Joliotite
Chemical formula: (U⁶⁺O₂)(CO₃)·2H₂O
Joliotite is a very rare, secondary uranyl mineral, forming microscopic, yellow crystals and coatings in the oxidation zones of uranium deposits.
Properties
- Mohs hardness
- 1-2
- Color
- Citron-yellow
- Luster
- Vitreous to pearly
- Streak
- Yellow
- Density
- 4.04
- Cleavage
- {100}, probable.
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Joliotite is identified by its canary yellow color, mode of occurrence (fine coatings and microscopic crystals), strong radioactivity, and characteristic bright yellow fluorescence under UV light. Identification usually requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other yellow secondary uranium minerals, such as studtite, rutherfordine, or schoepite. Studtite forms acicular crystals; rutherfordine has a similar composition but a different crystal structure and often forms larger, earthy aggregates. Final distinction is almost exclusively possible through laboratory analysis. ## Crystal Forms It forms microscopic, tabular or bladed crystals, often flattened. These crystals group into rosette-like or radial aggregates, and also form thin crusts and coatings.
Geological environment
## Genesis Joliotite is a secondary mineral, formed in the oxidation zones of uraninite (pitchblende) deposits. It forms as a result of the weathering of primary uranium ores in the presence of carbonate-rich waters. It is one of the alteration products of uraninite under near-surface conditions. ## Mineral Associations It most commonly co-occurs with uraninite (as the primary mineral) and other secondary uranium minerals, such as studtite, rutherfordine, schoepite, as well as with quartz and hematite. ## Localities The type locality, from which it was first described, is the Krunkelbach uranium mine in Menzenschwand in the Black Forest (Baden-Württemberg, Germany). It is also known from several other locations worldwide, including Jáchymov in the Czech Republic and the Lake Athabasca region in Saskatchewan, Canada.
Rarity
Very rare
For collectors
## Quality Criteria The collector's appeal of a joliotite specimen depends on the richness of the coating and the visibility of individual crystal aggregates under a microscope. The most valued samples are those where the mineral forms distinct, rosette-like clusters of intense yellow color, contrasting well with the host rock. Due to its microscopic nature, the quality of the specimen as seen under magnification is crucial. ## Popular Localities The most classic and sought-after specimens by collectors come from the type locality – the Krunkelbach mine in Germany.
Care and storage
## Cleaning Joliotite specimens are generally not cleaned. Any attempts at mechanical or chemical cleaning will almost certainly destroy the microscopic crystals. If absolutely necessary, compressed air (from a safe distance) can be used to remove loose dust. ## What to Avoid Avoid contact with water, chemicals, acids, and all cleaning agents. The crystals are extremely brittle and sensitive to shock and abrasion. As a secondary mineral, it is unstable under varying humidity and temperature conditions. ## Storage Due to strong radioactivity, specimens should be stored in specialized, lead-lined containers, away from other radiation-sensitive minerals. Store in a dry place, in tightly sealed "micromount" boxes, to protect delicate crystals from mechanical damage and dust.