Covellite (also know as covelline) is a crystalline form of copper(II) sulfide (CuS). In appearance it is an enchanting indigo blue. It is associated with chalcosite in zones of secondary enrichment (supergene) of copper sulfide deposits. Commonly found with and as coatings on chalcocite, chalcopyrite, bornite, enargite , pyrite, and other sulfides. Often occurs as pseudomorphic replacements after other minerals. Very rare occurrence as a volcanic sublimate at Mount Vesuvius the site of its discovery or first description by N. Covelli (1790 - 1829).
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