Oxystannomicrolite
Chemical formula: Sn<sup>2+</sup><sub>2</sub>Ta<sup>5+</sup><sub>2</sub>O<sub>6</sub>O
Oxystannomicrolite is a very rare oxide from the microlite group, distinguished by the presence of tin and tantalum and high density.
Properties
- Mohs hardness
- 5-5.5
- Luster
- Adamantine
- Streak
- Reddish-brown
- Density
- 6.96
- Cleavage
- Indistinct on {111}
- Fracture
- Conchoidal
- Transparency
- Translucent to opaque
- Crystal system
- Cubic
Diagnostic features
## Identification Identifying oxystannomicrolite in practice is impossible without advanced analytical methods, such as X-ray microanalysis (EDS/WDS). Preliminary suspicion can be raised based on the characteristic octahedral crystal form, dark red color, adamantine luster, and co-occurrence with other pegmatite minerals in known localities. ## Distinguishing from Similar Minerals It can be confused with other minerals from the pyrochlore group, such as microlite, pyrochlore, or uranmicrolite, as well as with garnets (e.g., spessartine) or spinel. Distinguishing it from these minerals requires specialized chemical analysis, as all can form similar octahedral crystals. ## Crystal Forms It forms very small, sharp, well-formed crystals with an octahedral {111} habit. Crystals usually occur as single individuals grown on the surface of other minerals, less frequently in small aggregates.
Geological environment
## Genesis Oxystannomicrolite is a mineral of magmatic origin. It forms in the late stage of crystallization in highly differentiated, rare-element-rich LCT (lithium-cesium-tantalum) type granitic pegmatites. ## Mineral Associations This mineral co-occurs with other rare pegmatite minerals. In the type locality (Tanco Mine), it was found in association with cassiterite, tantalite-(Mn), wodginite, titanowodginite, simpsonite, apatite, and quartz. ## Localities It is an extremely rare mineral, known from only a few locations worldwide. The most important ones are: - Tanco Mine, Bernic Lake, Manitoba, Canada - type locality. - Alto Ligonha Mine, Zambezia Province, Mozambique.
Rarity
Extremely rare
For collectors
## Quality Criteria The most important criterion for specimen value is the quality and size of the crystals. Sharp, undamaged, well-formed octahedra, preferably with an intense red color, are sought after. Due to the microscopic size of the crystals, the aesthetics of the rock matrix on which they are embedded is also crucial. The color contrast between oxystannomicrolite and the substrate (e.g., white quartz) significantly enhances the specimen's attractiveness. ## Popular Localities The most known and valued specimens, though still microscopic, come from the type locality at the Tanco Mine in Canada. Material from Mozambique is also known but less commonly found on the collector's market.
Care and storage
## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the extreme rarity and small size of the crystals, any mechanical contact, including cleaning with brushes or water, which could damage or dislodge tiny crystals from the matrix, should be avoided. ## What to Avoid Avoid contact with chemicals, acids, and ultrasonics. The mineral is brittle, so it must be protected from impacts and vibrations. It should not be heated or exposed to sudden temperature changes. ## Storage Specimens should be stored under stable conditions, in a sealed "micromount" box, to protect them from dust, mechanical damage, and loss. Avoid exposure to direct sunlight, although its light sensitivity is not known.