Stibiogoldfieldite
Chemical formula: Cu<sup>1+</sup><sub>6</sub>Cu<sup>1+</sup><sub>6</sub>(Sb<sup>3+</sup><sub>2</sub>Te<sup>4+</sup><sub>2</sub>)S<sup>2-</sup><sub>13</sub>
Stibiogoldfieldite is a very rare sulfosalt mineral, an antimony analog of goldfieldite, found as small, metallic grains.
Properties
- Mohs hardness
- 3-3.5
- Luster
- Metallic
- Streak
- Black
- Density
- 5.07
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Isometric
Diagnostic features
## Identification Identification of stibiogoldfieldite is impossible without advanced laboratory techniques. It requires chemical analysis (e.g., using an electron microprobe - EDS/WDS) to confirm the dominance of antimony over tellurium, and X-ray diffraction (XRD) analysis to confirm its crystal structure. In polished ore sections under a reflected light microscope, it appears gray. ## Distinguishing from Similar Minerals Stibiogoldfieldite is visually indistinguishable from other minerals of the tetrahedrite group, such as tetrahedrite, tennantite, goldfieldite, or arsenogoldfieldite. Differentiation relies solely on precise chemical analysis. ## Crystal Forms This mineral primarily forms anhedral (irregular) grains, typically not exceeding a few tens of micrometers in size. Poorly formed, small crystals with a tetrahedral habit, typical for minerals of its group, are rarely observed.
Geological environment
## Genesis Stibiogoldfieldite forms under hydrothermal conditions, in ore veins of medium and low formation temperatures. It is a product of crystallization from solutions rich in copper, sulfur, antimony, and tellurium. ## Mineral Associations It most often co-occurs with other minerals of the tetrahedrite group (goldfieldite, tetrahedrite), as well as with chalcopyrite, bornite, enargite, luzonite, pyrite, sphalerite, galena, and gold and silver tellurides (e.g., sylvanite, hessite). ## Localities The most important and confirmed occurrences of this very rare mineral are: - Kajaran (Kajaran) copper-molybdenum deposit in Syunik Province, Armenia (type locality). - Ozernovskoe deposit in Kamchatka, Russia. - Mohawk Mine in Goldfield, Esmeralda County, Nevada, USA.
Rarity
Very rare
For collectors
## Quality Criteria Stibiogoldfieldite specimens are not evaluated for aesthetic appeal, as the mineral occurs as microscopic grains. The collector and scientific value of a specimen lies in the confirmation of the mineral's presence through chemical analysis. The most valuable samples are those from the type locality (Kajaran) or rich associations with other rare sulfosalts and tellurides, where stibiogoldfieldite forms relatively "large" (on a micro-scale) and chemically pure grains.
Care and storage
## Cleaning Stibiogoldfieldite specimens, due to their microscopic nature and occurrence as inclusions in other minerals, are practically impossible to clean under amateur conditions. Any attempts at mechanical or chemical cleaning may destroy the delicate grains. ## What to Avoid Avoid contact with chemicals, especially acids, which can react with sulfides. Also, avoid ultrasound and high temperatures, which could damage the specimen or the entire rock matrix. ## Storage Specimens containing stibiogoldfieldite should be stored under stable conditions, in a dry place, away from direct sunlight and contaminants. It is best to store them in labeled collector boxes to prevent mechanical damage and identification errors.