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Formula: Cu3AsS4
Sulpharsenate of copper,
paramorph
of luzonite
Crystal System: Orthorhombic
Specific gravity: 4.4 to 4.5 measured, 4.40 calculated
Hardness: 3½
Streak: Black
Colour: Steel grey to iron black
Solubility: Slightly soluble in nitric acid
Common impurities: Sb,Fe,Pb,Zn,Ag,Ge
Environments:
Enargite is a comparatively rare mineral, found in vein and replacement deposits formed at moderate
temperatures
associated with pyrite,
sphalerite,
bornite,
galena,
tetrahedrite-tennantite,
covellite, chalcocite,
baryte and quartz
(Mindat, HOM).
Localities
At the Pingüino deposit, Tres Cerros, Deseado Department, Santa Cruz Province, Argentina, minor late grains
(<50 microns in size) of enargite are present in the cleavage planes of
galena or as irregular masses related to
freibergite
(CM 49.931-946).
At Lahóca Hill, Recsk, Pétervására District, Heves County, Hungary, enargite and
luzonite occur together in the
metasomatised ore bodies
(AM 83.365-372).
Enargite from Lahóca Hill - Image
The type locality is the San Francisco vein, Morococha District, Yauli Province, Junín, Peru.
Enargite from the San Francisco vein -
Image
At the Gregory mine, Ashover, Derbyshire, England, UK, enargite has been found with
calcite
(RES p103).
At the Ladywash mine, Eyam, Derbyshire Dales District, Derbyshire, England, UK, enargite occurs as metallic
grey-black crystals up to about 0.75 mm on edge, with chalcopyrite,
galena, pyrite and
sphalerite on a fluorite
specimen from the workings on Hucklow Edge Vein. The enargite occurs as a late-stage
primary phase in low-temperature
fluorite-dominated hydrothermal vein mineralisation
(JRS 22.6-10).
At Tintic Mining District, Juab County, Utah, USA, enargite generally occurs as metallic masses in
quartz matrix; it has also been found as single crystals and crystal groups
in pockets of quartz crystals at many of the mines in the district.
The enargite occurs mainly in coarsely crystalline aggregates of iron-black colour and excellent prismatic
cleavage. Some of the individual grains may be 2 or 3 inches in length. Good but very small crystals were seen on
quartz in vugs in ore from the Eureka Hill mine. Enargite is
associated with baryte and
jasperoid, and much of it contains small grains of
pyrite and chalcopyrite. Good
crystals of enargite, up to 2.5 cm and resting on quartz, have been
found at the Tintic Standard mine. On both the upper and lower dumps at the North Star mine, enargite
crystals to about 0.5 mm occur on a quartz and
baryte matrix associated with
azurite, chrysocolla,
jarosite, kettnerite,
malachite, mixite,
pyrite, tetrahedrite and
tyrolite
(MinRec 55.2.198-201).
Enargite from Tintic - Image
Alteration
enargite and pyrite to
Fe-tennantite, chalcopyrite
and sulphur
4Cu3AsS4 + 4FeS2 → Cu10Fe2As4S13
+ 2CuFeS2
+ 7/2S2
(CM 28.725-738)
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