70

MANGANESE.

The only workable deposits of manganese yet defined by the Survey are those of the Central Mineral Region. These deposits are both in the form of manganese ores and of combinations of iron and manganese ores in different proportions.

The Spiller Mine, south of Fly Gap, Mason County, is the only known occurrence of the manganese ore on an extensive scale anywhere in the region, although surface croppings were traced, which seemed to indicate companion belts to the one which has been opened at the locality mentioned.

The ore is rather siliceous psilomelane, with patches of pyrolusite and more or less black wad, filling cavities and crevices in the vein, which is three or four feet wide. The ore seems to lie as an interbedded vein, and numerous borings were made on it with a diamond drill, presumably for the purpose of prospecting in the direction of its dip. Manganese ores are found under similar circumstances in the region between Packsaddle and Riley Mountains, and specimens are reported both from Gillespie and Blanco counties.

Manganese also occurs as an ingredient of the various limonitic ores, and in one instance such an ore was found to contain as much as eleven per cent of this metal in the form of dioxide. These deposits, however, are not likely to prove of much economic value.

BISMUTH.

Bismuth occurs in small quantities in connection with the ores of the Quitman range, and in one vein examined in the region of the Chinati Mountains as much as three and one-half per cent of this metal was found in the ore (galena).

ABRASIVES.

BUHRSTONE.

In the Fayette Sands are found stones of excellent quality for use as millstones. In Jasper and other counties millstones which have given perfect satisfaction in use have been cut from certain horizons of these sands.

GRINDSTONES.

Certain sandstones in the Carboniferous and older formations furnish"

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First Annual Report, p. 345.