Chuquicamata, Chile — Photo: Pacific Museum of Earth from Canada · CC BY-SA 2.0
Ferrinatrite
Ferrinatrite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Na₃Fe³⁺(SO₄)₃·3H₂O.
It crystallizes in the hexagonal crystal system (space group P-3).
Key properties: Mohs hardness 2.5; specific gravity 2.55–2.61; Vitreous luster; optically uniaxial.
IMA symbol Fnat, grandfathered status — known before the IMA’s founding, named in 1889.
An oxidation product of iron sulfides, typically in arid regions; rarely fumarolic.
It is found associated with Metavoltine, copiapite, coquimbite, sideronatrite, tamarugite, quenstedtite, römerite (Chile); gypsum, sideronatrite, metavoltine, tamarugite, uklonskovite.
The name refers to its essential chemical components: FERRIc iron and sodium, NATRium.