Covellite

Covellite is a copper sulfide mineral (CuS) instantly recognizable for its rich indigo-blue color combined with iridescent flashes of purple, bronze, and gold. It is one of the most distinctive blue minerals in the mineral kingdom.

It typically occurs as platy, foliated, or massive aggregates, and more rarely as thin hexagonal flakes with a metallic to submetallic luster. It is very soft and flexible in thin plates.

Though not a major ore by quantity, covellite is an interesting secondary copper mineral and a favorite of collectors for its remarkable play of color.

Covellite is chiefly a secondary mineral, forming in the supergene enrichment zones of copper deposits where primary copper sulfides such as chalcopyrite, bornite, and chalcocite are altered by descending, copper-rich waters.

It can also form directly around volcanic fumaroles as a sublimate, and occasionally as a primary mineral in some hydrothermal veins.

It is commonly associated with chalcocite, bornite, pyrite, and enargite. Notable localities include Butte, Montana (famous for fine crystals), Sardinia in Italy, Bor in Serbia, and copper districts in Alaska and Chile.

Look for an intensely indigo-blue mineral with a metallic to submetallic luster and striking iridescent purple-to-gold tarnish, often as platy or foliated masses. The blue color deepens and flashes when wetted.

It is extremely soft (1.5-2), easily scratched by a fingernail, and thin plates are flexible. The streak is dark gray to black.

Look-alikes are few because of the diagnostic blue color, but bornite shows more reddish-purple iridescence and is harder, and chalcocite is gray. The combination of indigo-blue color, extreme softness, platy habit, and iridescence is essentially unique to covellite.

Covellite is a minor ore of copper where it occurs in quantity, contributing to the metal used in electrical, plumbing, and alloy applications. It is not abundant enough to be a primary ore on its own.

Its chief value is to mineral collectors, who prize crystalline and richly iridescent specimens, especially classic pieces from Butte, Montana. Because it is soft and fragile it is rarely used in jewelry, though occasional stabilized cabochons appear.

Metaphysically it is linked to intuition and communication, though such claims are not scientific. Its true significance lies in mineralogy and the collecting world.