Kuramite
Chemical formula: Cu<sup>1+</sup><sub>2</sub>Cu<sup>2+</sup>Sn<sup>4+</sup>S<sup>2-</sup><sub>4</sub>
Kuramite is a rare copper tin sulfide, forming tiny, metallic grains, originally discovered in Uzbekistan.
Properties
- Mohs hardness
- 4-5
- Luster
- Metallic
- Streak
- Black
- Density
- 4.59
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Tetragonal
Diagnostic features
## Identification Identification of kuramite is impossible without advanced laboratory techniques. It requires analysis by electron microprobe (EDS/WDS) or X-ray diffraction (XRD) to confirm its chemical composition and crystal structure. In reflected light microscopy, it is grayish-brown and shows weak anisotropy. ## Distinguishing from Similar Minerals Macroscopically, it is impossible to distinguish from other dark sulfides with which it coexists, such as stannite, kesterite, or briartite. It differs from them subtly in chemical composition (mainly the ratio of copper, zinc, iron, and tin), which can only be determined by chemical analysis. ## Crystal Forms Kuramite forms very fine, anhedral (irregular) grains, usually less than 0.1 mm in diameter. Poorly developed, rounded crystal forms are rarely observed. It usually occurs as aggregates or intergrowths with other minerals.
Geological environment
## Genesis Kuramite is a hydrothermal mineral. It forms in quartz-sulfide veins associated with subvolcanic intrusions. At its type locality (Kairagach, Uzbekistan), it is associated with mineralized zones in andesites and dacites. ## Mineral Associations It most commonly coexists with stannite, kesterite, chalcopyrite, galena, sphalerite, tetrahedrite, tennantite, arsenopyrite, pyrite, native gold, and quartz. ## Localities The most important and confirmed kuramite localities worldwide include: - **Uzbekistan**: Kairagach gold deposit in the Kurama Mountains (type locality). - **Japan**: Akenobe Mine in Hyōgo Prefecture. - **Slovakia**: Banská Štiavnica deposit. - **Argentina**: Capillitas deposit in Catamarca Province. - **Canada**: Kidd Creek Mine in Ontario.
Rarity
Very rare
For collectors
## Quality Criteria In the case of such a rare mineral as kuramite, the primary criterion for value is the mere confirmation of its presence on a specimen through analysis. Collectible specimens are typically fragments of host rock with microscopic, identified kuramite grains. Samples where the grains are relatively "rich" or coexist with other rare minerals are more highly valued. The size or aesthetics of the kuramite grain itself plays virtually no role due to its microscopic nature. ## Popular Localities The most sought-after by specialized collectors are specimens from the type locality – the Kairagach deposit in Uzbekistan. Material from other confirmed localities, such as the Akenobe mine in Japan or Kidd Creek in Canada, is also valued.
Care and storage
## Cleaning Kuramite specimens occur as microscopic inclusions in the host rock and do not require cleaning. Any attempt at mechanical or chemical cleaning may damage the delicate mineral grains. ## What to Avoid Avoid contact with chemicals, especially acids, which can react with sulfides. Also, avoid ultrasonic cleaners and sudden temperature changes. ## Storage Specimens containing kuramite are best stored under stable conditions, in their original "micromount" box, protecting them from dust, moisture, and mechanical damage. It is not sensitive to light.