| Kogarkoite | |
| Category: | Sulfate mineral |
| Formula: | Na3(SO4)F |
| Imasymbol: | Kog[1] |
| Strunz: | 7.BD.15 |
| System: | Monoclinic |
| Class: | Pyramidal (2/m) (same H-M symbol) |
| Symmetry: | 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 |
| Habit: | Tabular crystals, granular, earthy aggregates, pseudorhombohedral |
| Twinning: | Common |
| Mohs: | 3.5 |
| Luster: | Vitreous to dull |
| Streak: | White |
| Diaphaneity: | Transparent to translucent |
| Gravity: | 2.66 |
| Opticalprop: | Biaxial (+) |
| Refractive: | nα = 1.439 nβ = 1.439 nγ = 1.442 |
| Birefringence: | δ = 0.003 |
| 2V: | Small, approaching zero |
| Fluorescence: | Cream to pale blue under SW UV and green under LW UV |
| Solubility: | Slowly soluble in water |
| References: | [2] [3] [4] |
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 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]