Oxystibiomicrolite

Chemical formula: (Sb³⁺,Ca)₂Ta⁵⁺₂O₆O

Oxystibiomicrolite is a very rare mineral from the microlite group, an antimony and tantalum oxide, found as small, octahedral crystals.

## Characteristics Oxystibiomicrolite is an extremely rare mineral from the pyrochlore supergroup, belonging to the microlite group. It forms very small, most often isometric crystals with an octahedral habit, less frequently cubo-octahedral, not exceeding 0.3 mm in size. It occurs as single, disseminated crystals or small aggregates. It is brittle. ## Physical Properties Crystals exhibit a hardness of approximately 5 on the Mohs scale. The luster is strong, described as resinous to submetallic. The mineral is opaque. The calculated density is 6.75 g/cm³. ## Colors and Varieties Oxystibiomicrolite has a characteristic, deep red color. No varieties have been distinguished. ## History and Name The mineral was first described in 1978 by P. J. Černý, F. C. Hawthorne, J. J. R. Ladouceur, and T. S. Ercit. Its name refers to its chemical composition – the dominance of oxygen (oxy) and antimony (stibio) – and its relation to the structural microlite group. It was disqualified as a distinct mineral species by the IMA in 2010 as part of the redefinition of the pyrochlore supergroup, and its name now refers to a hypothetical end-member of the series. ## Uses Due to its extreme rarity and microscopic crystal size, oxystibiomicrolite has no practical applications and is solely an object of scientific interest and for specialized collectors of microscopic minerals.

Properties

Mohs hardness: 5.5
Color: Greenish white to white
Luster: Resinous to submetallic
Streak: white
Density: 5.98
Cleavage: Indistinct
Fracture: Irregular/Uneven
Transparency: Translucent
Crystal system: Isometric

Diagnostic features

## Identification Identification of oxystibiomicrolite is based on its characteristic appearance: very small, sharply defined, isometric crystals of intense red color and resinous luster. It occurs in a specific geological environment – in granitic pegmatites. ## Distinguishing from Similar Minerals It can be confused with other red minerals from the pyrochlore group or other small garnets. Certain distinction is almost exclusively possible using advanced analytical methods, such as X-ray microanalysis (EDS/WDS), due to its microscopic size and the need for precise determination of chemical composition. ## Crystal Forms It mainly forms simple, well-developed octahedral crystals {111}, sometimes in combination with cube faces {100}. Crystals are usually single and disseminated in the host rock.

Geological environment

## Genesis Oxystibiomicrolite is a mineral of magmatic origin, crystallizing in the late stages of the evolution of complex granitic pegmatites, especially those rich in lithium, cesium, and tantalum (LCT type), in lithium and cesium mineralized zones. ## Mineral Associations It most commonly co-occurs with quartz, albite, microcline, muscovite, lepidolite, lithiotantite, simpsonite, pollucite, apatite, and beryl. ## Localities The only confirmed and well-described locality for this mineral worldwide is the Tanco pegmatite in Bernic Lake, Manitoba, Canada. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of oxystibiomicrolite micromount specimens is assessed based on the sharpness and size of the crystals, their luster, and the intensity of their red color. The most desirable are sharp, undamaged, single crystals embedded on a contrasting rock matrix, e.g., on white albite or quartz. Due to their size, the photogenicity of the specimen under a microscope is crucial. ## Popular Localities The only source of collector specimens is the Tanco pegmatite in Canada. Material from this locality is extremely rare and sought after by collectors specializing in microscopic minerals (so-called micromounts).

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the microscopic size of the crystals and their brittleness, any mechanical cleaning method (brushes, cotton swabs) is highly risky and can lead to irreversible damage or loss of crystals. ## What to Avoid Avoid contact with all chemicals, including acids and bases. Ultrasonic cleaners should not be used. Protect from shocks and impacts, which can cause delicate crystals to chip off the rock matrix. ## Storage Micromount specimens should be stored in dedicated, sealed boxes that protect against dust and mechanical damage. Store in stable conditions, away from sources of vibration.