57.—Rock Crystal.
Occurs in crystals and masses; transparent; glassy lustre; colorless; tough; brittle; not acted upon by acids or heat; electric by friction; gravity 2.5.
Value.—Cut for ornaments, lenses, etc.
Localities.—Common in sandstone, limestone and iron ore. Paris, Me.; Benton and Bartlett, N. H.; Sharon and Woodstock, Vt.; Pelham and Chesterfield, Mass.; Ellenville, Little Falls, Watervliet, Fairfield, Middleville, Fowler, Antwerp, Rossie, Lake George and Palatine, N. Y.; Minnesota Mine, Lake Superior; Ouachita Spring, Ark.