Tungsten

Chemical formula: W

Native tungsten is a naturally occurring, extremely rare form of the element tungsten, found mainly as microscopic inclusions.

## Characteristics Native tungsten is an element and a mineral belonging to the native metals group. It occurs as microscopic, rounded or irregular grains and inclusions within other minerals. Due to its extreme rarity and small crystal size, its visual characteristics are difficult to observe without specialized equipment. Typical specimens have a metallic appearance and a color ranging from silvery-white to steel-gray. ## Physical Properties As a metal, tungsten is characterized by a very high density, theoretically 19.25 g/cm³, making it one of the heaviest minerals. It is opaque and possesses a metallic luster. Its Mohs hardness is rated at 7.5, meaning it is a hard mineral, resistant to scratching. ## Colors and Varieties This mineral does not form colored varieties. Its color is constant, ranging from silvery-white to steel-gray. ## History and Name The name tungsten comes from the German words "wolf" (wolf) and "rahm" (cream, froth), which was an allusion to the difficulties it caused during tin smelting, "devouring" it like a wolf. As an element, it was discovered in 1783, but its occurrence in native form was confirmed much later. The type locality (place of first scientific description) is the Bolshaya Polya River in Russia. ## Uses Native tungsten has no industrial application due to its extreme rarity. It is solely an object of scientific and collecting interest.

Properties

Mohs hardness: 7.5
Luster: Metallic
Streak: Grey
Density: 0
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Isometric

Diagnostic features

## Identification Identifying native tungsten is extremely difficult and practically impossible without advanced analytical methods, such as X-ray microanalysis (EDS/WDS). Preliminary identification relies on finding microscopic, metallic grains with very high density and a steel-gray color in an appropriate geological environment. ## Distinguishing from Similar Minerals It can be confused with other rare native metals, such as platinum, osmium, or iridium, which also form small, dense, metallic grains. Definitive differentiation requires specialized chemical composition analysis. ## Crystal Forms It crystallizes in the isometric system. It is most commonly found as very small, irregular or rounded grains and aggregates. Well-formed crystals are practically unheard of.

Geological environment

## Genesis Native tungsten forms in strongly reducing environments with very low oxygen fugacity. It is found in ultramafic rocks, kimberlites, and also in low-temperature hydrothermal zones associated with serpentinization of rocks. It can also occur in placer deposits as a heavy mineral. ## Mineral Associations It co-occurs with minerals such as chromite, moissanite, graphite, diamond, awaruite, and also with platinum-group minerals. ## Localities The most important confirmed localities worldwide include the Bolshaya Polya River in Siberia (Russia), which is the type locality, as well as some deposits in China and the Urals. However, these occurrences are of purely scientific significance.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its extreme rarity and microscopic nature, the main criterion for a specimen's value is the certainty of its identification. The most valuable samples are those from the type locality or those whose composition has been confirmed by analytical methods. The size of the inclusion, although usually not exceeding fractions of a millimeter, also affects the specimen's attractiveness. ## Popular Localities The only locality of significance for collectors specializing in microscopic minerals is the type locality in Russia. Specimens from other places are practically unavailable on the market.

Care and storage

## Cleaning Specimens of native tungsten are usually microscopic inclusions in other minerals and do not require cleaning. If they are in a host rock, the rock can be mechanically cleaned using a soft brush and distilled water, provided it does not damage co-occurring, more delicate minerals. ## What to Avoid Avoid contact with strong acids and chemicals. Despite its high hardness, specimens should be protected from strong impacts that could damage the host rock. ## Storage Store in stable conditions, away from dust and moisture. Microscopic specimens are best stored in specialized "micromount" boxes, which protect them from loss and mechanical damage.