Wrightite

Chemical formula: K₂Al₂O(As⁵⁺O₄)₂

Wrightite is a rare potassium aluminum arsenate, forming colorless to pale yellow, tabular crystals, discovered in volcanic products on Kamchatka.

## Characteristics Wrightite is a potassium aluminum arsenate, occurring as small, transparent crystals. It typically forms thin, tabular crystals with a hexagonal outline, which can combine into rosette-like or fan-shaped aggregates. Its maximum observed size is approximately 0.2 x 0.2 x 0.02 mm. It is a brittle mineral. ## Physical Properties Wrightite crystals are characterized by a vitreous luster. Due to the small size of the crystals, many physical properties, such as hardness, have not been precisely determined. The density calculated based on the formula and unit cell parameters is 3.499 g/cm³. ## Colors and Varieties Wrightite is colorless to pale yellow. No varieties have been distinguished. ## History and Name The mineral was named in honor of Frederick Eugene Wright (1877–1953), an American mineralogist and optician from the Carnegie Institution in Washington, who made significant contributions to the development of ore microscopy methods. Wrightite was recognized as a new mineral species by the IMA in 2013, although its discovery dates back to 1983. ## Uses Wrightite has no industrial application and is of purely scientific and collector's interest as a rare mineral.

Properties

Luster
Vitreous
Streak
White
Density
3.499
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of wrightite is possible almost exclusively using advanced analytical methods, such as Raman spectroscopy or X-ray diffraction, due to its small size and occurrence in complex parageneses. Visually, it is characterized by thin, tabular crystals with a hexagonal outline. ## Distinguishing from similar minerals It can be confused with other colorless or pale yellow secondary minerals found in fumaroles, such as other arsenates (e.g., johillerite, dmisokolovite). Definitive differentiation requires specialized chemical and structural analysis. ## Crystal forms Wrightite crystallizes as thin, tabular crystals, often with a hexagonal outline. These crystals form fan-shaped or rosette-like aggregates on the surface of the host rock.

Geological environment

## Genesis Wrightite is a fumarolic mineral. It forms as a result of the sublimation of volcanic gases at high temperatures (around 600°C) in an oxidizing environment. It crystallizes directly from the gas phase on the surfaces of porous basaltic lava crusts. ## Mineral associations This mineral co-occurs with other rare arsenates and sulfates formed under similar conditions. In its type locality, it was found in association with hematite, tenorite, johillerite, dmisokolovite, shchurovskyite, anaphite, langbeinite, and arcanite. ## Localities The only confirmed locality of wrightite in the world is its type locality in Russia - the second cinder cone formed during the Great Fissure Eruption of Tolbachik volcano on Kamchatka.

Rarity

Very rare

For collectors

## Quality criteria As a "micromount" mineral, the quality of a specimen is primarily determined by the abundance and development of crystals on the rock matrix, as well as the presence of associated minerals. The most desirable specimens are those with clearly formed, rosette-like aggregates of transparent crystals, contrasting with the darker host rock. ## Popular localities The only source of wrightite specimens is its type locality at Tolbachik volcano on Kamchatka, Russia. Material from historical eruptions is very limited and rarely appears on the market.

Care and storage

## Cleaning Due to the extreme rarity, brittleness, and small size of the crystals, mechanical cleaning is not recommended. Specimens should be protected from dust in their original containers. ## What to avoid Avoid contact with chemicals, acids, and water. The crystals are very delicate and susceptible to mechanical damage. They should be protected from vibrations and shocks. ## Storage Wrightite specimens are best stored in stable, sealed "micromount" containers that protect against dust, moisture, and physical damage. Display should be away from sources of vibration.

External references

Sources

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