Tarkianite

Chemical formula: (Cu,Fe)(Re,Mo)<sub>4</sub>S<sub>8</sub>

Tarkianite is a rare copper, iron, rhenium, and molybdenum sulfide, forming tiny, metallic inclusions in other minerals.

## Characteristics Tarkianite is a very rare mineral from the sulfide group. It occurs as microscopic, rounded or irregular grains and inclusions within other sulfides, mainly molybdenite. Its grains rarely exceed 100 micrometers in size. It is usually opaque and has a metallic luster, and its color in reflected light is creamy white with a pinkish tint. ## Physical Properties Due to the microscopic size of the grains, most physical properties, such as hardness, density, cleavage, or fracture, have not been precisely determined. It is an opaque mineral with a metallic luster. ## Colors and Varieties This mineral does not form varieties. Its color observed under a microscope in reflected light is characteristic – creamy white with a distinct pinkish or pinkish-brown tint. ## History and Name The name tarkianite comes from the name of Professor Mehmet Tarkian (1942-2004), a mineralogist from the University of Hamburg in Germany, in recognition of his contribution to ore mineralogy. The mineral was discovered and described in 2005 based on material from the Aitik copper and molybdenum deposit in Gällivare, Lapland (Sweden). ## Uses Tarkianite has no industrial application. It is solely an object of scientific and collecting interest due to its extreme rarity and rhenium-rich chemical composition.

Properties

Luster
Metallic
Cleavage
None
Transparency
Opaque
Crystal system
Cubic

Diagnostic features

## Identification Identification of tarkianite is only possible using advanced laboratory techniques, such as reflected light ore microscopy and chemical analysis using an electron microprobe (EDS/WDS). Its characteristic creamy white color with a pinkish tint in reflected light and high rhenium content are diagnostic. ## Distinguishing from Similar Minerals Under the microscope, it can be confused with other rare rhenium or molybdenum sulfides. Definitive differentiation requires chemical composition analysis. It differs from the usually surrounding molybdenite by its color and significantly higher reflectivity. ## Crystal Forms Tarkianite does not form well-developed crystals. It occurs as anhedral (irregular), rounded grains and inclusions in other minerals.

Geological environment

## Genesis Tarkianite forms under hydrothermal conditions. In its type locality (Aitik deposit), it is associated with quartz-molybdenite veins cutting copper deposits. Its formation is linked to crystallization from solutions rich in copper, iron, rhenium, and molybdenum. ## Mineral Associations This mineral most commonly co-occurs with molybdenite (often as inclusions within it), chalcopyrite, bornite, tennantite, pyrite, and quartz. ## Localities Confirmed occurrences of tarkianite are extremely rare. Besides the type locality in the Aitik deposit in Sweden, it has been identified in the Aksug porphyry copper-molybdenum deposit in Russia (Siberia) and the Sar Cheshmeh mine in Iran.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to the microscopic nature of tarkianite, the collector's value of a specimen is inextricably linked to the quality of the entire rock fragment or polished section. The most valuable specimens are those with analytically confirmed presence of tarkianite, originating from the type locality (Aitik, Sweden). The size and richness of tarkianite grain aggregates, visible under a microscope, increase their scientific and collector's value. ## Popular Localities The only source of specimens of collector's significance is the type locality – the Aitik deposit in Gällivare, Sweden.

Care and storage

## Cleaning Specimens containing tarkianite, which are usually polished sections or rock fragments, should only be cleaned with compressed air to remove dust. Any wet cleaning is discouraged due to the microscopic nature of the mineral and the risk of damaging the surrounding matrix. ## What to Avoid Avoid contact with chemicals, acids, and ultrasonic cleaners. Tarkianite, as a sulfide, may be susceptible to oxidation and chemical reactions. It should be protected from moisture and sudden temperature changes. ## Storage Specimens containing tarkianite are best stored in stable conditions, in a dry place, in a closed display box, to protect them from dust and contaminants. Due to their microscopic nature, these specimens are usually already appropriately secured in the form of microscopic preparations or embedded in resin.

External references

Sources

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