56.—Rensselaerite.
Occurs in masses; wax-like; a trifle harder than marble; when fresh can be scratched by the nail; soapy feel; takes a polish; cleavable; gravity 2.8.
Value.—Used as a marble and worked into inkstands, etc.
Localities.—Found with steatite, serpentine, limestone, etc. Antwerp, Canton, Fowler, De Kalb, Edwards, Russell and Gouverneur, N. Y.
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.
58.—Rock Salt.
Occurs in irregular beds or masses; brittle; saline taste; crackles in the fire.