VALUE.--An ore of copper, (containing thirty-three per cent.) and silver, of which Nevada specimens have sixteen per cent. 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. 38.--IRON PYRITES. Occurs in masses and square crystals; splendent lustre; color, bronze-yellow; brittle; strikes fire with steel; heated it gives off sulphur fumes; powder brownish; gravity 5. VALUE.--Affords sulphur, copperas and alum. When found outside of the coal region, it often contains gold and silver. LOCALITIES.--Found in all kinds of rocks. Bingham, Corinna, Farmington, Waterville, Brooksville, Peru and Jewett’s Island, Me.; Shelburne, Unity and Warren, N. H.; Baltimore, Hartford and Shoreham, Vt.; Heath, Hubbardston and Hawley, Mass.; Roxbury, Monroe, Orange, Milford, Middletown, Stafford, Colchester, Ashford, Tolland and Union, Conn.; Rossie, Malone, Phillips, Johnsburgh, Canton, Chester, Warwick and Franklin, Putnam and Orange Counties, N. Y.; Chester, Knauertown, Cornwall and Pottstown, Pa.; Greensboro’, N. C.; Mercer County, Ky.; Bainbridge, O.; Galena at Marsden’s Diggings, Ill.; on Sugar Creek, Ind.; mines of Colorado and California. 39.--JASPER. Occurs in masses, either in veins or as rounded stones; dull lustre, yet takes a high polish; breaks with a curved surface; not attacked by acids; is scratched by _Rock Crystal_; gravity 2.5.