Stibiocolusite

Chemical formula: Cu¹⁺₁₂Cu²⁺V³⁺(Sb⁵⁺,Sn⁴⁺,As⁵⁺)₃S²⁻₁₆

Stibiocolusite is a rare, dark gray sulfide of copper, vanadium, and antimony, occurring as fine grains in gold and copper deposits.

## Characteristics Stibiocolusite is a mineral from the germanite group, belonging to the sulfide class. It forms very fine, anhedral (irregular) grains, usually not exceeding 0.1 mm in size. It is rarely observed in the form of small, isolated crystals with tetrahedral outlines. It is opaque and has a dark gray color with a metallic luster. ## Physical Properties Its Mohs hardness is 4-4.5. It exhibits a conchoidal fracture. Due to the small size of the grains, precise determination of density is difficult, hence there is a lack of precise data on this subject. ## Colors and Varieties This mineral is uniform in color and occurs in shades of dark gray. No color or commercial varieties are distinguished. ## History and Name Stibiocolusite was first described in 1991. Its name refers to its chemical composition – a high content of antimony (Latin: *stibium*) and its structural similarity to colusite. It was approved as a new mineral by the International Mineralogical Association (IMA). ## Applications Stibiocolusite has no industrial application. It is of purely scientific and collector's interest as a rare mineral.

Properties

Mohs hardness
4-4.5
Luster
Metallic
Streak
Gray
Density
0
Fracture
Conchoidal
Transparency
Opaque
Crystal system
Isometric

Diagnostic features

## Identification Identification of stibiocolusite requires advanced laboratory techniques, such as chemical composition analysis using an electron microprobe (EDS/WDS) and X-ray diffraction (XRD) analysis. Preliminary identification under a reflected light microscope is based on its dark gray color and metallic luster. ## Distinguishing from Similar Minerals It can be confused with other sulfides of similar appearance, such as germanite, colusite, tetrahedrite, or tennantite. Definitive differentiation is possible only through chemical analysis, which will show the characteristic dominance of antimony and the presence of vanadium for stibiocolusite. ## Crystal Forms It most often occurs as irregular, rounded grains intergrown with other minerals. Rarely, it forms small, poorly developed crystals with a tetrahedral habit.

Geological environment

## Genesis Stibiocolusite forms under hydrothermal conditions. It is a component of epithermal gold-bearing and copper-bearing deposits, where it crystallizes alongside other sulfides and sulfosalts. ## Mineral Associations This mineral co-occurs with chalcopyrite, bornite, enargite, luzonite, tennantite, tetrahedrite, germanite, colusite, native gold, pyrite, and barite. ## Localities The most important and typical localities for stibiocolusite include: - Kairagach gold deposit in the Tashkent region, Uzbekistan. - Chelopech gold and copper mine in Bulgaria.

Rarity

Very rare

For collectors

## Quality Criteria As a microscopic mineral, stibiocolusite is not evaluated according to typical criteria such as crystal size or form. The collector's value of a specimen depends on the abundance of stibiocolusite grains in the host rock and on the confirmation of its identity through analysis. Samples from type localities are most highly prized. ## Popular Localities The most sought-after by specialized collectors are specimens from Kairagach in Uzbekistan and from the Chelopech mine in Bulgaria, as these are its discovery sites.

Care and storage

## Cleaning Stibiocolusite specimens, due to their microscopic size and occurrence within the host rock, usually do not require cleaning. If necessary, compressed air can be used to remove dust. ## What to Avoid Avoid contact with chemicals, especially acids, which can damage the mineral and the host rock. Ultrasonic or mechanical cleaning is not recommended due to the fragility and small size of the grains. ## Storage Specimens should be stored in stable conditions, away from dust and moisture, preferably in a sealed display box or cabinet. Due to their microscopic nature, they are often stored as microscopic preparations (thin sections).

External references

Sources

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