Römerite
Römerite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Fe²⁺Fe³⁺₂(SO₄)₄·14H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Römerite structural group.
Key properties: Mohs hardness 3–3.5; specific gravity 2.174; Oily, resinous, vitreous luster; optically biaxial.
IMA symbol Röm, grandfathered status — known before the IMA’s founding, named in 1858.
Occurs as an early alteration product of oxidizing pyrite or pyrrhotite; uncommonly a volcanic sublimate.
It is found associated with Copiapite, melanterite, voltaite, halotrichite, szomolnokite, kornelite, rozenite, siderotil, alunite.
The mineral was named to honor Friedrich Adolph Römer (1809–1869), German geologist, Director of the School of Mines, Clausthal, Germany.