Kogarkoite - Locality: Poudrette quarry (Demix quarry; Uni-Mix quarry; Desourdy quarry), Mont Saint-Hilaire, Rouville RCM, Montérégie, Québec, Canada - FOV 4.7 x 7.1 mm — Photo: Modris Baum · Public domain
Kogarkoite
A pale-blue sodium sulfate-fluoride — a natural antiperovskite — from alkaline igneous complexes.
Intro adapted from Wikipedia (CC BY-SA).
Kogarkoite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Na₃(SO₄)F.
It crystallizes in the hexagonal crystal system (space group P2_1/m).
Key properties: Mohs hardness 3.5; specific gravity 2.66; White streak; Vitreous to dull luster; refractive index 1.44; optically biaxial.
IMA symbol Kog, IMA status: approved, named in 1970.
A sublimate from steam around a hot spring (Hortense Hot Spring, Colorado, USA); in nepheline syenite pegmatite veins in a differentiated alkalic massif (Mt. Alluaiv, Kola Peninsula, Russia).
It is found associated with Burkeite, trona, halite, fluorite, calcite, phillipsite (Hortense Hot Spring, Colorado, USA); villiaumite, thermonatrite, sidorenkite, nepheline, feldspar.
The mineral was named to honor Liya Nikolaevna Kogarko (1936–), Russian geochemist and petrologist, investigator of alkaline rocks.