Kogarkoite
Chemical formula: Na<sub>3</sub>S<sup>6+</sup>O<sub>4</sub>F
Kogarkoite is a rare sodium fluorosulfate, forming colorless or white coatings and crusts near volcanic fumaroles or in alkaline pegmatites.
Properties
- Mohs hardness
- 3.5
- Luster
- Vitreous
- Streak
- White
- Density
- 2.67-2.68
- Cleavage
- Perfect on {001}, good on {110}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification A key diagnostic feature of kogarkoite is its water solubility (destructive test). Many specimens exhibit creamy white or white fluorescence under ultraviolet light (both longwave and shortwave). Occurrence in a fumarolic environment or within ultra-alkaline pegmatites is a strong indicator. ## Differentiation from Similar Minerals Kogarkoite is sometimes confused with other white, soluble minerals from fumarolic and evaporitic parageneses. It differs from halite (salty taste, regular crystallographic system) by its lack of taste and different symmetry. It differs from thenardite (Na₂SO₄) by the presence of fluorine in its composition, fluorescence, and monoclinic crystallographic system (thenardite is orthorhombic). It differs from trona by its lack of reaction with acids. ## Crystal Forms Kogarkoite forms small, tabular or prismatic crystals, often grouped into rosette-like or radial aggregates. However, it is most commonly found as fine-grained or powdery coatings and crusts.
Geological environment
## Genesis Kogarkoite forms in two ways. It was originally discovered as a product of sublimation (resublimation) of volcanic gases in exhalations and fumaroles at temperatures above 100°C. The second important environment for its occurrence is highly alkaline pegmatites within nepheline syenite massifs, where it crystallizes in the late stages of hydrothermal processes. ## Mineral Associations In fumarolic paragenesis, it co-occurs with halite, trona, and thermonatrite. In alkaline pegmatites (e.g., on the Kola Peninsula), it is accompanied by minerals such as villiaumite, aegirine, lomonosovite, natrosilite, and rasvumite. ## Localities The most important localities for this mineral are the Khibiny and Lovozero massifs on the Kola Peninsula in Russia, the Ilímaussaq complex in Greenland, and Mont Saint-Hilaire in Canada. It also occurs in the Vesuvius volcano region in Italy, on the Ol Doinyo Lengai volcano in Tanzania, and at the type locality in Colorado, USA.
Rarity
Rare
For collectors
## Quality Criteria Specimens with well-formed, transparent crystals with visible luster are most highly valued by collectors. Crystal groups on a contrasting matrix, such as dark aegirine, are particularly attractive. The size and clarity of the crystals are key factors influencing the value of a specimen. Specimens from classic, rare localities are also more sought after. ## Popular Localities Mont Saint-Hilaire in Canada and the alkaline massifs of the Kola Peninsula in Russia are considered the best sources of well-formed kogarkoite crystals. Specimens from these localities fetch the highest prices and are most desirable in systematic collections.
Care and storage
## Cleaning The mineral is water-soluble, therefore **it must absolutely not be cleaned with water**. To remove dust, only a soft, dry brush or low-pressure compressed air should be used. ## What to Avoid Avoid contact with water, water vapor, and any chemical solutions. Kogarkoite is sensitive to moisture, so it should be protected from high humidity and sudden temperature changes, which could lead to water vapor condensation on the specimen's surface. ## Storage Kogarkoite specimens require storage in dry conditions. It is recommended to keep them in airtight containers (e.g., "membrane box" type) or in sealed display cases with a desiccant (e.g., silica gel).