Bokite

Chemical formula: (Al,Fe<sup>3+</sup>)<sub>1.3</sub>(V<sup>5+</sup>,V<sup>4+</sup>,Fe<sup>3+</sup>)<sub>8</sub>O<sub>20</sub>·7.5H<sub>2</sub>O

Bokite is a rare oxovanadate mineral with a complex chemical composition, forming microscopic, acicular crystals of dark brown to black color.

## Characteristics Bokite is a very rare, hydrated aluminum and iron oxovanadate, belonging to the vanadium oxide group. It occurs as microscopic, acicular or bladed crystals, which often form radial or tangled aggregates, as well as crusts and coatings. Its color is typically dark brown to almost black, which, combined with the small size of the crystals, makes it difficult to identify with the naked eye. ## Physical Properties Bokite crystals exhibit a luster described as metallic to submetallic. The hardness on the Mohs scale is approximately 3. The mineral is opaque. Due to its microscopic nature, many of its physical properties, such as density or fracture, have not been precisely determined. ## History and Name The mineral's name comes from the Soviet crystallographer and geochemist, Georgy Borisovich Bokii (1909–2001), in recognition of his contribution to mineralogy. Bokite was first described in 1961 by E.A. Ankinovich and others based on material found in Kazakhstan. ## Uses Bokite has no industrial application. Its significance is purely scientific and collectible, as a very rare and unusual vanadium mineral.

Properties

Mohs hardness
3
Luster
Metallic
Streak
Brown
Cleavage
Perfect on {001}
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Amateur identification of bokite is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS) to confirm its composition and structure. Visually, it might be suspected as black, acicular aggregates in association with other rare vanadates. ## Distinguishing from similar minerals Bokite can be confused with other black, acicular vanadium minerals, such as kazakhstanite, with which it often co-occurs. Differentiation requires specialized laboratory analysis. ## Crystal forms Bokite forms very fine, acicular or bladed crystals, elongated along the [010] axis. These crystals combine into radial, tangled, or fibrous aggregates, and also form thin crusts on host rocks.

Geological environment

## Genesis Bokite is a secondary mineral, formed in the oxidation zones of polymetallic deposits hosted in black carbonaceous-siliceous shales. It forms as a result of the weathering of primary vanadium minerals under low-temperature conditions. ## Mineral associations This mineral co-occurs with other rare vanadium minerals, such as kazakhstanite, satpaevite, alvanite, as well as with quartz, calcite, gypsum, and clay minerals. ## Localities The most important and classic localities for bokite are in Kazakhstan, particularly in the Kara-Tau vanadium deposits (e.g., Balasauskandyk and Kurumsak deposits). These are the only confirmed locations from which well-studied specimens of this mineral originate.

Rarity

Very rare

For collectors

## Quality criteria The quality of bokite specimens is primarily assessed based on the richness and visibility of crystalline aggregates on the rock matrix. Since the crystals are microscopic, specimens with extensive and well-formed crusts are most valued. Association with other rare vanadium minerals is also important, as it increases the scientific and collectible value of the specimen. ## Popular localities The only source of collectible bokite specimens is the vanadium deposits in the Kara-Tau mountains in southern Kazakhstan. Specimens from other localities are not known on the market.

Care and storage

## Cleaning Bokite specimens are extremely delicate due to their microscopic and acicular crystals. Mechanical cleaning is highly inadvisable. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust. Avoid contact with water and any chemicals. ## What to avoid Ultrasonics, steam cleaners, acids, solvents, and detergents must be strictly avoided. The mineral is sensitive to shocks and abrasions, which can destroy the fine crystals. Store away from moisture and sudden temperature changes. ## Storage Bokite specimens should be stored in stable conditions, preferably in a closed "micromount" box, to protect them from dust, mechanical damage, and moisture. Avoid exposure to direct sunlight.

Sources

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