Occurs crystallized and massive; does not scratch glass easily; metallic lustre; tarnish, copper-red; powder, blackish-gray; brittle; heated on charcoal gives off sulphur fumes; heated with borax gives a blue glass; gravity 5.
Value.—An ore of cobalt, yielding twenty per cent.
Localities.—Usually found in slate or granite rocks with Copper Pyrites. Mineral Hill, Md.; Mine-la-Motte, Mo.
23.—Copper.
Occurs in irregular masses; metallic lustre; can be cut with a knife; malleable; ductile; fusible; gravity 8.8.
Value.—A source of copper and silver.
Localities.—Most abundant in the trap and “freestone” regions. New Brunswick, Somerville, Schuyler’s and Flemington, N. J.; Whately, Mass.; Cornwall and Shannonville, Pa.; Polk County, Tenn.; Keweenaw Point, Lake Superior; Calaveras, Amador and Santa Barbara Counties, Cal.; on Gila River, Ariz.
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.