Moluranite
Chemical formula: H₄U⁴⁺(U⁶⁺O₂)₃(Mo⁶⁺O₄)₇·18H₂O
Moluranite is a rare, amorphous uranium and molybdenum mineral, forming black, resinous masses and coatings.
Properties
- Mohs hardness
- 3-4
- Luster
- Resinous
- Density
- 4.
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Amorphous
Diagnostic features
## Identification Moluranite is identified by its black color, resinous luster, and massive, amorphous form. A key diagnostic feature is its very strong radioactivity, easily detectable with a Geiger-Müller counter. It occurs in paragenesis with other uranium and molybdenum minerals. ## Distinguishing from Similar Minerals It can be confused with other black uranium oxides, such as uraninite (pitchblende). However, uraninite is usually harder (5-6 on the Mohs scale) and crystallizes in the isometric system, often forming regular crystals or aggregates with a characteristic tar-like luster and conchoidal fracture. Definitive differentiation requires specialized tests, e.g., X-ray diffraction (XRD). ## Crystal Forms Moluranite is amorphous, meaning it does not form crystals. It occurs as compact, earthy, reniform aggregates or as thin crusts and veinlets in the host rock.
Geological environment
## Genesis Moluranite is a secondary mineral, formed in the oxidation (weathering) zones of uranium-molybdenum deposits. It forms as a result of the alteration of primary uranium minerals, such as uraninite, in the presence of molybdenum-rich solutions. ## Mineral Associations It most commonly co-occurs with other minerals from the oxidation zone. Typical associated minerals include uraninite, wulfenite, molybdenite, umohoite, as well as various secondary copper and iron minerals. ## Localities The most important and type locality is the Alexandrovskii Golets deposit on the Aldan Shield in Russia. It is a very rare mineral, and its confirmed occurrences worldwide are few and limited to specific weathering zones of U-Mo deposits.
Rarity
Very rare
For collectors
## Quality Criteria The collector's appeal of moluranite does not depend on its aesthetics, which are minimal, but on its rarity and scientific significance. The most valued specimens are rich, with a clearly visible mass of the mineral, well-seated on a small rock matrix. Well-documented locality and paragenesis with other rare secondary minerals are also important. ## Popular Localities The only source of collector-grade specimens is its type locality in Russia (Alexandrovskii Golets). Specimens from this location are extremely difficult to acquire on the market.
Care and storage
## Cleaning Moluranite specimens should not be cleaned wet. Any contaminants, such as dust, should be removed only with a soft brush or compressed air. Contact with water can lead to the slow decomposition of the mineral. ## What to Avoid Contact with water, acids, and other chemicals must be strictly avoided. As a strongly radioactive mineral, it requires special precautions. Direct skin contact, inhalation of dust, and storage in areas of permanent human presence should be avoided. ## Storage Moluranite specimens must be stored in specialized, lead-lined containers that isolate radiation. These containers should be airtight, protect against moisture, and be clearly marked with the international radioactivity symbol. They should be kept in a well-ventilated room, away from bedrooms and living areas.