Many whitish crystal aggregates of the rare Cu mineral chalcocyanite from the type locality in Mount Vesuvius, Italy in a capsule. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Chalcocyanite
Chalcocyanite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Cu(SO₄).
It crystallizes in the orthorhombic crystal system (space group Pnma). It is a member of the Zinkosite structural group.
Key properties: Mohs hardness 3.5; specific gravity 3.65; optically biaxial.
IMA symbol Ccy, grandfathered status — known before the IMA’s founding, named in 1873.
Occurs as sublimates near volcanic fumaroles.
It is found associated with Dolerophanite, melanothallite, eriochalcite, euchlorine (Vesuvius, Italy); euchlorine, eriochalcite, dolerophanite, melanothallite, piypite, ponomarevite.
Its name comes from the Greek for copper and azure-blue, in allusion to the composition and color change caused by hydration.