposits of the Ouachita Mountains.-(Pulaski, the northern part of Saline, Hot Spring, Clark, Pike, Montgomery and Polk Counties.)

"5. The Iron Deposits of Southern Arkansas.-(The southern part of Saline County, Dallas, Ouachita, Nevada, Hempstead and Lafayette Counties.)

"The ores of northeastern Arkansas are associated with Lower Silurian (probably Calciferous) sandstones, cherts and limestones; the ores of northwestern Arkansas, in the central part of Carroll County, occur mostly with Lower Silurian cherts, while those of Washington and Madison Counties are mostly in Lower Carboniferous sandstones; the ores of the Arkansas Valley occur almost exclusively with rocks of Carboniferous and Lower Carboniferous ages, though some of them are much later deposits formed by the concentration, at the mouths of springs, of the iron in rocks of those ages; the ores of the Ouachita Mountains occur mostly with Lower Silurian shales and novaculites, though they also include the magnetic ore of Magnet Cove, which occurs in an area of igneous rock in the novaculite region; the ores of the southern part of the State are in a great series of sands and clays which represents the Eocene division of the Tertiary.

The Iron Mining Possibilities of Arkansas

"Conditions Necessary for Profitable Iron Mining.—The value of an iron ore deposit depends as much on its geographic position, its relation to transportation and markets, and the facilities for mining, as it does on the quality of the ore. Moreover, if furnaces are to be erected for the manufacture of pig-iron, the distance of fuel, and of limestone for fluxing purposes, are most important points to consider. In determining the value of an iron deposit, therefore, four main subjects must be taken into consideration:

"I. The quality and quantity of the ore.

"II. The facilities for mining the ore.

"III. The relations of the deposits to transportation and to

markets.

"IV. The relations of the deposit to fuel and limestone.

"Conditions in Northeastern Arkansas.-In the northeastern part of the State there are some isolated deposits of fairly good brown hematite which, if they had transportation facilities and markets, might be worked at a profit. The facilities for mining the ore in this region are good. It occurs on isolated hills and ridges rising from fifty to over three hundred feet above the surrounding drainage. It forms irregularly shaped bodies from two or three to probably over twenty-five feet in thickness, and often covering several acres, generally lying in a horizontal position and usually on or near the summits of the hills. Though limited in both lateral and vertical extent, the ore that is in any one place lies near the surface and could be easily mined. The nearest means of transportation for the ore of

northeastern Arkansas is the Kansas City, Fort Scott & Memphis Railway, which is from eight to twenty miles distant from the more important deposits. The Black River flows through the northeastern part of the State and in some localities freight might be shipped down it to the White River and thence to the Mississippi. The transportation facilities, however, cannot at present be considered as good, since, unless a branch road were built, a haul by wagon of from eight to twenty miles would be necessary to reach either the railway or the river. The nearest coking coal to the iron deposits of northeastern Arkansas is that of Western Arkansas and of Oklahoma, at distances by rail varying from 225 to over 400 miles. Good hardwood, however, fit for making charcoal, is plentiful in the vicinity of the ore, and a fairly pure limestone can also be obtained in the same region.

"In consideration, therefore, of the combination of a fairly good ore with a cheap charcoal, made from the timber of the region, and with limestone in the immediate vicinity, there is a possibility of a limited iron industry in northeastern Arkansas.

"Conditions in Northwestern Arkansas.-The ores in the northwestern part of the State, aside from any questions of quality, are in too small quantities to be profitably worked.

"Conditions in the Arkansas Valley. In the Arkansas valley the ores are too poor in quality and occur in too small quantities to be of any value as sources of iron.

"Condition in the Ouachita Mountains.—In the Ouachita Mountains the only ores yet found in large quantities are of low grade. The deposits dip steeply and would be expensive to mine. The nearest railways are from seven to, more generally, over twenty miles and often over forty miles distant. Limestone is scarce and often altogether absent in the Ouachita Mountains, and there is no coal nearer than the Arkansas Valley, with which region the Ouachita Mountains have no direct railway connection. There is, however, a large amount of timber, and with cheap charcoal fuel there is always at least a possibility of the future utilization of the better class of ores. The industry, however, would never be an important one, and could only be carried on under the most favorable conditions of transportation and markets, conditions which at present are far from being realized.

"Conditions in Southern Arkansas.-In the southern part of the State the Tertiary brown hematites occur over considerable areas, but the ores which are of sufficiently good quality to use are so scattered that it is somewhat doubful whether enough can be found in one place to permit important mining. Large deposits of poor ore frequently occur in this region, but they are of too low grade to be of value. The better ores are mostly from eight to fifteen miles from the nearest railway transportation, which is the St. Louis, Iron Mountain & Southern Railway or the St. Louis & Southwestern Railway. Lime