Arsenowagnerite

Chemical formula: Mg<sub>2</sub>As<sup>5+</sup>O<sub>4</sub>F

An extremely rare magnesium and fluorine arsenate of the wagnerite group, discovered in volcanic exhalation products in Kamchatka.

## Characteristics Arsenowagnerite is the arsenate analogue of wagnerite. It occurs as very small, irregular or poorly formed grains, rarely exceeding 0.2 mm in size. It typically forms colorless, white, pale yellow, or greenish-yellow aggregates. Due to the small size of the crystals, its macroscopic features are difficult to observe, and most specimens appear as fine coatings or impregnations in the host rock. ## Physical Properties The mineral is transparent and exhibits a vitreous luster. Its Mohs hardness is approximately 5, and its calculated density is 3.75 g/cm³. It is a brittle mineral with a conchoidal fracture. ## Colors and Varieties Observed colors include colorless, white, pale yellow, and greenish-yellow. No color or commercial varieties are distinguished. ## History and Name The name arsenowagnerite refers to its chemical composition (dominance of arsenic over phosphorus) and its structural relationship to wagnerite. The mineral was approved by the International Mineralogical Association (IMA) in 2005. It was discovered in the Arsenatnaya fumarole on Tolbachik volcano (Kamchatka, Russia). ## Applications Arsenowagnerite has no industrial applications. It is solely an object of scientific and collecting interest as a very rare mineral with a specific genesis.

Properties

Mohs hardness
5
Luster
Vitreous
Streak
White
Density
3.75
Cleavage
Good on {010}
Fracture
Conchoidal
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of arsenowagnerite based on visual characteristics is impossible. Due to its occurrence as microscopic grains in complex parageneses, the only reliable method of identification is advanced chemical analysis (e.g., EDS/WDS) and structural analysis (X-ray diffraction, XRD). ## Distinguishing from Similar Minerals Arsenowagnerite is visually indistinguishable from many other colorless or pale yellow arsenates and sulfates occurring in the same paragenesis (e.g., anhydrite, dmisokolovite, svabite). The most difficult distinction is from wagnerite, which requires precise determination of the arsenic to phosphorus ratio. ## Crystal Forms It forms anhedral (irregular) to subhedral (poorly formed) grains, usually less than 0.2 mm in size. Sometimes it occurs as granular aggregates or coatings.

Geological environment

## Genesis Arsenowagnerite is a mineral of volcanic origin, crystallizing directly from gases (sublimates) in high-temperature fumaroles. It forms at temperatures of 500-600°C in an arsenic- and fluorine-rich environment. ## Mineral Associations This mineral co-occurs with other products of volcanic exhalations. In the type locality, it was found in association with hematite, tenorite, cassiterite, fluorophlogopite, anhydrite, sanidine, sylvite, and other rare arsenates, such as johillerite, dmisokolovite, akhtarandite, and svabite. ## Localities The only confirmed occurrence of arsenowagnerite 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, Tolbachik volcano, Kamchatka, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of arsenowagnerite collector specimens is primarily assessed based on the abundance of the mineral on the rock matrix and the presence of well-defined, albeit still microscopic, aggregates. Analytically confirmed specimens, as well as those co-occurring with other rare minerals from this locality, are highly valued. Color and transparency are of secondary importance due to the microscopic size of the grains. ## Popular Localities The only source of arsenowagnerite specimens is its discovery site on Tolbachik volcano in Kamchatka. Material from this locality is extremely rare and sought after by specialized collectors of systematic minerals and micromounts.

Care and storage

## Cleaning Arsenowagnerite specimens are typically micromounts, which are extremely delicate. Cleaning is not recommended. If necessary, a gentle stream of compressed air can be used to remove dust. Avoid contact with water and any chemical agents. ## What to Avoid The mineral is sensitive to mechanical shock and abrasion. Ultrasonic cleaners, acids, detergents, and sudden temperature changes should be strictly avoided. Store away from moisture. ## Storage Specimens should be stored exclusively in specialized micromineral boxes (micromounts) to protect them from mechanical damage, dust, and moisture. Storage under stable room conditions is recommended.

Sources

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