Schairerite
Schairerite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Na₂₁(SO₄)₇ClF₆.
It crystallizes in the hexagonal crystal system (space group P31m).
Key properties: Mohs hardness 3.5; specific gravity 2.61–2.62; Vitreous luster; optically uniaxial.
IMA symbol Shr, grandfathered status — known before the IMA’s founding, named in 1931.
Found in a playa lake deposit (Searles Lake, California, USA); in association with an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada).
It is found associated with Galeite, gaylussite, tychite, pirssonite, thénardite, northupite, trona, hanksite, calcite (Searles Lake, California, USA); pectolite, shortite, kogarkoite.
The mineral was named to honor Dr. John Frank Schairer (1904–1970), American physical chemist, Carnegie Geophysical Laboratory, Washington, D.C., USA, who studied the system Na2 SO4 −NaF−NaCl−H2O.