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(from the Greek mimetes, “imitator,” in allusion to mimetite’s resemblance to pyromorphite), also mimetesite, a mineral; a complex lead arsenate of chemical composition Pbs [AsO4]3Cl, often containing P2O5, CaO, and other admixtures. Mimetite crystallizes in the hexagonal system, forming minute prismatic, more rarely acicular, crystals with a high luster. Its crystal structure resembles that of apatite. Usually of pale yellowish green or yellowish brown color, mimetite has a hardness of 3.5 on Mohs’ scale and a density of 7,190–7,250 kg/m3. The mineral gives off a strong garlic odor upon heating, owing to the presence of As.
Mimetite is formed in the oxidized zones of hydrothermal deposits as a result of the oxidation and decomposition of lead ores, as well as in the presence of lennantite, arsenopyrite, or any other arsenides and sulfoarsenides. It is a rare mineral.