Hydroxykenoelsmoreite

Chemical formula: (&#9744;,Pb<sup>2+</sup>)<sub>2</sub>(W<sup>6+</sup>,Fe<sup>3+</sup>,Al)<sub>2</sub>(O,OH)<sub>6</sub>(OH)

Hydroxykenoelsmoreite is a rare mineral from the elsmoreite group, an oxide of tungsten, lead, and iron, forming microscopic, octahedral crystals.

## Characteristics Hydroxykenoelsmoreite is a very rare oxide mineral from the elsmoreite group, belonging to the pyrochlore supergroup. It occurs as very small, usually microscopic, octahedral crystals, rarely exceeding 0.2 mm in size. These crystals often form aggregates or coatings. Due to their size, visual features are difficult to observe without specialized equipment, such as a scanning electron microscope (SEM). ## Physical Properties Hydroxykenoelsmoreite crystals exhibit a luster ranging from resinous to adamantine. Hardness and density have not been precisely measured due to the small size of samples, but the calculated density is approximately 6.75 g/cm³. The mineral is brittle. ## Colors and Varieties Observed colors of hydroxykenoelsmoreite range from light yellow, through yellowish-orange, to brownish. No named varieties of this mineral have been distinguished. ## History and Name The mineral was first described by D.E. Hibbs and co-workers in 2003 based on material from the Elsmore mine in New South Wales, Australia. Its name refers to its chemical composition – the dominance of the hydroxyl (OH) group – and its relationship to other minerals of the elsmoreite group, particularly kenoelsmoreite. It was approved by the International Mineralogical Association (IMA) under number 2002-040. ## Uses Hydroxykenoelsmoreite has no industrial application. Its significance is purely scientific and as a collector's item, being a very rare and specific member of the pyrochlore supergroup.

Properties

Luster
Resinous to adamantine
Streak
Light yellow
Density
6.75
Cleavage
None
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Isometric

Diagnostic features

## Identification Identification of hydroxykenoelsmoreite is impossible without advanced analytical techniques. Characteristic, microscopic, octahedral crystals with a yellow color are the first clue, but definitive identification requires chemical analysis (e.g., using an electron microprobe - EDS/WDS) to confirm the presence of tungsten, lead, and iron and the absence of other key elements. X-ray diffraction (XRD) is necessary to confirm the crystal structure. ## Distinguishing from Similar Minerals Hydroxykenoelsmoreite can be confused with other minerals from the elsmoreite group (kenoelsmoreite, hydrokenoelsmoreite) and other secondary tungsten and lead minerals of yellow color, such as raspite, stolzite, or mimetite. Differentiation from kenoelsmoreite and hydrokenoelsmoreite is possible only based on precise chemical composition and structural analysis. It differs from other minerals by its crystal habit (octahedra) and specific composition. ## Crystal Forms This mineral forms only small, well-formed, equant crystals with an octahedral habit {111}. The crystal size usually does not exceed 0.2 mm. They occur as single crystals grown on the host rock or in the form of aggregates and coatings.

Geological environment

## Genesis Hydroxykenoelsmoreite is a secondary mineral, forming in the oxidation (weathering) zones of ore deposits rich in tungsten (usually from wolframite) and lead (from galena). It forms under low-temperature conditions as a result of surface water interaction with primary ore minerals. ## Mineral Associations This mineral co-occurs with other secondary minerals of the oxidation zone. In the type locality (Elsmore, Australia), it was found in association with quartz, kenoelsmoreite, ferberite, arsenopyrite, galena, pyromorphite, and raspite. ## Localities Confirmed occurrences of hydroxykenoelsmoreite are extremely rare. Besides the type locality in the Elsmore mine in Gough County, New South Wales (Australia), it has been identified in the Clara mine in the Black Forest (Germany) and the Carrock Fell mine in Cumbria (England).

Rarity

Very rare

For collectors

## Quality Criteria The quality of a hydroxykenoelsmoreite specimen primarily depends on the presence of well-formed, sharp, and clearly visible crystals under magnification. Specimens where microcrystals are abundant, form rich aggregates, and contrast colorfully with the rock matrix are most valued. The intensity and purity of the yellow or orange color also enhance aesthetic value. Due to the microscopic nature of the mineral, the quality of the accompanying photomicrograph is crucial. ## Popular Localities The most known and classic locality, from which the best specimens originate, is the type locality – the Elsmore mine in Australia. Specimens from the Clara mine in Germany are also known among collectors specializing in microscopic minerals ("micromounts").

Care and storage

## Cleaning Due to the extreme rarity and microscopic size of the crystals, hydroxykenoelsmoreite specimens are practically not subject to cleaning. Any attempts at mechanical or chemical cleaning can irreversibly damage the delicate crystals. If cleaning is absolutely necessary, compressed air (from a safe distance) can be carefully used to remove loose dust particles. ## What to Avoid Avoid contact with any chemicals, including acids and bases. Do not use ultrasonic cleaners. Protect the specimen from shocks, impacts, and abrasion, which could detach microcrystals from the matrix. ## Storage Specimens should be stored in stable conditions, away from dust and vibrations. The best solution is a sealed "micromount" box, which protects the sample from mechanical damage and contamination. Exposure to strong light is not recommended, although there is no specific data on its effect on this mineral.

Sources

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