Enargite

Typically found as dark-grey to black massive material; crystals usually thick tabular, but may also be prismatic. May contain minor Sb (Springer, 1969). The most Sb-rich enargite was found to have the composition Cu3As0.8Sb0.2S4 (Pósfai & Buseck, 1998). Note: The synthetic system Cu^3As^xSb^1^-^xS^4 has a two phase region at x = 0.8. Mixtures with x < 0.8 crystallize in the famatinite type, compositions with x > 0.8 crystallize in the enargite type (Pfitzner & Bernert, 2004). Chemically similar to tennantite which, however, has no cleavage.

History

Activities related to discovery and approval of the group members

Structural context

Enargite
Crystal System orthorhombicCrystal Class orthorhombic pyramidalSpace Group Pmn21
a6.403—7.4262 (7.1464)
b6.162—7.43 (6.5881)
c3.687—6.18 (5.9321)
alpha90
beta90
gamma90
volume145.5—296.626 (280.3504)

Based on 11 measurements

Chemical context

Stoichiometric formulas

Enargite
mindat.org
  • March 13, 2023Cu3AsS4
IMA
  • March 13, 2023Cu3AsS4
mineralogy.rocks
  • Aug. 30, 2022Cu3AsS4

Elements recorded on EPMA

10
As
10
Cu
10
S
3
Sb

Physical properties

ColorColor entities, recognized using a custom trained NER model
  • greyish-black
  • grey/rose-brown
Color noteOriginal color note from the source
Greyish-black to black, grey/rose-brown in reflected light.
StreakStreak entities, recognized using a custom trained NER model
    Streak noteOriginal streak note from the source
    Black.
    Lustre
    Metallic
    Fracture
    Irregular/Uneven
    Transparency
    Opaque
    Tenacity
    brittle
    Hardness
    3
    Measured density
    4.4—4.5
    Calculated density
    4.4