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Kogarkoite - Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada.jpg
Category Sulfate mineral
(repeating unit)
Strunz classification 7.BD.15
Crystal system Monoclinic
Crystal class Pyramidal (2/m)
(same H-M symbol)
Space group P21/m
Unit cell a = 18.07, b = 6.94
c = 11.44 [Å]; β = 107.72°; Z = 12
Color Colorless, pale sky-blue, pale pink, lilac
Crystal habit Tabular crystals, granular, earthy aggregates, pseudorhombohedral
Twinning Common
Mohs scale hardness 3.5
Luster Vitreous to dull
Streak White
Diaphaneity Transparent to translucent
Specific gravity 2.66
Optical properties Biaxial (+)
Refractive index nα = 1.439 nβ = 1.439 nγ = 1.442
Birefringence δ = 0.003
2V angle Small, approaching zero
Ultraviolet fluorescence Cream to pale blue under SW UV and green under LW UV
Solubility Slowly soluble in water
References [1][2][3]

Kogarkoite is a sodium sulfate fluoride mineral with formula Na3(SO4)F. It has a pale blue color. The specific gravity is about 2.67 and the hardness is 3.5. The crystal system is monoclinic. Kogarkoite is named after the Russian petrologist Lia Nikolaevna Kogarko (born 1936) who discovered the mineral.

Discovery and occurrence[edit]

Kogarkoite was first described in 1973 for an occurrence on Alluaiv Mountain, Lovozero Massif, Kola Peninsula, Russia.[2] On Alluaiv it occurs in pegmatitic veins in nepheline syenite. It occurs with sodalite in syenite xenoliths in an alkali intrusive complex at Mont Saint-Hilaire, Canada. In Hortense Hot Spring, Chaffee County, Colorado, it occurs as a sublimate.[1] It occurs at Lake Natron near Ol Doinyo Lengai, Tanzania and Suswa Volcano, Lake Magadi, Kenya.[1][2]

See also[edit]