Averievite

Chemical formula: Cu₂+₅O₂(V₅+O₄)₂·Cu₂+Cl₂

Averievite is a very rare mineral from the vanadate group, found as dark green to black coatings and crystals in volcanic fumaroles.

## Characteristics Averievite is a complex copper oxyvanadate with chlorine, occurring as very fine, tabular or prismatic crystals, rarely exceeding 0.2 mm. It forms granular aggregates, rosette-like clusters, and most often appears as crusts and coatings on volcanic rocks. Its color is typically dark green, olive green to almost black. ## Physical Properties Averievite crystals exhibit a vitreous luster. The mineral is translucent to opaque. Due to the small size of the crystals, precise determination of hardness and density is difficult; the calculated density is approximately 4.45 g/cm³. ## Colors and Varieties This mineral has no known varieties. Its coloration is uniform, ranging from dark green through olive green to black. The streak of the mineral is greenish-gray. ## History and Name The mineral is named in honor of Vladimir Viktorovich Averiev (Владимир Викторович Авeрьев, 1905–1967), a Russian volcanologist who studied geothermal activity in Kamchatka. Averievite was first described in 1997 by L.P. Vergasova, S.K. Filatov, T.F. Semenova, and V.V. Ananiev based on samples from Tolbachik volcano in Kamchatka, Russia. ## Uses Due to its extreme rarity and microscopic size, averievite has no industrial applications. It is solely an object of scientific and collecting interest for specialized collectors of rare minerals.

Properties

Luster: Vitreous
Streak: Greenish-gray
Density: 4.45
Cleavage: None
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Trigonal

Diagnostic features

## Identification Amateur identification of averievite is practically impossible. It requires advanced analytical methods such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). Preliminary identification is based on its characteristic occurrence (volcanic fumaroles), dark green color, and association with other rare exhalative minerals. ## Distinguishing from Similar Minerals It can be confused with other green or black volcanic exhalation products, such as tenorite, atacamite, paratacamite, or other copper vanadates (e.g., stoiberite, ziesite). Definitive differentiation is possible only through laboratory analysis. ## Crystal Forms Crystals are very small, usually tabular or short-prismatic. They form granular aggregates, rosettes, and thin crusts and coatings.

Geological environment

## Genesis Averievite is an exhalative mineral. It forms as a result of the sublimation of volcanic gases in high-temperature fumaroles (above 600°C), where hot gases rich in vanadium, copper, and chlorine react with atmospheric oxygen and deposit on the surface of volcanic rocks, mainly basalts. ## Mineral Associations It co-occurs with other fumarolic minerals such as hematite, tenorite, lammerite, leningradite, ponomarevite, stoiberite, shcherbinaite, ziesite, and coprochroit. ## Localities The only confirmed and type locality for averievite in the world is the Tolbachik volcanic complex on the Kamchatka Peninsula in Russia, specifically the fumaroles formed after the Great Fissure Eruption of 1975-1976.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of averievite specimens is primarily assessed based on the richness of the coating on the host rock and the presence of well-formed, albeit microscopic, crystals. Due to the nature of the mineral, specimens are almost always micromounts. Samples with well-documented associations of other rare minerals from the same locality are highly valued. ## Popular Localities The sole source of averievite specimens is Tolbachik volcano in Kamchatka. Material from this locality is extremely difficult to acquire and appears on the collector's market sporadically, mainly through specialized dealers dealing with minerals from this part of the world.

Care and storage

## Cleaning Averievite specimens are extremely delicate and usually occur as thin coatings on the host rock. Mechanical or chemical cleaning is not recommended. If necessary, compressed air (from a safe distance) can be used to remove dust. ## What to Avoid Contact with water, acids, and other chemicals, which can destroy microscopic crystals, must be absolutely avoided. The mineral is sensitive to shocks and abrasions. It should be protected from changes in temperature and humidity. ## Storage Specimens should be stored in stable conditions, preferably in tightly sealed "micromount" boxes, which protect against dust, moisture, and mechanical damage. Light exposure is not considered harmful, but storage in darkness is recommended.

Sources

IMA Mineral List (CNMNC)