Ansermetite

Chemical formula: Mn<sup>2+</sup>V<sup>5+</sup><sub>2</sub>O<sub>6</sub>·4H<sub>2</sub>O

Ansermetite is a very rare hydrated manganese vanadate, forming microscopic, acicular crystals of an orange color.

## Characteristics Ansermetite is a hydrated manganese vanadate, occurring as extremely small, acicular or bladed crystals, rarely exceeding 0.2 mm in length. These crystals form rosette-like or radial aggregates, as well as thin coatings and crusts on rock surfaces. Due to the microscopic size of the crystals, its visual features are difficult to observe without specialized equipment. ## Physical Properties Ansermetite crystals exhibit an orange color and vitreous luster. They are transparent to translucent. Hardness and density have not been precisely measured due to the small size and rarity of the material, but the hardness is estimated to be around 2 on the Mohs scale. It is a very brittle mineral. ## Colors and Varieties This mineral occurs in a uniform, characteristic orange color. No varieties have been distinguished. ## History and Name Ansermetite was discovered in the dumps of the former Mounana uranium mine in Gabon. It was described and approved as a new mineral by the International Mineralogical Association (IMA) in 1998. Its name honors the Swiss mineral collector, Francis Ansermet (born 1952), who found the first samples of this mineral and submitted them for scientific research. ## Uses Ansermetite has no industrial application. Its significance is purely scientific and collectible, as a very rare and unique representative of the vanadate group.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Light orange
Density
2.54
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identifying ansermetite under amateur conditions is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical spectroscopy (EDS/WDS). Preliminary identification in a collection is based on the characteristic orange color, acicular crystal habit forming radial aggregates, and knowledge of the locality (Mounana mine). ## Differentiation from Similar Minerals Ansermetite can be confused with other secondary vanadium minerals of similar color and form, such as pascoite or hewettite. However, pascoite is water-soluble, yielding a yellow solution. Hewettite has a darker, reddish-brown color. Final differentiation requires specialized laboratory tests. ## Crystal Forms Ansermetite forms very fine, acicular or bladed crystals, elongated along the [001] axis. These crystals combine into characteristic, radial or rosette-like aggregates, and also form thin coatings on the host rock.

Geological environment

## Genesis Ansermetite is a secondary mineral, formed in the oxidation zone of uranium-vanadium deposits hosted in sedimentary rocks (sandstones). It forms as a result of weathering and alteration of primary vanadium minerals under conditions of low temperatures and pressures, in the presence of manganese. ## Mineral Associations This mineral occurs in association with other secondary vanadium and uranium minerals. It most commonly co-occurs with francevillite, chervetite, curienite, duttonite, as well as with gypsum, barite, and manganese oxides (such as cryptomelane). ## Localities The only confirmed locality for ansermetite in the world is its type locality – the former Mounana uranium mine, located in the Haut-Ogooué Province in Gabon.

Rarity

Very rare

For collectors

## Quality Criteria The quality of ansermetite specimens is primarily assessed based on the richness and aesthetics of the crystal aggregates. Most prized are samples with well-formed, radial rosettes of intense orange color, clearly contrasting with the dark host rock. Due to the microscopic nature of the mineral, specimens are evaluated under magnification. The presence of rare associated minerals is also important. ## Popular Localities The only source of collectible specimens is the Mounana mine in Gabon. Material from this locality is extremely rare and sought after by specialized collectors of systematic minerals and those focusing on rare species.

Care and storage

## Cleaning Ansermetite specimens are extremely delicate and susceptible to mechanical damage. Cleaning should be limited to an absolute minimum. If necessary, compressed air (from a safe distance) can be used to remove loose dust particles. Any contact with water, brushes, or other tools should be avoided. ## What to Avoid Contact with water and chemicals, which can dissolve or damage the microscopic crystals, must be strictly avoided. The mineral is sensitive to changes in temperature and humidity. It should not be heated or exposed to direct sunlight, which can cause dehydration and destruction. ## Storage Specimens should be stored under stable conditions, preferably in closed, airtight "micromount" containers, which protect against dust, moisture, and physical damage. Display should be away from sources of vibration, heat, and light.

Sources

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