Nicksobolevite

Chemical formula: Cu₂+₇(Se₄+O₃)₂O₂Cl₆

Nicksobolevite is an extremely rare copper, chlorine, and selenium mineral, forming microscopic, tabular crystals of an intense green color.

## Characteristics Nicksobolevite is a secondary mineral from the selenite group, occurring as very small, tabular or bladed crystals, which rarely exceed 0.3 mm in length. It forms thin, rosette-like or radial aggregates on rock surfaces. Its most characteristic features are its intense, emerald-green color and strong, vitreous luster. ## Physical Properties Crystals are very brittle. The Mohs hardness is low, at 2. The mineral exhibits strong pleochroism, changing color from yellowish-green to bluish-green depending on the observation direction. ## Colors and Varieties Nicksobolevite occurs in one characteristic color – emerald-green. No varieties have been distinguished. ## History and Name The mineral was discovered in volcanic exhalation products (fumaroles) at Tolbachik volcano in Kamchatka, Russia. It was approved by the International Mineralogical Association (IMA) in 2012. Its name honors the Russian geologist and petrologist, academician Nikolai Vladimirovich Sobolev (1935–2022), for his contributions to research on processes occurring deep within the Earth. ## Uses Due to its extreme rarity and microscopic size, nicksobolevite has no industrial applications. It is solely an object of scientific and collecting interest for specialized micromineral collectors.

Properties

Mohs hardness: 2
Luster: Vitreous
Streak: Green
Density: 4.16
Cleavage: Perfect on {100}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identifying nicksobolevite under amateur conditions is practically impossible and requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS). Preliminary identification can be based on its characteristic emerald-green color, the specific form of thin, tabular crystals forming rosette aggregates, and its co-occurrence with other selenites and copper chlorides in a volcanic fumarole environment. ## Distinguishing from Similar Minerals Nicksobolevite can be confused with many other green secondary copper minerals, such as georgbokiite, sofiite, ilinskite, or chloromenite, which occur in the same environment. Definitive distinction is only possible based on detailed crystallographic and chemical analysis. ## Crystal Forms The mineral forms very thin, tabular or bladed crystals, often flattened. These crystals combine into radial or rosette aggregates, and also form thin coatings and crusts.

Geological environment

## Genesis Nicksobolevite is a mineral of volcanic origin, crystallizing directly from hot gases (exhalations) in active fumarole zones. It forms at temperatures of approximately 150-200°C as a result of the reaction of volcanic gases rich in selenium, chlorine, and copper with atmospheric oxygen. ## Mineral Associations This mineral co-occurs with other rare volcanic sublimation products, such as sofiite, ilinskite, georgbokiite, chloromenite, cotunnite, halite, and hematite. ## Localities The only confirmed locality of nicksobolevite in the world is its type locality – the Yadovitaya fumarole on the second cone of the North Breach of the Great Fissure Eruption of Tolbachik volcano in Kamchatka, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to the microscopic nature of the mineral, the main criterion for evaluation is the quality and richness of the specimen as a whole. Samples with well-formed, sharp crystals forming aesthetic, rosette-like aggregates are most valued. Contrast with the rock matrix and the presence of associated minerals are also important. The intensity and purity of the emerald-green color also increase the specimen's value. ## Popular Localities All collector specimens come from a single location in the world – Tolbachik volcano in Kamchatka.

Care and storage

## Cleaning Nicksobolevite specimens are extremely delicate and usually too small to be safely cleaned mechanically. If cleaning is absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Any contact with water or other chemicals should be avoided. ## What to Avoid The mineral is potentially soluble in water and acids. Contact with any liquids must be strictly avoided. The crystals are very brittle, so they must be protected from shocks, impacts, and any touching. It should not be heated or exposed to temperature changes. ## Storage Specimens should be stored exclusively in specialized micromount boxes, which protect them from mechanical damage, dust, and moisture. Store in a dry place at a stable room temperature.

Sources

IMA Mineral List (CNMNC)