Vyacheslavite
Chemical formula: U<sup>4+</sup>(PO<sub>4</sub>)(OH)
Vyacheslavite is a rare, highly radioactive uranium mineral, found as microscopic, green crystals in the oxidation zones of uranium deposits.
Properties
- Mohs hardness
- 2-3
- Luster
- Vitreous
- Streak
- Light green
- Density
- 4.96
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Key diagnostic features of vyacheslavite are its intense green color, characteristic forms of small, tabular crystals forming rosette-like aggregates, and strong radioactivity. It occurs in the typical environment of oxidation zones of uranium deposits. ## Distinguishing from Similar Minerals Vyacheslavite can be confused with other green secondary uranium minerals, such as torbernite, metatorbernite, or autunite. Distinguishing it requires advanced research methods, such as X-ray diffraction (XRD), due to visual similarity and co-occurrence in the same localities. Reaction to UV radiation can be helpful – vyacheslavite does not fluoresce, unlike autunite. ## Crystal Forms Crystals are very small, usually tabular or platy, flattened parallel to {010}. They often form radial or rosette-like aggregates, as well as thin coatings and crusts on the surface of the host rock.
Geological environment
## Genesis Vyacheslavite is a secondary uranium mineral, formed in the oxidation zones of hydrothermal uranium-molybdenum deposits. It crystallizes under low-temperature conditions from solutions rich in uranium and phosphates. ## Mineral Associations This mineral co-occurs with other uranium minerals and sulfides. It is most commonly associated with uraninite, ningyoite, lermontovite, phosphouranylite, gypsum, calcite, pyrite, and molybdenite. ## Localities As a very rare mineral, vyacheslavite has been identified in only a few places worldwide. The type locality, where it was discovered, is a uranium-molybdenum deposit at an unspecified location in Russia. Its occurrence has also been confirmed at the Rabejac uranium mine in the Hérault department, France, and in the Lake Michigamme area in Quebec, Canada.
Rarity
Very rare
For collectors
## Quality Criteria For collectors, the quality and development of crystals are most important, despite their microscopic size. Specimens with clearly formed, rosette-like aggregates of intense, emerald-green color, contrasting with lighter host rock, are most prized. Due to the small size of the crystals, specimens are usually evaluated as a whole, and the abundance of the mineral on the matrix significantly increases their value. ## Popular Localities The most well-known specimens, though still extremely rare on the collector's market, come from the Rabejac mine in France. Material from the type locality in Russia is practically unavailable.
Care and storage
## Cleaning Vyacheslavite specimens should generally not be cleaned mechanically or chemically due to their delicacy and radioactivity. Any contaminants are best left undisturbed. If cleaning is absolutely necessary, compressed air can be used to remove loose dust, doing so with the utmost care to avoid inhaling potentially radioactive particles. ## What to Avoid Contact with water and chemicals must be strictly avoided. The mineral is sensitive to changes in humidity and temperature. It should not be heated or exposed to direct sunlight. The greatest danger is its radioactivity – direct skin contact should be avoided, and inhaling dust is particularly hazardous. ## Storage Vyacheslavite specimens must be stored in specialized, sealed containers, preferably with lead lining, to minimize radiation emission. The container should be clearly marked with the international radioactivity symbol. It should be kept away from areas of permanent human presence, as well as from other minerals that could be damaged by radiation.