Athabascaite

Chemical formula: Cu<sub>5</sub>Se<sub>4</sub>

Athabascaite is a very rare copper selenide, occurring as fine, metallic aggregates in uranium deposits.

## Characteristics Athabascaite is a rare mineral from the sulfide group, specifically a copper selenide. It most often forms massive, granular, or fibrous aggregates, as well as fine veinlets in the host rock. It is rarely observed in the form of primitive, platy crystals, usually submillimeter in size. It has a metallic luster and is opaque. Its color is gray to grayish-white, often with a blackish tint. In air, it tarnishes over time and develops a bluish-black coating. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of about 2.5. It is characterized by a high density of 6.58 g/cm³. It is brittle, and its fracture is uneven to subconchoidal. It does not exhibit cleavage. It is a good electrical conductor. ## Colors and Varieties Athabascaite occurs in shades of gray – from light gray to almost black. Its tarnishing to a bluish-black color is characteristic. No color or commercial varieties are distinguished. ## History and Name The mineral was first described in 1970 by D.C. Harris, L.J. Cabri, and S. Kaiman. Its name comes from the discovery locality – the Athabasca Lake region in Saskatchewan, Canada. Type specimens come from the Martin Lake mine. ## Uses Due to its extreme rarity, athabascaite has no industrial application. It is solely an object of scientific interest and a prized acquisition for advanced collections of rare and systematic minerals.

Properties

Mohs hardness
2.5
Luster
Metallic
Streak
Black
Density
6.58
Cleavage
None
Fracture
Uneven
Transparency
Opaque
Crystal system
Orthorhombic

Diagnostic features

## Identification Athabascaite is identified by its metallic luster, gray color, black streak, and high density. A key diagnostic clue is its occurrence in paragenesis with other, often rare selenides within low-temperature hydrothermal formations, especially in uranium deposits. ## Distinguishing from Similar Minerals It can be confused with other gray, metallic selenides, such as umangite, berzelianite, eucairite, or clausthalite. Umangite often exhibits a purplish tint, which can be a distinguishing feature. However, certain identification is almost exclusively possible using advanced laboratory methods, such as chemical composition analysis (EDS) or X-ray diffraction (XRD). ## Crystal Forms Athabascaite crystallizes in the orthorhombic system. It most often forms massive, compact, or granular aggregates. Small, platy or acicular crystals are rarely found, usually as intergrowths with other minerals.

Geological environment

## Genesis It is a hydrothermal mineral, forming under low-temperature conditions. It occurs in ore veins, most often associated with uranium mineralization. It is found in carbonate-quartz veinlets cutting altered sandstones or basalts. ## Mineral Associations Athabascaite often co-occurs with other selenides, such as umangite, berzelianite, eucairite, clausthalite, klockmannite, eskebornite, and tyrrellite. It is also accompanied by native selenium, uranium oxides (uraninite), native gold, chalcopyrite, and pyrite. ## Localities The most important localities worldwide are the Athabasca Lake region (Martin Lake and Eagle-Ace mines) in Saskatchewan, Canada. This mineral has also been found in the Czech Republic (Třebsko near Příbram), Germany (Eskaborner Stollen in the Harz Mountains), and Argentina (Sierra de Cacho).

Rarity

Very rare

For collectors

## Quality Criteria The quality of athabascaite specimens is primarily assessed based on the richness of aggregates and the confirmed presence of rare associated minerals. Since it is mainly a micromineral, the size of the aggregate is crucial. Specimens with well-defined veinlets or rich impregnations in the host rock are most desirable. Samples from the type locality (Athabasca Lake) are highly valued. ## Popular Localities The most prized specimens by collectors come from historical localities in Canada (Athabasca Lake region) and from Příbram, Czech Republic. These are classic localities for this mineral, and material from them serves as a reference for the species.

Care and storage

## Cleaning Athabascaite specimens should only be dry-cleaned using a soft brush to remove dust. All contact with water and chemical agents, which can lead to oxidation and permanent damage to the mineral, should be avoided. ## What to Avoid The mineral is sensitive to moisture and acidic environments. Prolonged exposure to air can cause it to tarnish and change color. It should be protected from chemicals, especially acids and cleaning agents. ## Storage It is recommended to store specimens in a dry, stable environment, preferably in tightly sealed collector boxes (so-called "membrane boxes" or in a box with a moisture absorber) to limit air access and prevent oxidation processes.

External references

Sources

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