Borisenkoite

Chemical formula: Cu<sup>2+</sup><sub>3</sub>[(V<sup>5+</sup>,As<sup>5+</sup>)O<sub>4</sub>]<sub>2</sub>

Borisenkoite is a rare vanadate mineral, a copper vanadate with arsenic admixture, forming small, platy crystals.

## Characteristics Borisenkoite is a very rare mineral belonging to the vanadate group, chemically classified as a copper vanadate with a significant content of arsenic substituting for vanadium. It occurs as very small, thin, platy crystals, rarely exceeding 0.2 mm. These crystals form aggregates or rosettes. Due to their size, its visual features are difficult to observe without magnification. ## Physical Properties Borisenkoite crystals exhibit a vitreous luster. They are brittle, and their hardness and density have not been precisely determined due to the small size of the samples. ## Colors and Varieties This mineral is characterized by a dark green color. No varieties have been distinguished. ## History and Name Borisenkoite was discovered in volcanic exhalation products (fumaroles) at Tolbachik volcano in Kamchatka, Russia. It was approved as a new mineral by the International Mineralogical Association (IMA) in 2017. Its name honors Lev Fedorovich Borisenko (1925-2015), a Russian geologist and mineralogist, a specialist in vanadium, titanium, and scandium deposits, who worked at the Institute of Mineralogy, Geochemistry, and Crystal Chemistry of Rare Elements (IMGRE) in Moscow. ## Applications Borisenkoite has no industrial applications. It is solely an object of scientific and collecting interest due to its extreme rarity and specific formation environment.

Properties

Luster
Vitreous
Streak
Green
Cleavage
Perfect on {001}
Transparency
Translucent
Crystal system
Triclinic

Diagnostic features

## Identification Amateur identification of borisenkoite is practically impossible. Identification requires advanced analytical methods, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS). A preliminary indication may be its dark green color, platy crystal habit, and occurrence in volcanic fumarole products. ## Distinguishing from Similar Minerals Borisenkoite can be confused with other rare, green secondary minerals from the vanadate or arsenate groups of copper, which occur in the same environment, e.g., with lammerite, eriostoranite, or popovite. Definitive distinction is only possible based on chemical and crystallographic analysis. ## Crystal Forms It forms very small, thin, platy crystals, often grouped into rosette-like or radial aggregates. Single crystals are rare.

Geological environment

## Genesis Borisenkoite is a mineral of volcanic origin, crystallizing from gases (exhalations) in active fumarole zones. It forms as a result of sublimation at temperatures of approximately 150-250°C in an environment rich in copper, vanadium, and arsenic. ## Mineral Associations This mineral co-occurs with other volcanic exhalation products, such as hematite, tenorite, eriostoranite, lammerite, popovite, chalcanthite, belloite, and atlasovite. ## Localities The only confirmed locality of borisenkoite in the world is its type locality - Yadovitaya fumarole on the second cinder cone of the Northern Breakthrough of the Great Fissure Eruption of Tolbachik volcano in Kamchatka, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a borisenkoite specimen primarily depends on the abundance and development of crystals on the rock matrix. Specimens with distinct, well-formed crystal aggregates contrasting with the substrate are most valued. Due to the microscopic size of the crystals, the aesthetics of the entire cluster, rather than a single crystal, is key. ## Popular Localities The only source of specimens is the type locality at Tolbachik volcano in Kamchatka. Material from this location is extremely rare and available almost exclusively in specialized collections and research institutions.

Care and storage

## Cleaning Due to the extreme brittleness and small size of the crystals, mechanical cleaning is not recommended. Specimens should be protected from dust by storing them in sealed containers. If cleaning is absolutely necessary, compressed air can be used from a safe distance. ## What to Avoid Avoid contact with water, chemicals, as well as any vibrations and impacts. The crystals are very delicate and easily damaged or detached from the substrate. ## Storage It is recommended to store borisenkoite specimens exclusively in specialized, sealed "micromount" boxes, which protect them from mechanical damage and dust. Avoid exposure to changes in humidity and temperature.

Sources

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