Chalcanthite

crystals of chalcanthite, crystals of limonite : Planet Mine (Planet Copper Mine ; New Planet Mine), Planet Mine group (New Planet Mine group ; Great Central Mi — Photo: Parent Géry · CC BY-SA 3.0

Chalcanthite

Also known as: Copper sulfate, Blue vitriol.

The vivid blue-green hydrated copper sulfate — water-soluble, and famous for growing large electric-blue crystals.

Intro adapted from Wikipedia (CC BY-SA).

Chalcanthite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Cu(SO₄)·5H₂O.

It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Chalcanthite structural group.

Key properties: Mohs hardness 2.5; specific gravity 2.286; typically blue; White streak; Vitreous to resinous luster; refractive index 1.531; optically biaxial.

IMA symbol Cct, grandfathered status — known before the IMA’s founding.

Found as a secondary mineral in the oxidized portions of copper sulfide deposits, commonly of post-mining formation; rarely as a fumarolic deposit.

It is found associated with Melanterite, fibroferrite, rhomboclase, epsomite, goslarite, pickeringite, retgersite, morenosite, brochantite, gypsum.

The name comes from an older Latin name, chalcanthum, for flowers of copper.

Collections: Collector Favorites, Rare & Remarkable.