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 | |
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General | |
Category | Sulfate mineral |
Formula (repeating unit) | Na3(SO4)F |
IMA symbol | Kog[1] |
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 |
Identification | |
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 | [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]
References
- 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.
- Handbook of Mineralogy
- Mindat.org
- Webmineral data