24.—Copper Glance.
Occurs crystallized and massive; color, blackish lead-gray, often tarnished blue or green; nearly as hard as marble; brittle; a splinter will melt in a candle, giving off the odor of sulphur; dissolved in nitric acid, it will coat a knife-blade with copper; metallic lustre; gravity 5.5.
Value.—An ore of copper, yielding seventy-five per cent.
Localities.—Found at copper-mines. Simsbury, Bristol and Cheshire, Conn.; Schuyler’s Mines, N. J.; Orange County, Va.; near Newmarket, Md.; Lake Superior copper-region; La Paz, Arizona; Washoe, Humboldt, Nye and Churchill Counties, Nev.