Bradaczekite

Chemical formula: NaCu<sup>2+</sup>Cu<sup>2+</sup>Cu<sup>2+</sup><sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>3</sub>

Bradaczekite is a rare sodium copper arsenate, forming dark green, tabular crystals, discovered in fumaroles of Tolbachik volcano.

## Characteristics Bradaczekite is a sodium copper arsenate, occurring as very small, tabular or platy crystals, rarely exceeding 0.3 mm in length. These crystals form aggregates and coatings on basaltic scoria. The mineral is characterized by its dark green color and vitreous luster. ## Physical Properties Bradaczekite crystals are brittle. Due to the small size of the crystals, precise determination of hardness and density was not possible. Density was calculated based on the chemical formula and unit cell parameters, and is approximately 4.99 g/cm³. ## Colors and Varieties This mineral occurs in a uniform, dark green color. No other color varieties or commercial forms have been observed. ## History and Name Bradaczekite was officially recognized as a new mineral by the International Mineralogical Association (IMA) in 2017 (IMA2017-026). The name honors Hans Bradaczek (born 1939), retired professor of crystallography at the Free University of Berlin, for his contributions to this field of science. The mineral was discovered in volcanic exhalation products. ## Uses Bradaczekite has no industrial applications. Its significance is purely scientific and as a collector's item, as a rare and recently discovered mineral species.

Properties

Luster
Vitreous
Streak
Green
Density
4.99
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of bradaczekite requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), due to its occurrence as microscopic crystals. Preliminary identification based on its dark green color, tabular habit, and specific occurrence environment (volcanic fumaroles) is possible but uncertain. ## Distinguishing from similar minerals Bradaczekite can be confused with other green copper arsenates found in the same environment, such as erythrosiderite, johillerite, or lammerite. Definitive differentiation is only possible through chemical and crystallographic analysis. ## Crystal forms Bradaczekite forms thin, tabular or platy crystals with an elongated habit, often with striations on the surfaces. These crystals occur as individual individuals or form irregular aggregates and coatings.

Geological environment

## Genesis Bradaczekite is a mineral of volcanic origin. It forms as a result of crystallization from gases (exhalations) in active fumaroles, at temperatures reaching 500-600°C. It crystallizes on the surface of porous, basaltic scoria. ## Mineral associations This mineral coexists with other rare arsenates and sulfates formed under similar conditions. The most important associated minerals include: johillerite, erythrosiderite, lammerite, hematite, tenorite, arcanite, langbeinite, aphthitalite, anhydrite, and sylvite. ## Localities The only confirmed locality for bradaczekite in the world is its type locality – the Yadovitaya fumarole on the second cinder cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption (1975-1976) in Kamchatka, Russia.

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. Specimens with clearly visible, well-formed, undamaged tabular crystals forming dense aggregates are most valued. The contrast of dark green crystals with the lighter host rock also enhances visual appeal. ## Popular localities The only source of bradaczekite specimens is its discovery site – Tolbachik volcano in Kamchatka. Material from this locality is extremely limited and primarily available through specialized dealers focusing on minerals from this region.

Care and storage

## Cleaning Due to the extreme rarity, small size, and fragility of the crystals, mechanical cleaning is not recommended. Specimens should be protected from dust by storing them in sealed containers. ## What to avoid Avoid contact with chemicals, especially acids, which can damage the mineral. The crystals are brittle and sensitive to shocks and ultrasound. They should be protected from moisture and sudden temperature changes. ## Storage Bradaczekite specimens should be stored under stable conditions, in specialized "micromount" boxes that protect them from mechanical damage, dust, and moisture. They should not be exposed to direct sunlight.

Sources

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