Oxy-vanadium-dravite

Chemical formula: NaV₃+₃(V₃+₄Mg₂)(Si₆O₁₈)(BO₃)₃(OH)₃O

Oxy-vanadium-dravite is an extremely rare mineral from the tourmaline group, distinguished by the dominance of vanadium and oxygen in its structure.

## Characteristics Oxy-vanadium-dravite is a member of the tourmaline group, defined as a species in which vanadium (V³⁺) is the dominant element in the Y site, and oxygen (O²⁻) dominates over the hydroxyl group (OH⁻) in the O(3) site. This mineral forms poorly developed, prismatic crystals up to 1.5 mm long, often occurring in aggregates. Its black color and vitreous luster are typical of many tourmalines. ## Physical Properties Oxy-vanadium-dravite is characterized by a hardness of 7.5 on the Mohs scale, which is typical for tourmalines. It has a vitreous luster and is opaque. Its calculated density is approximately 3.35 g/cm³. It exhibits no cleavage, and its fracture is uneven. ## Colors and Varieties This mineral occurs in a uniform, black color. Due to its extreme rarity, no color varieties or commercial forms have been distinguished. ## History and Name Oxy-vanadium-dravite was first described in 2013 by a team of mineralogists (A. Ertl et al.) based on material from Perevaly in the Sludyanka area near Lake Baikal in Russia. Its name refers to its chemical composition – indicating the dominance of oxygen (Oxy) and vanadium, and its structural relationship to dravite, another mineral from the tourmaline group.

Properties

Mohs hardness: 7.5
Luster: Vitreous
Streak: Gray
Density: 3.35
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Identification of oxy-vanadium-dravite is impossible without advanced analytical techniques, such as electron spectroscopy (EDS/WDS) or X-ray diffraction (XRD). In field conditions or in a collection, it is indistinguishable from other black tourmalines, such as schorl or dravite. ## Distinguishing from Similar Minerals It can be confused with black schorl, dravite, buergerite, or povondraite. The key distinguishing feature is the dominance of vanadium in its chemical composition, which requires specialized analysis. Visually, it is practically identical to other black, prismatic tourmalines. ## Crystal Forms It forms poorly developed, prismatic crystals with a triangular cross-section, terminated by a trigonal pyramid. It occurs as single crystals or small aggregates.

Geological environment

## Genesis Oxy-vanadium-dravite forms in metamorphic rocks. In its type locality (Perevala, Russia), it was found in calcite-diopside marbles that underwent metamorphism under amphibolite facies conditions. ## Mineral Associations This mineral co-occurs with calcite, diopside, quartz, phlogopite, tremolite, titanite, pyrite, and other minerals from the tourmaline group, such as vanado-oxy-dravite. ## Localities The only confirmed locality of oxy-vanadium-dravite in the world is its type locality: Perevala marble quarry, Sludyanka area, Irkutsk Oblast, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of an oxy-vanadium-dravite specimen is primarily assessed based on the degree of crystal development and their size. Well-formed, prismatic crystals are most desired, even if small. Association with other minerals, forming an aesthetic composition on the rock matrix, is also crucial. Confirmation of identification through chemical analysis significantly increases the specimen's value.

Care and storage

## Cleaning It is recommended to clean only with a soft, dry brush to remove dust. Due to its extreme rarity and scientific value, all invasive methods should be avoided. The use of water, especially ultrasonics, is discouraged without consulting an expert. ## What to Avoid Avoid contact with chemicals, acids, and detergents. The mineral should be protected from sudden temperature changes and prolonged exposure to strong light, although its sensitivity to UV radiation is not known. ## Storage Specimens should be stored in stable conditions, preferably in a sealed display box, to protect them from dust, mechanical damage, and moisture. Due to the small size of the crystals, small "micromount" type boxes are ideal.

Sources

IMA Mineral List (CNMNC)