Occurs in masses or pebbles; at first grayish, but by exposure to the sun becomes uniform flesh, red or brown, never striped,—although Carnelian may form one of the bands of an Agate; brittle, breaking with a curved surface; very hard; takes a fine polish; glassy or resinous lustre; gravity 2.6.
Value.—Used for jewelry. When of two layers, white and red, (properly called sardonyx,) it is used for cameos.
Localities.—Same as Agate.
18.—Celestine.
Occurs crystallized, fibrous and massive; color white, often faint bluish; glassy lustre; very brittle; under the blow-pipe crackles and melts, tinging the flame red; does not dissolve in acids; gravity 4.
Value.—The source of nitrate of strontia, used in fire-works.
Localities.—Found in limestone, gypsum and sandstone. Rossie, Schoharie, Chaumont Bay, Depauville and Stark, N. Y.; Frankstown, Pa.; Strontian and Put-in-Bay Islands, Lake Erie; near Nashville, Tenn.; Fort Dodge, Iowa.
19.—Cerussite.
Occurs in crystals, in powder or masses; glassy lustre; brittle; dissolves in nitric acid with effervescence; heated strongly on charcoal crackles and fuses, giving a globule of lead; gravity 6.4.
Value.—A rich ore of lead yielding seventy-five per cent.