Erythrite, is a hydrous cobalt arsenate. Its name, derived from a Greek word meaning “red,” refers to erythrite’s crimson to pink color. The mineral is rare and unimportant but useful to the prospector as an indication of the presence of other cobalt minerals.
Erythrite crystals are translucent and have a diamondlike or glassy luster. The mineral occurs as a crust on rocks and as a crystalline aggregate in cracks, and in the form of an earthy powder it is knovvn as cobalt bloom. Notable locations of erythrite are at Cobalt, Ontario, and Schneeberg, Germany.
Composition, ; hardness, 1.5-2.5; specific gravity, 3.06; crystal system, monoclinic.