Calcurmolite
Chemical formula: (Ca₁-xNax)₂(U⁶⁺O₂)₃(Mo⁶⁺O₄)₂(OH)₆-x·nH₂O
Calcurmolite is a rare secondary uranium and molybdenum mineral, forming bright yellow, radial aggregates and coatings in the oxidation zones of uranium deposits.
Properties
- Mohs hardness
- 2-3
- Density
- 0
- Transparency
- Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Calcurmolite can be identified by its characteristic bright yellow color, radial or fibrous aggregates, and occurrence in the oxidation zones of uranium deposits. It is very soft and delicate. The reaction to UV radiation (weak, greenish-yellow fluorescence) can be helpful but is not always observable. A key indicator is its radioactivity. ## Distinguishing from similar minerals It can be confused with other yellow secondary uranium minerals such as uranophane, carnotite, or tyuyamunite. Uranophane often forms similar radial aggregates but crystallizes in the monoclinic system and has a slightly different hardness. Carnotite and tyuyamunite are usually brighter yellow and often occur in sedimentary rocks (sandstones). Accurate differentiation requires advanced chemical (EDS) or X-ray (XRD) analyses. ## Crystal forms It forms very fine, acicular or hair-like crystals that combine into radial, stellate, or spherulitic aggregates. It also occurs as fibrous, reniform aggregates, as well as coatings and earthy encrustations on other minerals.
Geological environment
## Genesis Calcurmolite is a secondary mineral, forming in the oxidation (weathering) zones of hydrothermal uranium-molybdenum deposits. It forms as a result of oxygen-rich waters acting on primary uranium minerals (e.g., uraninite) and molybdenum minerals (e.g., molybdenite). ## Mineral associations It most often co-occurs with other minerals from the oxidation zone. Its typical associated minerals include uranophane, iriginite, calcite, gypsum, as well as relics of primary ore minerals such as uraninite and molybdenite. ## Localities The most important and classic locality (type locality) of this mineral is in Armenia, in the Sokh-Karasu region of Syunik Province. It is also known from other uranium-molybdenum deposits, including those in the Czech Republic and Germany.
Rarity
Very rare
For collectors
## Quality criteria Specimens with well-formed, distinct radial aggregates of intense, bright yellow color are most valued by collectors. Contrast with the dark host rock is important, as it highlights the mineral's form and color. Large, undamaged aggregates are much rarer and more desirable. Specimens with a well-defined locality, especially from the type locality in Armenia, have higher value. ## Popular localities The most known and valued specimens come from the type locality in Armenia. Other localities from which collectible specimens may originate include some uranium deposits in the Czech Republic and Germany, however, material from these places is much rarer on the market.
Care and storage
## Cleaning Calcurmolite specimens are extremely delicate and fragile. Cleaning should be kept to an absolute minimum. If necessary, a soft brush can be used to remove dust or compressed air from a safe distance. Avoid contact with water, which can damage or dissolve the mineral. ## What to avoid Absolutely avoid contact with water and all chemicals. The mineral is sensitive to changes in temperature and humidity. As a uranium mineral, it is radioactive – avoid inhaling dust and wash hands after any contact with the specimen. ## Storage Specimens should be stored in closed, airtight containers (e.g., "perky box" type) to protect them from mechanical damage, dust, and moisture. Due to its radioactivity, it should be kept away from areas of constant human presence, in a well-ventilated room. It should be appropriately labeled as radioactive material.