13.—Brittle Silver Ore.
Occurs in crystals and masses; metallic lustre; tarnishes yellow, gray and finally black; easily cut or broken; when heated gives off fumes of sulphur and antimony, affording a button of silver; dissolved in nitric acid, it silvers copper placed in it; gravity 6.
Value.—A rich ore of silver, containing over sixty per cent.
Localities.—Found in veins with other silver ores, in Nevada and Idaho.