Localities.—Found with gold, silver and lead. Kellogg Mines, Ark.; Mariposa and Shasta Counties, Cal.; Sheba and De Soto Mines, and near Austin, Nev.; Heintzelman and Santa Rita Mines, Arizona.
36.—Gypsum.
Occurs in plates, fibres coarse and fine, and massive; pearly or glistening; powder white, which if heated and mixed with water, turns hard; does not dissolve in sulphuric acid; may be scratched by the nail; gravity 2.3.
Value.—Used for stucco, manure, glazing, statuary, manufacture of glass, etc. A variety, called Satin Spar, worked into necklace beads and other ornaments, is finely fibrous and compact, taking a polish (though easily scratched,) and then resembles pearl or opal.
Localities.—Found with marl or clay, limestone and salt. Camillus, Manlius, Stark and Lockport, N. Y.; on the St. Mary’s and Patuxent, Md.; Washington County and Lynchburg, Va.; Charleston, S. C.; Poland, Ottawa and Canfield, O.; Davidson and Summer Counties, Tenn.; Grand Rapids and Sagenaw Bay, Mich.; Des Moines River, Iowa; Walker Lake and Six Mile Cañon, Nev.; Fort Dodge.
37.—Horn Silver.
Occurs in crystals, wax-like masses, or in crusts; when scratched shows a shining streak; becomes brown on exposure; quite soft, easily cut; a small piece placed on zinc and moistened, swells up, turns black and shows metallic silver on being pressed with a knife; dissolves in hartshorn; gravity 5.5.
Value.—An ore of silver, yielding seventy per cent.
Localities.-Found in slate with other silver ores. Lake Superior Mining Region; Austin and Comstock Lode, Nev.; Willow Springs and San Francisco districts, Eldorado Cañon, Ariz.; Poorman Mine, Idaho.