Chaméanite

Chemical formula: (Cu,Fe)<sub>4</sub>As(Se,S)<sub>4</sub>

Chaméanite is an extremely rare copper iron arsenoselenide, occurring as microscopic, metallic-gray grains.

## Characteristics Chaméanite is a member of the tetrahedrite group, classified as a copper iron arsenoselenide. It occurs as very small, anhedral grains, rarely exceeding 0.1 mm in diameter. Its appearance is inconspicuous – it has a metallic luster and is steel-gray to gray in color. It typically forms inclusions in other minerals or occurs as thin rims around hakite crystals. ## Physical Properties The Mohs hardness of chaméanite is approximately 4.5. It is a brittle and opaque mineral, with a measured density of 5.15 g/cm³. It has a metallic luster and a black streak. ## Colors and Varieties This mineral is uniform in color, always appearing in shades from steel-gray to gray. No colored varieties or commercial forms are known. ## History and Name Chaméanite was first described in 1981 by Z. Johan, P. Picot, and F. Ruhlmann. Its name comes from its discovery locality – the mineralization at Chaméane, in the Puy-de-Dôme department in France. ## Uses Due to its extreme rarity and occurrence as microscopic grains, chaméanite has no commercial or industrial applications. It is solely an object of scientific and collecting interest for specialists in rare minerals.

Properties

Mohs hardness
4.5
Luster
Metallic
Streak
Black
Density
5.15
Cleavage
None
Fracture
Uneven
Transparency
Opaque
Crystal system
Cubic

Diagnostic features

## Identification Identification of chaméanite is impossible without advanced analytical techniques. Its microscopic size, gray color, and metallic luster make it visually indistinguishable from many other sulfides, selenides, and arsenides. Definitive identification requires chemical composition analysis using an electron microprobe (EDS/WDS). ## Distinguishing from Similar Minerals Chaméanite can be easily confused with co-occurring minerals such as hakite, krutaite, tetrahedrite, or eskebornite. All these minerals form similar, gray, metallic grains. Distinguishing them from each other relies solely on chemical analysis. ## Crystal Forms This mineral forms exclusively anhedral (irregular) grains. No well-formed crystals have been observed. It sometimes occurs as thin rims (coatings) growing on hakite crystals.

Geological environment

## Genesis Chaméanite forms under low-temperature hydrothermal conditions. In its type locality (Chaméane, France), it occurs in quartz-barite veins cutting gneisses. It is a product of crystallization from solutions rich in selenium and arsenic. ## Mineral Associations This mineral occurs in association with other rare selenides and sulfosalts. The most common associated minerals include: hakite, berzelianite, umangite, bukovite, krutaite, eskebornite, tetrahedrite, as well as chalcopyrite, pyrite, native arsenic, native selenium, uraninite, and quartz. ## Localities Chaméanite is an extremely rare mineral, confirmed in only a few localities worldwide. The most important of these are the type locality in Chaméane (Auvergne-Rhône-Alpes region, France) and the Předbořice deposit in the Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare micromineral, the main criterion of value is its confirmed presence on the specimen, especially from the type locality. The size of the grains (though always microscopic) and the richness of associated minerals can increase the attractiveness of the specimen for a specialized collector. Purity or form are not applicable. ## Market Prices There is no established market for this mineral. Specimens appear sporadically in circulation between specialized collectors and scientific institutions, and their price is the result of individual negotiations. ## Popular Localities The most prized specimens come from two main localities: Chaméane in France and Předbořice in the Czech Republic. Specimens from these locations serve as a reference point for this mineral.

Care and storage

## Cleaning Chaméanite specimens are typically microscopic grains on a rock matrix that do not require cleaning. Any attempt at mechanical or chemical cleaning risks irreversible damage or loss of the mineral. If necessary, a dusty specimen can be gently blown with compressed air from a safe distance. ## What to Avoid Avoid contact with moisture, water, and all chemicals, especially acids, which can quickly destroy the mineral. As a selenide and arsenide, it is susceptible to oxidation in a humid environment. Protect it from temperature changes and direct sunlight. ## Storage The best way to store it is in a sealed, closed "micromount" box, which protects against dust, moisture, and mechanical damage. Store in stable room conditions.

Sources

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