Koksharovite
Chemical formula: CaMg₂Fe³⁺₄(V⁵⁺O₄)₆
Koksharovite is a rare black vanadium mineral with a metallic luster, found in volcanic fumaroles.
Properties
- Mohs hardness
- 4.5
- Color
- Yellowish-brown to reddish-brown
- Luster
- Metallic
- Streak
- Yellowish-brown
- Density
- 3.39
- Cleavage
- Perfect on {0001}
- Fracture
- Irregular/Uneven
- Transparency
- Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification Identification of koksharovite is based on its unique occurrence environment (volcanic fumaroles), black color, metallic luster, and characteristic form of fine, tabular crystals. Macroscopic identification is practically impossible and requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), to confirm its chemical composition and crystal structure. ## Distinguishing from Similar Minerals At first glance, it may be confused with other black, microcrystalline minerals found in similar environments, such as some manganese or iron oxides. Definitive differentiation is possible only through chemical analysis, which will show the predominant presence of vanadium, calcium, magnesium, and iron. ## Crystal Forms Koksharovite forms very small, thin, tabular crystals with a hexagonal outline, reaching sizes up to 0.2 x 0.2 x 0.02 mm. These crystals often occur as radial aggregates or irregular clusters and coatings on rock surfaces.
Geological environment
## Genesis Koksharovite is a mineral of volcanic origin, formed by sublimation from volcanic gases in high-temperature fumaroles. It crystallizes directly from the gas phase at temperatures above 600°C on the surfaces of andesitic and basaltic rocks. ## Mineral Associations This mineral co-occurs with other products of volcanic exhalations, such as hematite, anhydrite, sylvite, halite, and also with other rare vanadates, e.g., shcherbinaite (V₂O₅). ## Localities The only confirmed occurrences of koksharovite in the world are the active fumaroles of Bezymianny volcano and Tolbachik volcano (2012-2013 eruption) on the Kamchatka Peninsula in Russia. These are its type localities.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of koksharovite specimens is primarily assessed based on the abundance and visibility of crystals on the rock matrix. The most valued specimens are those with clearly formed, though still microscopic, crystalline aggregates that contrast with a lighter substrate. Due to the nature of the mineral, the purity and size of individual crystals are not key criteria, as all known crystals are very small. ## Popular Localities The only source of collectible specimens is the fumaroles of Bezymianny and Tolbachik volcanoes in Kamchatka, Russia. Obtaining material from these locations is extremely difficult and dangerous, making each specimen unique.
Care and storage
## Cleaning Due to the extreme rarity and fragility of specimens, mechanical cleaning is absolutely inadvisable. Specimens should be protected from dust by storing them in sealed containers. If cleaning is necessary, compressed air can be used from a safe distance to remove loose particles. ## What to Avoid Avoid contact with water, acids, and other chemicals, as the mineral's reactivity is not fully understood. Protect it from ultrasound, high temperatures, and sudden thermal changes. Due to its occurrence in volcanic sublimation products, it may be unstable under conditions other than those in which it formed. ## Storage Koksharovite specimens should be stored in specialized, sealed "micromount" boxes that protect them from mechanical damage, dust, and moisture. Avoid exposure to sunlight and store in stable temperature conditions.