COVELLITE
Covellite is an attractive, deep metallic blue mineral
having the formula CuS - copper sulfide. It's principally a secondary
sulfide mineral, formed by the breakdown of pre-existing copper-bearing
sulfides, but also occurs in a massive or crystalline form as a primary mineral.
Covellite has a metallic luster, an intensely deep blue or purplish blue color,
a dark gray streak, and is quite soft (H = 1.5 to 2). Well-formed
crystals are hexagonal plates with a somewhat micaceous appearance.
Covellite (1.9 cm across along the base) from the Leonard Mine at Butte,
Montana, USA. Butte covellite occurs in copper sulfide-rich hydrothermal
veins (62-66 million years, latest Cretaceous to Early Paleocene) that intrude
the Butte Quartz Monzonite (mid-Campanian Stage, late Late Cretaceous, 76
million years).
Covellite (1.4 cm across) from the Leonard Mine at Butte, Montana, USA.
Butte covellite occurs in copper sulfide-rich hydrothermal veins (62-66 million
years, latest Cretaceous to Early Paleocene) that intrude the Butte Quartz
Monzonite (mid-Campanian Stage, late Late Cretaceous, 76 million years).
Covellite-pyrite hydrothermal vein (4.1 cm across at its widest) from the Butte Mining
District, southwestern Montana, USA (same geology as specimens shown above).