Vysokýite
Chemical formula: U⁴⁺[As⁵⁺O₂(OH)₂]₄·4H₂O
Vysokýite is an extremely rare, secondary uranyl mineral, forming microscopic, yellowish-green tabular crystals.
Properties
- Mohs hardness
- 2
- Color
- Light-green
- Luster
- Vitreous
- Streak
- Greenish-gray to grayish
- Density
- 3.393
- Cleavage
- along (100) and (001)
- Fracture
- Irregular/Uneven
- Transparency
- Transparent to Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification Field identification of vysokýite is practically impossible. It requires advanced laboratory methods, such as X-ray diffraction (XRD) and chemical spectroscopy (EDS/WDS), due to its microscopic size and co-occurrence with other secondary uranium minerals. The characteristic yellowish-green color and radial aggregates of tabular crystals are an indication, but not a diagnostic feature. ## Distinguishing from Similar Minerals It can be confused with many other secondary uranyl arsenates, such as zeunerite, metazeunerite, kahlerite, or nováčekite, which have similar colors and often occur in the same localities. Definitive differentiation is only possible through X-ray analysis. ## Crystal Forms Crystals are very small, usually measuring up to 0.2 x 0.05 x 0.01 mm. They have the form of thin tablets or blades, often flattened. They form characteristic radial or spherical aggregates, as well as thin coatings.
Geological environment
## Genesis Vysokýite is a secondary mineral, formed in the oxidation zones of uranium-arsenic deposits. It forms as a result of weathering and alteration of primary uranium minerals (mainly uraninite) and arsenic in the presence of water. ## Mineral Associations It co-occurs with other secondary uranium minerals. In the type locality, it was found in association with gypsum, zeunerite, metazeunerite, arsenuranospathite, and other unidentified uranyl arsenates. ## Localities The only confirmed and described locality of vysokýite occurrence in the world is the waste dump of the Geschieber mine in Jáchymov (Krušné hory, Czech Republic).
Rarity
Extremely rare
For collectors
## Quality Criteria As a microscopic mineral, the quality of a specimen is primarily determined by the richness and development of crystal aggregates visible under magnification. Samples with clearly formed, radial groups of crystals, contrasting with the rock matrix, are most valued. The certainty of identification, confirmed by a reliable source or analysis, is also important. ## Popular Localities The only source of specimens is the type locality - Jáchymov in the Czech Republic. Material from this location is extremely rare and sought after by specialized collectors of micromounts and uranium minerals.
Care and storage
## Cleaning Due to the extreme delicacy and microscopic size of the crystals, mechanical cleaning is inadvisable and can lead to the destruction of the specimen. Contact with water and any chemicals should be avoided. ## What to Avoid The mineral is sensitive to changes in humidity and temperature. As a secondary mineral, it can undergo dehydration or recrystallization under inappropriate conditions. Contact with acids and other chemical agents must be strictly avoided. Due to high radioactivity, exposure should be limited, and hands should always be washed after handling the specimen. ## Storage Specimens should be stored under stable conditions, in closed, sealed containers (e.g., "micromount" type), to protect them from dust, mechanical damage, and humidity changes. Store away from other minerals that may be sensitive to radiation. It is essential to clearly label the container as radioactive material.