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Enargite

{{Infobox mineral | name = Enargite | category = Sulfide mineral | boxwidth = | boxbgcolor = | image = Enargite-122840.jpg | imagesize = 260px | caption = | formula = Cu3AsS4 | strunz = 2.KA.05 | system = Orthorhombic | class = Pyramidal (mm2)
H-M symbol: (mm2) | symmetry = Pmn21 | unit cell = a = 7.407(1), b = 6.436(1)
c = 6.154(1) [Å]; Z = 2 | color = Grayish black to iron black; gray to pale pink-brown, deep red internal reflections in polished section | habit = Tabular to prismatic crystals, striated parallel to {001}; massive | twinning = Twin plane {320} common, rarely as interpenetrating pseudohexagonal trillings | cleavage = Perfect on {110}, distinct {100} and {010} | fracture = Uneven | tenacity = Brittle | mohs = 3 | luster = Metallic to dull | polish = | refractive = | opticalprop = | birefringence = | dispersion = | pleochroism = | fluorescence= | absorption = | streak = Black | gravity = 4.4 to 4.5 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Opaque | other = | references = }} Enargite is a copper arsenic sulfosalt mineral with formula: Cu3AsS4. It takes its name from the Greek word , "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.

Enargite is dimorph of the tetragonal luzonite.

Occurrence

It is a medium to low temperature hydrothermal mineral occurring with quartz, pyrite, sphalerite, galena, bornite, tetrahedrite–tennantite, chalcocite, covellite and baryte. 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. The name is from Greek έναργής ("distinct"), in reference to its distinct cleavage.

Enargite is related to lazarevicite (named after M. Lazarevic), which has the same chemical formula, but cubic crystalline structure.