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.