Ootannite

Chemical formula: Th⁴⁺₂W⁶⁺₄O₁₆(H₂O)₄·H₂O

Ootannite is an extremely rare, radioactive thorium tungstate mineral, found as microscopic, yellow crystals.

## Characteristics Ootannite is a hydrated thorium tungstate. It occurs as very small, bladed or tabular crystals, rarely exceeding 50 micrometers in length. It forms fan-shaped or radial aggregates. Due to its microscopic size, its visual features are difficult to observe without specialized equipment. ## Physical Properties Ootannite crystals exhibit a vitreous luster. It is a transparent mineral. Its hardness and density have not been precisely measured due to the small size of the samples; however, the density calculated based on the formula and unit cell parameters is 6.45 g/cm³. ## Colors and Varieties This mineral has a characteristic, bright yellow color. No varieties are known. ## History and Name Ootannite was described as a new mineral in 2011 by Peter Elliott. Its name comes from the word "ootann," which means "yellow" in the language of one of the Aboriginal tribes inhabiting northern Queensland, Australia, referring to the mineral's color. It was approved by the International Mineralogical Association (IMA) under number 2010-066. The type locality is the dumps of the Bamford Hill mine in Queensland, Australia. ## Uses Ootannite has no industrial application. Due to its extreme rarity, microscopic size, and status as a type mineral, it is of interest only to specialized collectors and scientific institutions.

Properties

Luster
Vitreous
Streak
Pale yellow
Density
6.45
Cleavage
Good on {100}
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identifying ootannite under amateur conditions is impossible. Identification requires advanced laboratory techniques such as Raman spectroscopy, electron microprobe (EDS/WDS) for chemical composition analysis, and X-ray diffraction (XRD) to confirm the crystal structure. Initial indications may include its bright yellow color, specific form of microscopic crystals, and co-occurrence with other tungsten and thorium minerals in known localities. ## Distinguishing from Similar Minerals It can be confused with other secondary, yellow uranium and thorium minerals. Differentiation from rasite, scheelite, or other rare tungstates is possible only through chemical and structural analysis. ## Crystal Forms It forms very small, bladed crystals, flattened parallel to {100}, which combine into radial or fan-shaped aggregates.

Geological environment

## Genesis Ootannite is a secondary mineral that forms in the oxidation zone of polymetallic deposits containing tungsten and thorium. It originates from the weathering and alteration of primary minerals such as wolframite and thorite, in the presence of water. ## Mineral Associations At the type locality in Australia, it co-occurs with quartz, fluorite, wolframite, native bismuth, bismuthinite, scheelite, rasite, and thorite. ## Localities The only confirmed occurrence of ootannite in the world is its type locality – the mine dumps of Bamford Hill Mines, near Bamford, Mareeba Shire, Queensland, Australia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of an ootannite specimen is determined by the abundance and development of microscopic crystals on the rock matrix. The most desirable samples are those with clearly visible, well-formed, radial aggregates of intense yellow color. Due to the microscopic nature of the mineral, the aesthetics of the entire "micromount" specimen and the quality of the microphotography are crucial. ## Popular Localities The only source of specimens, including those of collector's value, is the type locality in Bamford, Australia. Specimens from this locality are extremely difficult to acquire and represent a rarity in specialized collections of rare minerals and "micromount" type.

Care and storage

## Cleaning Ootannite specimens, due to their microscopic size and fragility, should generally not be mechanically cleaned. Any attempts at cleaning may destroy the delicate crystals. If absolutely necessary, compressed air can be carefully used from a safe distance. ## What to Avoid Avoid contact with any chemicals, ultrasonics, and all forms of mechanical cleaning. As a thorium-bearing mineral, it is radioactive, so direct exposure should be limited, and inhalation of dust that might arise from sample damage should be avoided. ## Storage Specimens should be stored under stable conditions, away from vibrations and dust, preferably in a closed, padded "micromount" box. Due to its radioactivity, it is recommended to store it away from other minerals that could be damaged by radiation, and away from areas of permanent human presence.

External references

Sources

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