Image: <bdi><a href="https://www.wikidata.org/wiki/Q56247090" class="extiw" title="d:Q56247090"><span title="mineral collector and dealer">Robert M. Lavinsky</span></a></bdi> (CC BY-SA 3.0)
orthorhombiccommonSulfides
Chalcocite
Cu₂S
This specimen shows a dark, lead-gray to black mass of chalcocite, often exhibiting a dull metallic luster and sometimes a bluish or greenish tarnish. It forms dense, fine-grained aggregates or pseudohexagonal crystals.
Chalcocite Physical Properties
Mohs Hardness
2.5Crystal System
orthorhombicLuster
metallicStreak Color
grayish blackCleavage
indistinct on {110}Fracture
conchoidalSpecific Gravity
5.7Colors
dark gray, lead-gray, black, often with blue or green tarnishTransparency
opaqueType Locality
St Ives Consols (incl. Wellesley Mine; Wheal Mary), St Ives, St Ives District, Cornwall, England, UKMineral Group
SulfidesUses
important copper oreAssociated Minerals
bornite, covellite, chalcopyrite, pyrite, native copper, quartz, calciteRarity
commonGeological Context
Chalcocite is a secondary copper sulfide mineral, commonly found in the supergene enrichment zones of copper deposits where primary copper sulfides are altered by weathering. It can also occur in hydrothermal veins.
