51.—Oxyd of Manganese.
Occurs in masses and little columns, often with small rounded surfaces; one ore is soft enough to be impressed by the nail, and soils; the other will scratch glass faintly; heated with borax, makes a violet glass; dissolves in hot muriatic acid, giving forth a yellowish-green gas; gravity 4 to 5.
Value.—Used for bleaching and for obtaining oxygen.
Localities.—Found in granite regions, often with iron-ore. Brandon, Bennington, Monkton, Irasburg and Chittenden, Vt.; Hillsdale, Westmoreland and Westchester, N. H.; Plainfield, West Stockbridge and Conway, Mass.; Salisbury and Kent, Conn.; Montgomery County, Md.; Lake Superior Mining Region; Dubuque, Iowa; Deep Diggings, Mo.; Red Island, Cal.; Martinsburg, N. Y.
52.—Platinum.
Occurs in grains or lumps; metallic, silvery lustre; can be hammered out; heavier and harder than silver; not dissolved in nitric acid; gravity 17.
Value.—Nearly equal to Gold. Used for making chemical and philosophical apparatus, for coating copper, brass, etc.
Localities.—Found in river-gravel with Gold. Rutherford County, N. C.; Klamath region, Cape Blanco, on Salmon River, South Fork of Trinity, Butte, Honcut, Cañon and Wood’s Creeks, and on Middle Fork of American River, Cal.; at Gold Flat, Nev.
53.—Red Copper Ore.
Occurs in crystals and masses; cochineal-red; powder brownish-red; nearly opaque; brittle; dissolves in nitric acid; heated on charcoal yields a globule of copper; gravity 6.