Yellowish microcrystals of the rare ammonium sulphate mineral mohrite from a locality in France (Saint Etienne-de-Baigorry, Pyrénées-Atlantiques, Nouvelle-Aquitaine, France). Ex Vandenbroucke Museum collection from Waregem, Belgium — Photo: David Hospital · CC BY-SA 4.0
Mohrite
A rare ammonium-iron sulfate found in Tuscany's geothermal fields and on burning coal dumps.
Intro adapted from Wikipedia (CC BY-SA).
Mohrite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (NH₄)₂Fe²⁺(SO₄)₂·6H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/a). It is a member of the Picromerite structural group.
Key properties: specific gravity 1.8–1.86; Vitreous luster; optically biaxial.
IMA symbol Mhr, IMA status: approved, named in 1964.
Found in boriferous fumaroles and geysers.
The mineral was named to honor Karl Friedrich Mohr (1806–1879), German analytical chemist, for whom the synthetic compound has long been named.