Yellow magnesiocopiapite crystals from United Verde Extension Mine, Jerome, Yavapai County, Arizona, United States of America. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Magnesiocopiapite
Magnesiocopiapite is an IMA-recognized mineral species in the sulfate class, with the chemical formula MgFe³⁺₄(SO₄)₆(OH)₂·20H₂O.
It crystallizes in the triclinic crystal system (space group P1). It is a member of the Copiapite structural group.
Key properties: Mohs hardness 2–3; specific gravity 2.16; optically biaxial.
IMA symbol Mcpi, grandfathered status — known before the IMA’s founding, named in 1938.
An uncommon secondary mineral, typically produced through oxidation of pyrite.
It is found associated with Pyrite, römerite, paracoquimbite, halotrichite, redingtonite.
The name refers to its magnesium content and relation to copiapite.