Edtollite

Chemical formula: K₂NaCu²⁺₅Fe³⁺O₂(As⁵⁺O₄)₄

Edtollite is a rare copper, iron, sodium, and potassium arsenate, forming small, tabular crystals of a dark green color and vitreous luster.

## Characteristics Edtollite is a very rare mineral from the arsenate group, with a complex chemical composition including potassium, sodium, copper, and iron. It occurs as very small, tabular or bladed crystals, rarely exceeding 0.2 mm in length. These crystals often form rosette-like or radial aggregates. Due to their size, visual features are difficult to observe without magnification. ## Physical Properties Edtollite crystals exhibit a vitreous luster. They are brittle, and their hardness and density have not been precisely measured due to the small size of the samples. The mineral is transparent to translucent. ## Colors and Varieties Edtollite has a characteristic dark green color. It does not exhibit pleochroism. No varieties are known. ## History and Name The mineral was named after Edward (Ed) Toller (born 1969), an American mineral collector from Tucson, Arizona, who specializes in minerals from Tolbachik volcano and provided the material for research in which edtollite was discovered. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2010 (IMA2010-044). It was described by Russian scientists, including Igor V. Pekov and Natalia V. Zubkova. ## Uses Edtollite has no industrial application. It is solely an object of scientific and collecting interest, sought after by collectors specializing in rare minerals or minerals from Tolbachik volcano.

Properties

Color
Brown–black to black
Luster
Vitreous
Streak
Green
Density
4.26
Cleavage
Perfect on {001}
Fracture
Brittle
Transparency
Transparent to Translucent
Crystal system
Triclinic

Diagnostic features

## Identification Field identification of edtollite is impossible. Identification requires advanced laboratory methods, such as chemical analysis (EDS) and X-ray diffraction (XRD). In a collection, it can be preliminarily identified based on its characteristic appearance (dark green, tabular crystals in aggregates) and, most importantly, its locality – it occurs exclusively in the fumaroles of Tolbachik volcano. ## Distinguishing from Similar Minerals It can be confused with other green copper arsenates found in the same environment, such as lammerite, eriostranite, or popovite. Definitive distinction is only possible through chemical and crystallographic analysis. ## Crystal Forms Edtollite forms thin, tabular or bladed crystals, elongated along one of the axes. These crystals often combine into radial, stellate, or rosette-like aggregates.

Geological environment

## Genesis Edtollite is a mineral of volcanic origin, formed by sublimation from volcanic gases in high-temperature fumaroles. It crystallizes in exhalation zones, where hot gases rich in arsenic, copper, and other elements react with the surrounding rocks. ## Mineral Associations This mineral occurs in association with other rare arsenates and sulfates formed under similar conditions. It co-occurs with tenorite, hematite, aphthitalite, langbeinite, sanidine, eriostranite, lammerite, popovite, arsmirandite, and others. ## Localities The only confirmed occurrence of edtollite in the world is its type locality: the Yadovitaya fumarole on the Second Scoria Cone of the North Breach of the Great Fissure Eruption of Tolbachik volcano in Kamchatka, Russia.

Rarity

Very rare

For collectors

## Quality Criteria The quality of an edtollite specimen primarily depends on the richness and size of the crystal aggregates on the matrix. The most prized specimens are those with clearly formed, rosette-like clusters of dark green crystals, contrasting well with the host rock. Due to the microscopic nature of the mineral, even small but well-formed aggregates are considered valuable. ## Popular Localities The only source of edtollite specimens is Tolbachik volcano in Kamchatka. Material from this locality is extremely difficult to obtain due to its remote and dangerous location, making every specimen a valuable acquisition for specialized collectors.

Care and storage

## Cleaning Due to its extreme rarity, small size, and brittleness of crystals, mechanical cleaning is not recommended. Specimens should be protected from dust in sealed containers. ## What to Avoid Avoid contact with chemicals, especially acids, which can damage the mineral. Ultrasonic and steam cleaning should also be avoided. The mineral is stable under normal conditions but should be protected from extreme temperatures. ## Storage Edtollite specimens, typically microscopic crystals on matrix, should be stored in specialized "micromount" boxes to prevent mechanical damage and dust accumulation. Vibrations and shocks should be avoided.

External references

Sources

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