Calciotantite
Chemical formula: CaTa⁵⁺₄O₁₁
Calciotantite is a very rare, colorless tantalum and calcium oxide mineral, found as small, hexagonal crystals.
Properties
- Mohs hardness
- 6.5
- Luster
- Adamantine
- Streak
- White
- Density
- 7.46
- Transparency
- Transparent
- Crystal system
- Hexagonal
Diagnostic features
## Identification Amateur identification of calciotantite is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) or X-ray microanalysis (EDS/WDS), due to its microscopic size and similarity to other colorless minerals. ## Distinguishing from Similar Minerals It can be confused with other colorless minerals found in pegmatites, such as quartz, phenakite, or herderite. Differentiation is based on chemical and crystallographic analysis. Its very high density is a distinguishing feature, but impossible to measure for microcrystals. ## Crystal Forms It forms small, hexagonal crystals with tabular or short-prismatic habit. They usually occur as single, well-formed crystals embedded in the host rock.
Geological environment
## Genesis Calciotantite is a magmatic mineral, crystallizing in the late stages of the evolution of granitic pegmatites, especially those with an extremely differentiated composition, rich in rare earth elements and tantalum. ## Mineral Associations It co-occurs with other minerals typical of pegmatites, such as microcline, quartz, albite, as well as rarer tantalum minerals, e.g., microlite, wodginite, and yttrotantalite-(Y) (formerly yttrotantalite). ## Localities The most important and also the type locality of calciotantite is the Vasin-Mylk massif in the Voroniy Tundry region on the Kola Peninsula in Russia. This is the only confirmed and well-documented locality of this mineral in the world.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a calciotantite specimen is primarily judged by the size and development of its crystals, which is a rarity. Specimens with distinct, sharp crystals, even if microscopic in size, are most valued. Contrast with the surrounding host rock, which facilitates observation, is also important. ## Popular Localities The only source of collector specimens is the type locality on the Kola Peninsula in Russia. Specimens from this location are extremely difficult to obtain and appear on the market very sporadically.
Care and storage
## Cleaning Calciotantite specimens are usually microscopic and embedded in the host rock. Cleaning is not recommended to avoid damaging or losing the fragile crystals. If absolutely necessary, compressed air can be used to remove dust. ## What to Avoid Avoid contact with chemicals, ultrasonics, and any mechanical cleaning methods, such as brushing. The mineral is hard, but its small crystals are susceptible to mechanical damage. ## Storage Specimens should be stored in stable conditions, in sealed "micromount" boxes, to protect them from dust and damage. Shocks and vibrations should be avoided.