Pale pink yellowish crystals of the very rare ammonium silicofluoride mineral bararite from one of the few known localities worldwide (Shamokin, Northumberland County, Pennsylvania, United States of America). — Photo: David Hospital · CC BY-SA 4.0
Bararite
The natural form of ammonium fluorosilicate — a trigonal salt-like mineral once classed under cryptohalite.
Intro adapted from Wikipedia (CC BY-SA).
Bararite is an IMA-recognized mineral species in the halide class, with the chemical formula (NH₄)₂SiF₆.
It crystallizes in the hexagonal crystal system (space group R-3m).
Key properties: Mohs hardness 2.5; specific gravity 2.152; Vitreous luster; optically uniaxial.
IMA symbol Brr, grandfathered status — known before the IMA’s founding, named in 1951.
Above a burning coal seam (Barari, India); a sublimation product at fumaroles (Vesuvius, Italy); a sublimation product in burning anthracite piles (Pennsylvania, USA).
It is found associated with Cryptohalite, sal ammoniac, sulfur.
The name refers to the occurrence at Barari, India, from which it was first characterized.