Wyartite
Chemical formula: CaU<sup>5+</sup>(U<sup>6+</sup>O<sub>2</sub>)<sub>2</sub>(CO<sub>3</sub>)O<sub>4</sub>(OH)·7H<sub>2</sub>O
Wyartite is a rare, secondary uranium mineral with an intensely black color and a resinous luster, forming radial aggregates.
Properties
- Mohs hardness
- 3-4
- Luster
- Resinous
- Streak
- Black
- Density
- 5
- Cleavage
- Perfect on {001}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Wyartite is recognized by its characteristic black color, resinous to submetallic luster, and typical radial or spherulitic aggregates. A key diagnostic feature is its very strong radioactivity, easily detectable with a Geiger counter. ## Distinguishing from similar minerals It can be confused with other black, secondary uranium minerals, such as some varieties of uraninite (pitchblende) or other "black uranium oxides." However, wyartite is distinguished by its form of occurrence (radial aggregates), luster, and specific chemical composition, the verification of which requires advanced analytical methods. ## Crystal forms It forms microscopic tabular or platy crystals, which almost always occur in the form of radial, fibrous, or spherulitic aggregates. It is less commonly found as thin crusts.
Geological environment
## Genesis Wyartite is a secondary mineral, forming in the oxidation zones of uranium ore deposits. It forms as a result of weathering and alteration of primary uraninite in the presence of carbonate-rich solutions. Its formation is associated with relatively low temperatures. ## Mineral associations It most often co-occurs with other secondary uranium minerals, such as schoepite, becquerelite, curite, rutherfordine, as well as with primary uraninite. Associated minerals may also include calcite and dolomite. ## Localities The most important and classic locality for wyartite is the Shinkolobwe mine in Katanga Province, Democratic Republic of Congo. It is also known from several other localities worldwide, including the Krunkelbach mine in the Black Forest (Germany) and the Lake Athabasca region in Saskatchewan (Canada).
Rarity
Very rare
For collectors
## Quality criteria The most valued by collectors are specimens with well-formed, lustrous, radial aggregates of intense black color. Contrast with the host rock and the presence of associated minerals that confirm the paragenesis are important. The size of the aggregates and the richness of the specimen significantly affect its value. ## Popular localities By far the most desired and historically important specimens come from the type locality – the Shinkolobwe mine in the Democratic Republic of Congo. Material from this mine is considered the global standard for this mineral.
Care and storage
## Cleaning The mineral should not be wet cleaned. Any attempts at cleaning may lead to its damage or dissolution. Only gentle dust removal with a soft brush or compressed air from a safe distance is permissible. ## What to avoid Contact with water, acids, bases, and all chemical agents must be strictly avoided. The mineral is sensitive to changes in humidity and temperature. As a uranium mineral, it is highly radioactive – direct skin contact should be avoided, dust should not be inhaled, and hands should be washed after every contact. ## Storage Wyartite specimens must be stored in specialized, airtight containers (e.g., "perky box" type) in a dry place, away from light and heat sources. Due to radioactivity, it should be stored away from areas of permanent human presence, in a lead container or a dedicated display case with appropriate shielding.