Kozyrevskite

Chemical formula: Cu²⁺₄O(As⁵⁺O₄)₂

Kozyrevskite is a rare copper arsenate with an intensely green color, occurring as small, tabular crystals in volcanic fumaroles.

## Characteristics Kozyrevskite is a copper oxyarsenate, forming characteristic, small crystals with a tabular or bladed habit. They typically occur as radial or chaotic aggregates, and individual crystals rarely exceed 0.3 mm in length. This mineral is distinguished by its vivid, grass-green color, which can transition into lighter, yellowish-green hues. ## Physical Properties Kozyrevskite crystals are transparent and exhibit a vitreous luster. The mineral's hardness on the Mohs scale is 3.5, classifying it as a relatively soft material. Its density is high, at 4.934 g/cm³. ## Colors and Varieties This mineral occurs in uniform, light-green shades, ranging from grass-green to yellowish-green. No color varieties or commercial varieties have been distinguished. ## History and Name Kozyrevskite was first described in 2012. Its name honors Aleksey Aleksandrovich Kozyrev (1944–1991), a Russian volcanologist who for many years conducted research on the Tolbachik volcano in Kamchatka – the mineral's discovery site. ## Uses Due to its extreme rarity and small crystal size, kozyrevskite has no industrial applications. It is solely an object of scientific and collecting interest for specialists who collect microscopic minerals (so-called "micromounts").

Properties

Mohs hardness
3.5
Luster
Vitreous
Streak
White
Density
4.934
Cleavage
(100) and (001) perfect
Fracture
Step-Like
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Kozyrevskite can be identified by its characteristic, light-green color, tabular crystal habit, and specific occurrence environment – as a sublimation product in volcanic fumaroles. The luster is vitreous, and the crystals are transparent. ## Distinguishing from Similar Minerals It can be confused with other secondary copper arsenates, such as euchroite or leningradite, which also occur in Tolbachik fumaroles. Definitive differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS), due to visual similarity and co-occurrence. ## Crystal Forms It forms thin, tabular or bladed crystals, elongated along the [010] axis and flattened parallel to {100}. Crystals often form radial or irregular aggregates on the surface of the host rock.

Geological environment

## Genesis Kozyrevskite is a mineral of volcanic origin, formed by sublimation from volcanic gases in an environment rich in arsenic and copper. It crystallizes in high-temperature (above 450°C) exhalative fumaroles, depositing directly on porous basaltic crust. ## Mineral Associations This mineral co-occurs with other rare arsenates and sulfates formed under similar conditions. The most common associated minerals include: tenorite, hematite, euchroite, leningradite, johillerite, ericlaxmanite, arsmirandite, and lammerite. ## Localities The only confirmed locality of kozyrevskite in the world is its type locality: Arsenatnaya fumarole on Tolbachik volcano on the Kamchatka Peninsula, Russia.

Rarity

Very rare

For collectors

## Quality Criteria The collecting appeal of kozyrevskite specimens depends on the richness and aesthetics of the crystal aggregates on the rock matrix. Most valued are specimens with well-formed, undamaged crystals of intense, grass-green color, forming visually attractive groups. The contrast with the dark host rock also enhances aesthetic value. ## Popular Localities All known collector specimens come from a single location in the world – the fumarole of Tolbachik volcano in Kamchatka. Material from this locality is extremely rare and sought after by specialized micromount collectors.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the small size and delicacy of the crystals, contact with water, and especially with ultrasonics, is absolutely not recommended. ## What to Avoid Avoid contact with all chemicals, especially acids, which can rapidly dissolve the mineral. The crystals are brittle and susceptible to mechanical damage. They should be protected from moisture and sudden temperature changes. ## Storage Kozyrevskite specimens, typically in the form of "micromounts," should be stored under stable conditions, in closed, padded "micromount boxes." Protect from dust, moisture, and direct sunlight.

External references

Sources

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