Tellurohauchecornite

Chemical formula: Ni₉BiTeS₈

Tellurohauchecornite is a very rare, metallic nickel, bismuth, tellurium, and sulfur mineral, forming small grains embedded in rock.

## Characteristics Tellurohauchecornite is an extremely rare mineral from the sulfide group, specifically a nickel and bismuth sulfotelluride. It occurs as very small, anhedral (lacking crystal faces) grains, which are embedded in other minerals. Its typical appearance is metallic-lustrous, brass-yellow or brownish-yellow specks, not exceeding 0.4 mm in size. Due to its size and mode of occurrence, it is a mineral that can be identified almost exclusively by advanced laboratory techniques, such as electron microprobe analysis. ## Physical Properties This mineral is characterized by a metallic luster. It is opaque. Due to the microscopic size of the grains, properties such as hardness, density, cleavage, or fracture have not been precisely determined. ## Colors and Varieties It is observed in brass-yellow to brownish-yellow color. No varieties of this mineral are distinguished. ## History and Name Tellurohauchecornite was first described in 1980 by D.C. Harris, D.R. Owens, and J.M. Gait. Its name refers to its chemical composition – the presence of tellurium – and its structural similarity to the mineral hauchecornite. It was approved as a new mineral by the International Mineralogical Association (IMA) in 1979 (IMA1979-057). The type material, on which the mineral was described, comes from the Vermilion mine in the Sudbury district, Canada, and is stored at the Royal Ontario Museum and in the collections of the Geological Survey of Canada. ## Uses Tellurohauchecornite has no industrial or commercial application. Its significance is purely scientific and as a collector's item, as an extremely rare component of some ore deposits.

Properties

Mohs hardness: 4
Color: Bronze
Luster: Metallic
Streak: Black
Density: 0
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Identifying tellurohauchecornite in practice is impossible without specialized equipment. Recognition relies on optical analysis in reflected light under a ore microscope, where it exhibits characteristic colors and anisotropy. Final confirmation requires chemical analysis using an electron microprobe (EDS/WDS) to determine the composition (presence of nickel, bismuth, tellurium, and sulfur in appropriate proportions). ## Distinguishing from Similar Minerals It can be confused with other fine, metallic sulfides, tellurides, or arsenides, such as chalcopyrite, pentlandite, hauchecornite, tellurobismuthite, or parkerite. Differentiation relies solely on precise analysis of chemical composition and optical properties in reflected light. Hauchecornite, its close relative, does not contain tellurium in significant quantities. ## Crystal Forms Tellurohauchecornite occurs as anhedral, irregular grains, usually 10 to 400 micrometers in size, embedded in other minerals (most commonly in chalcopyrite or pentlandite). No well-formed crystals have been observed.

Geological environment

## Genesis Tellurohauchecornite is a hydrothermal mineral, associated with nickel and copper sulfide deposits. It forms in the late stages of ore crystallization, under conditions of elevated tellurium activity. Its presence indicates specific geochemical conditions prevailing during the formation of the deposit. ## Mineral Associations This mineral most commonly co-occurs with chalcopyrite, pentlandite, millerite, native gold, hessite, altaite, merenskyite, tellurobismuthite, kotulskite, sobolevskite, clausthalite, parkerite, and sphalerite. It is usually found as inclusions within chalcopyrite or pentlandite. ## Localities The most important and confirmed occurrences of tellurohauchecornite worldwide include: * **Canada:** Vermilion Mine, Sudbury District, Ontario (type locality). * **Russia:** Oktyabrskoye copper-nickel deposit, Talnakh area, near Norilsk in Siberia. * **China:** Jinchuan nickel deposit, Gansu Province.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a tellurohauchecornite specimen is assessed quite differently than for macroscopic minerals. Since the mineral is microscopic, the most important criterion is the abundance and size of grains visible under a microscope on a polished sample surface (a "polished section"). A specimen gains value if the tellurohauchecornite is well-defined and occurs in association with other rare minerals. Certainty of identification, supported by chemical analysis, and accurate locality documentation are also crucial. ## Popular Localities Specimens come exclusively from a few specialized localities. The most "classic" samples, including the type material, originate from the Vermilion mine in Canada. Specimens from Norilsk, Russia, are also scientifically significant.

Care and storage

## Cleaning Specimens containing tellurohauchecornite, due to their microscopic nature and embedding in the rock matrix, generally do not require and should not be subjected to cleaning. Any attempt at mechanical or chemical cleaning may destroy the fine mineral grains. If necessary, dust can be removed with a gentle stream of compressed air. ## What to Avoid Avoid contact with any chemicals, acids, and ultrasonic cleaners. Do not heat the specimen or expose it to rapid temperature changes. Protect it from scratching and impacts that could damage the delicate rock matrix. ## Storage Specimens should be stored under stable conditions, in a sealed "micromount" box, to protect them from dust and mechanical damage. A label with precise location and identification is crucial, as the mineral is invisible to the naked eye.

External references

https://www.mindat.org/min-3898.html