Aluminocopiapite Locality: Montcada hill quarry (Pedrera del Turó de Montcada), Montcada i Reixac, Vallès Occidental, Barcelona, Catalonia, Spain Dimensions: 4 cm x 2 cm x 1 cm Description: Orange botryoidal aggregates of flattened aluminocopiapite (analized by SEM-EDS) crystals. — Photo: Joan Rosell (RosellMinerals.com) · CC BY 3.0
Aluminocopiapite
An aluminium-iron sulfate whose type localities are Alaska's Fortymile River and Utah's San Rafael Swell.
Intro adapted from Wikipedia (CC BY-SA).
Aluminocopiapite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (Al,Mg)Fe³⁺₄(SO₄)₆(OH,O)₂·20H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Copiapite structural group.
Key properties: Mohs hardness 2–3; specific gravity 2.163; optically biaxial.
IMA symbol Acpi, grandfathered status — known before the IMA’s founding, named in 1947.
A secondary mineral typically formed by the oxidation of pyrite in shales and coal; may be a fumarolic reaction product.
It is found associated with Pyrite.
The name refers to its content of aluminum and relation to the copiapite group.