Eriochalcite Locality: Tolbachik volcano, Kamchatka Oblast', Far-Eastern Region, Russia Light green balls of Eriochalcite, field of view 3 mm. Specimen and photo Leon Hupperichs. — Photo: Leon Hupperichs · CC BY-SA 3.0
Eriochalcite
Natural copper(II) chloride dihydrate — the blue-green hydrated mineral of oxidized copper deposits.
Intro adapted from Wikipedia (CC BY-SA).
Eriochalcite is an IMA-recognized mineral species in the halide class, with the chemical formula CuCl₂·2H₂O.
It crystallizes in the orthorhombic crystal system (space group Pbmn).
Key properties: Mohs hardness 2.5; specific gravity 2.4; Vitreous luster; optically biaxial.
IMA symbol Ech, grandfathered status — known before the IMA’s founding, named in 1870.
Occurs as an encrustation around fumaroles (Vesuvius, Italy); a product of weathering in a copper sulfide deposit in an arid climate (Quetena, Chile).
It is found associated with Melanothallite, euchlorine, chalcocyanite, dolerophanite (Vesuvius, Italy); atacamite, bandylite (Quetena, Chile); euchlorine, chalcocyanite, dolerophanite.
Its name comes from the Greek for wool and copper, for the form of aggregates at Vesuvius, Italy.