General Information:
Chemical Formula:
(Ag,Cu)2S
Composition:
(Molecular Weight = 225.64 gm)
Copper 14.08 % Cu
Silver 71.71 % Ag
Sulfur 14.21 % S
Empirical Formula:
Ag1.5Cu0.5S
Environment:
Low temperature mineral in silver deposits.
IMA Status:
Approved IMA 1966
Locality:
Foster mine, Cobalt, Ontario, Canada.
Name Origin:
Named for Hugh E. McKinstry (1896-1961), U. S. Economic geologist.
Physical Properties:
Cleavage:
[???] Indistinct
Color:
dark gray, black, or steel gray.
Density:
6.61
Diaphaniety:
Opaque
Habits:
Microscopic Crystals - Crystals visible only with microscopes., Granular - Generally occurs as anhedral to subhedral crystals in matrix., Aggregates - Made of numerous individual crys tals or clusters.
Hardness:
1.5-2.5 - Hardness very near Gypsum
Luster:
Metallic
Streak:
dark gray
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