Metallic inclusions of the extremely rare germanium mineral calvertite in a matrix of chalcosine and germanite in a completely analyzed sample by SEM/EDS. From Polkowice-Sieroszowice Mine, Polkowice, Lower Silesian Voivodeship, Poland. Ex Vandenbroucke Museum collection from Waregem, Belgium. Size: 0.2 × 0.1 × 0.1 cm — Photo: David Hospital · CC BY-SA 4.0
Calvertite
Calvertite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Cu₅Ge₀.₅S₄.
It crystallizes in the cubic crystal system.
Key properties: Mohs hardness 4–5; specific gravity 5.239; Black streak; Metallic. Birefringence: None luster.
IMA symbol Cvt, IMA status: approved, named in 2006.
Found in a highly oxidized, polymetallic, fractured and brecciated dolomite and sandstone pipe.
It is found associated with Reinerite, tennantite, gallite, chalcocite.
The mineral was named to honor Lauriston (Larry) Derwent Calvert (1924–1993) of the National Research Council, Ottawa.