Aleutite

Chemical formula: [Cu<sup>2+</sup><sub>5</sub>O<sub>2</sub>](As<sup>5+</sup>O<sub>4</sub>)(V<sup>5+</sup>O<sub>4</sub>)·(Cu<sup>2+</sup><sub>0.5</sub>&#9744;<sub>0.5</sub>)Cl

Aleutite is an extremely rare copper arsenate-vanadate, forming dark green, tabular crystals in volcanic fumaroles.

## Characteristics Aleutite is a complex copper arsenate and vanadate with a characteristic dark green to greenish-black color. It occurs as small, tabular or prismatic crystals, often forming radial, fan-shaped, or chaotic aggregates and crusts. Individual crystals rarely exceed 1 mm in length. The mineral is opaque, becoming translucent only in very thin fragments, revealing an intensely green color. ## Physical Properties Its Mohs hardness is approximately 4. It has a vitreous luster, and on fracture surfaces, it can be slightly resinous. The density calculated based on the chemical formula and unit cell parameters is approximately 4.95 g/cm³. The streak of the mineral is greenish-gray. ## Colors and Varieties This mineral does not exhibit color variation. Its only known form consists of specimens ranging from dark green to almost black. No varieties have been distinguished. ## History and Name Aleutite was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2017. Its name comes from the Aleuts, the indigenous people of the Aleutian Islands, located near the discovery site. It was found in the exhalation products of volcanic fumaroles at Arsenatnaya on Tolbachik volcano in Kamchatka, Russia. ## Uses Due to its extreme rarity, small crystal size, and occurrence in a single, hard-to-reach location in the world, aleutite has no practical applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals.

Properties

Mohs hardness
4
Luster
Vitreous
Streak
Greenish-grey
Density
4.95
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Characteristic features of aleutite include its dark green to black color, vitreous luster, specific form of small, tabular crystals forming aggregates, and unique occurrence environment. Its genesis – as a product of crystallization from volcanic gases in fumaroles – is crucial for identification. ## Distinguishing from Similar Minerals Aleutite can be confused with other dark green or black minerals found in the fumaroles of Tolbachik volcano, such as lammerite, belloite, or some copper arsenates. Due to visual similarity and co-occurrence, definitive differentiation is possible almost exclusively using advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Crystal Forms Aleutite forms thin, tabular crystals with hexagonal or rhombic outlines, as well as prismatic crystals. They most often occur as radial or tangled aggregates, and also as fine crusts on volcanic rocks.

Geological environment

## Genesis Aleutite is a secondary mineral that forms through sublimation from hot volcanic gases. It crystallizes in high-temperature zones (above 450°C) and oxidizing conditions within active volcanic fumaroles. ## Mineral Associations This mineral occurs in association with other rare volcanic exhalation products. It is most often accompanied by: tenorite, hematite, euchlorine, lammerite, belloite, avdoninite, as well as other complex arsenates and sulfates. ## Locations The only confirmed location of aleutite in the world is its type locality – the Arsenatnaya fumarole, located on the second cinder cone of the North Breakthrough of the Great Fissure Eruption of Tolbachik volcano on the Kamchatka Peninsula in Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The most highly prized aleutite specimens are those with well-formed, visible-to-the-naked-eye crystals forming aesthetic, radial aggregates on a small rock matrix. Due to its extreme rarity, any specimen with distinct crystals is considered exceptional. Co-occurrence with other rare minerals from this locality adds additional value. ## Popular Localities Collector specimens come exclusively from one location in the world – Tolbachik volcano in Kamchatka. Material from this locality is very limited and rarely appears on the market.

Care and storage

## Cleaning Aleutite specimens should only be dry-cleaned, using a soft brush or compressed air to remove dust. Any contact with water and other liquids should be avoided, as it may be unstable or damaged as a fumarolic product. ## What to Avoid This mineral is potentially sensitive to moisture, sudden temperature changes, and chemicals, especially acids. Ultrasonic cleaners or steam cleaning should not be used. It should be protected from direct sunlight, which can cause its degradation. ## Storage It is recommended to store aleutite in stable, dry conditions. The best solution is to place the specimen in a sealed, lidded "perky box" to protect it from dust, moisture, and mechanical damage.

External references

Sources

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