Kogarkoite

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

Kogarkoite
General
CategorySulfate mineral
Formula
(repeating unit)		Na3(SO4)F
IMA symbolKog[1]
Strunz classification7.BD.15
Crystal systemMonoclinic
Crystal classPyramidal (2/m)
(same H-M symbol)
Space groupP21/m
Unit cella = 18.07, b = 6.94
c = 11.44 [Å]; β = 107.72°; Z = 12
Identification
ColorColorless, pale sky-blue, pale pink, lilac
Crystal habitTabular crystals, granular, earthy aggregates, pseudorhombohedral
TwinningCommon
Mohs scale hardness3.5
LusterVitreous to dull
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity2.66
Optical propertiesBiaxial (+)
Refractive indexnα = 1.439 nβ = 1.439 nγ = 1.442
Birefringenceδ = 0.003
2V angleSmall, approaching zero
Ultraviolet fluorescenceCream to pale blue under SW UV and green under LW UV
SolubilitySlowly soluble in water
References[2][3][4]

Discovery and occurrence

Kogarkoite was first described in 1973 for an occurrence on Alluaiv Mountain, Lovozero Massif, Kola Peninsula, Russia.[3] 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.[2] It occurs at Lake Natron near Ol Doinyo Lengai, Tanzania and Suswa Volcano, Lake Magadi, Kenya.[2][3]

See also

References
  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. Handbook of Mineralogy
  3. Mindat.org
  4. Webmineral data


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