STORY BY MARK LEATHERMAN
The distinction of one of the toughest copper minerals to find probably belongs to covellite, with dioptase serving as solid competition on that front. Like its more common cousins of chalcopyrite and bornite, covellite (also known as covelline) can display an unrivaled iridescence of dazzling colors usually in the realm of indigo, purple, and dark red hence its nicknames of “blue copper” and “indigo copper,” to name a few.
I, as well as at least a few others, have called it the most beautiful sulfide we have ever seen. Additionally, it is much softer than any of its copper-bearing cousins with a Mohs’ hardness of only 1.5 to 2. Speaking of common, an initial glance at its chemical formula (CuS) might not spark great conversation, but covellite’s constitution is more than skin deep.