White crystals of the rare ammonium sulphate mineral letovicite from Anna Mine (Anna 2 Mine, Aachen, North Rhine - Westphalia, Germany). Letovicite is one of the few minerals that are a mixture between an organic (NH4) and an inorganic (SO4) mineral. — Photo: David Hospital · CC BY-SA 4.0
Letovicite
A rare ammonium hydrogen sulfate formed on burning coal-waste heaps and at hot springs.
Intro adapted from Wikipedia (CC BY-SA).
Letovicite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (NH₄)₃H(SO₄)₂.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: specific gravity 1.83; optically biaxial.
IMA symbol Let, grandfathered status — known before the IMA’s founding, named in 1932.
A rare secondary mineral, formed from burning coal (Czech Republic); deposited from hot springs (The Geysers, California, USA).
It is found associated with Sulfur (Letovice, Czech Republic); mascagnite, boussingaultite (The Geysers, California, USA).
The name refers to Letovice, Czech Republic, the locality first noted for the mineral.