Mimetesite
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Mineral NameMimetesite
Chemical FormulaPb5(AsO4)3Cl
Mohs Hardness3.5
Crystal Systemhexagonal
Streak ColorWhite to yellowish-white
CleavageImperfect on {1010}
FractureUneven to conchoidal
Specific Gravity7.24
Colorsyellow, chartreuse
TransparencyTransparent to translucent
Type LocalityTsumeb Mine, Tsumeb, Oshikoto Region, Namibia
Mineral GroupPhosphates, Arsenates, Vanadates (Apatite Group)
Usescollector's specimens, minor lead ore
Associated Mineralscerussite, malachite, azurite, smithsonite, duftite
Description
This image displays several bright yellow to chartreuse mimetesite crystals, exhibiting excellent hexagonal prismatic forms with sharp terminations, growing on a dark, granular matrix. The crystals show a distinct resinous to adamantine luster.
Geological Context
Mimetesite is a secondary mineral found in the oxidized zones of lead-bearing hydrothermal ore deposits, forming from the alteration of primary lead minerals in the presence of arsenic. It is characteristic of highly oxidized polymetallic deposits such as the Tsumeb Mine.
