Nevskite
Chemical formula: Bi(Se,S)
A small, metallic bismuth, selenium, and sulfur mineral, forming tiny platy crystals in quartz veins.
Properties
- Mohs hardness
- 3
- Color
- Lead-gray
- Luster
- Metallic
- Streak
- Greyish-black
- Density
- 0
- Cleavage
- <mi>{0001}</mi>
- Fracture
- Micaceous
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Identifying nevskite in the field or in a collection is practically impossible without specialized equipment. Identification requires advanced analytical methods, such as scanning electron microscopy (SEM) with chemical composition analysis (EDS/WDS) and X-ray diffraction (XRD). A visual characteristic under high magnification is fine, hexagonal lamellae with a metallic luster. ## Distinguishing from Similar Minerals Nevskite can be confused with many other small, metallic bismuth minerals, such as native bismuth, joseite, tetradymite, or pilsenite. Visual differentiation is unreliable. Only chemical analysis, which will show the presence of bismuth, selenium, and sulfur in appropriate proportions, provides certain identification. ## Crystal Forms Nevskite forms very small, thin, platy or lamellar crystals with a hexagonal or trigonal outline. It also occurs as scaly and lamellar aggregates.
Geological environment
## Genesis Nevskite is a hydrothermal mineral. It forms in quartz-sulfide veins that cut granodiorites. Its formation is associated with crystallization from solutions rich in bismuth, selenium, and sulfur in the final stages of hydrothermal processes. ## Mineral Associations This mineral co-occurs with native bismuth, pilsenite, ikunolite, laitakarite, tetradymite, pyrite, chalcopyrite, sphalerite, galena, and quartz. ## Localities The only known and confirmed occurrence of nevskite in the world (type locality) is the Nevskoye (or Nevskoe) deposit in the Magadan Oblast in the Russian Far East.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a nevskite specimen primarily depends on its unambiguous identification and confirmation by analysis. Since the crystals are microscopic, their individual form or "purity" is not the main criterion. The most valuable specimens are those where nevskite forms richer concentrations or occurs in association with other rare bismuth minerals, and the whole is well-embedded in the rock matrix. ## Popular Localities The only source of nevskite specimens is its type locality – the Nevskoye deposit in Russia. All specimens available on the collector's market (though extremely rarely) come from this single location.
Care and storage
## Cleaning Due to its extreme rarity and small size, nevskite specimens generally do not require cleaning and should be left in their untouched state. Any intervention risks damaging the mineral. If cleaning is absolutely necessary, compressed air can be used to remove dust. ## What to Avoid Avoid any contact with chemicals, acids, and bases. The mineral is very soft (Mohs hardness 2), so avoid any touching, rubbing, and contact with harder objects. It should not be heated or exposed to sudden temperature changes. ## Storage Nevskite specimens should be stored exclusively in specialized "micromount" boxes, protected from shocks, dust, and moisture. It is best to keep them in stable room conditions, away from direct sunlight and heat sources.