Enargite

Infobox mineral
name = Enargite
category = Minreral: Sulfide
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caption = 2cm specimen of Enargite crystals on pyrite from Butte, Montana
formula = Cu₃AsS₄
molweight = 393.82 gm
color = Greyish Black to Black
habit = massive to well crystaline
system = Orthorhombic
twinning =
cleavage = Perfect [110] , Distinct [100] & [010]
fracture = uneven
tenacity = Brittle
mohs = 3
luster = Metallic
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fluorescence= None
absorption =
streak = Black
gravity = 4.4 to 4.5
density =
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diaphaneity = Opaque
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references = [http://www.mindat.org/min-1380.html Mindat] [http://webmineral.com/data/Enargite.shtml Webmineral] [http://mineral.galleries.com/minerals/sulfides/enargite/enargite.htm Mineral galleries]

Enargite is a copper arsenic sulfosalt mineral with formula: Cu₃AsS₄. It takes its name from the Greek word enarge, "distinct." Enargite is a steel gray, blackish gray, to violet black mineral with metallic luster. It forms slender orthorhombic prisms as well as massive aggregates. It has a hardness of 3 and a specific gravity of 4.45. It is a medium to low temperature hydrothermal mineral occurring with quartz, pyrite, as well as other copper sulfides. It occurs in the mineral deposits at Butte, Montana, San Juan Mountains, Colorado and at both Bingham Canyon and Tintic, Utah. It is also found in the copper mines of Canada, Mexico, Argentina, Chile, Peru, and the Philippines.

Enargite was originally described as a new species from the copper mines of the San Francisco vein, Junin Department, Peru

References