DIGENITE
Digenite is a scarce copper sulfide mineral, Cu9S5.
It has a metallic luster, dark bluish-gray to blackish color, dark gray
streak, and a Mohs hardness of 2.5 to 3. It’s usually massive, but can
form pseudocubic crystals. Broken surfaces show conchoidal
fracture. Primary digenite occurs in some copper-bearing hydrothermal
veins, some intrusive igneous rocks, and in some sulfide exhalative deposits.
Digenite-rich
hydrothermal vein sample (2.25 cm across along the base) from the Leonard Mine
at Butte, southwestern Montana, USA. In this area, digenite occurs in 62
to 66 million year old copper sulfide-rich hydrothermal veins that intrude the
Butte Quartz Monzonite, a pluton of the Boulder Batholith (mid-Campanian Stage,
late Late Cretaceous, 76 million years).