CuS with: High-temp-covellite — same chemistry, different crystal structure.Hexagonal
Covellite is a copper sulfide famous for its electric indigo-blue color and brilliant peacock iridescent tarnish — easily one of the most chromatically distinctive sulfides in nature. It is a common secondary mineral in the supergene-enriched zones of copper deposits.
Occurrence in China
Covellite is widespread in oxidized zones of Dexing (Jiangxi), Tonglushan (Hubei) and Pulang/Lanping (Yunnan) Cu deposits. The world’s largest crystals come from Butte (Montana), where covellite tabular plates reached several centimeters. Calabona (Sardinia) is the historic European source.
Identification
Indigo-blue + iridescent peacock tarnish + perfect basal cleavage producing flexible thin sheets + extreme softness. Distinguish from chalcocite (lead-gray, no iridescence) and bornite (which also tarnishes peacock but is purple-gold from fresh bronze and is harder).
Collector Notes
Butte covellite tablets remain the species archetype. Italian and Sardinian specimens with intense iridescence on quartz are also classic. Care: easily abraded due to softness.