Bearsite

Chemical formula: Be<sub>2</sub>As<sup>5+</sup>O<sub>4</sub>(OH)·4H<sub>2</sub>O

Bearsite is a very rare, hydrated beryllium arsenate, forming microscopic, colorless or white crystals and coatings.

## Characteristics Bearsite is a hydrated beryllium arsenate, occurring as very fine, microscopic crystals with a bladed or acicular habit. It typically forms small, radial aggregates, rosettes, or thin coatings and crusts on rock surfaces. Due to the size of its crystals, its visual features are difficult to observe without magnification. It is a secondary mineral, forming in the oxidation zones of ore deposits. ## Physical Properties Bearsite crystals exhibit a vitreous to pearly luster on cleavage surfaces. It is a transparent mineral. Its hardness and density have not been precisely determined due to the small size and rarity of samples. ## Colors and Varieties Bearsite is usually colorless or white. No varieties have been distinguished. ## History and Name The mineral's name refers to its chemical composition – it is an acronym derived from the elements that comprise it: **ber**yllium (**Be**) and **ars**enic (**As**). It was first described by I.G. Mineeva, K.V. Zubkova, N.I. Organova, D.A. Povarova, and V.I. Yakovenchuk in 2003 based on material from a granodiorite pegmatite in the Punnus-Yarvi Lake region of Karelia, Russia. It was approved by the International Mineralogical Association (IMA) in 2002 (IMA2002-044). ## Uses Bearsite has no industrial application. It is of purely scientific and collector's interest as a very rare mineral.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
White
Density
2.46
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identifying bearsite under amateur conditions is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS) to confirm the presence of beryllium and arsenic. Visually, it might be suspected as fine, white, radial aggregates in association with other arsenates in oxidation zones. ## Distinguishing from Similar Minerals It can be confused with many other secondary arsenate or sulfate minerals, such as pharmacolite, gypsum, or other rare beryllium arsenates (e.g., svornostite). Definitive differentiation is only possible through laboratory analysis. ## Crystal Forms Bearsite forms very small, bladed or acicular crystals, elongated along the [001] axis and flattened parallel to {010}. These crystals often combine into radial or stellate aggregates and rosettes.

Geological environment

## Genesis Bearsite is a secondary mineral that forms in the oxidation zones of ore deposits, particularly in pegmatites containing beryllium minerals (like beryl) and arsenic minerals (like arsenopyrite or löllingite). It forms as a result of the weathering of these primary minerals under low temperature and pressure conditions. ## Mineral Associations This mineral co-occurs with other arsenates and secondary minerals. In its type locality (Karelia, Russia), it was found in association with arsenopyrite, löllingite, beryl, kankite, scorodite, pharmacosiderite, gypsum, and quartz. In the Tsumeb mine (Namibia), it occurs with tennantite, galena, quartz, svornostite, and angelellite. ## Localities Bearsite is an extremely rare mineral, confirmed in only a few locations worldwide. The most important include: - Type locality: granodiorite pegmatite near Lake Punnus-Yarvi, Ladoga, Karelia, Russia. - Tsumeb Mine, Namibia – known for its exceptional and rare oxidation zone minerals. - Clara Mine in Rankach, Black Forest, Germany.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" type mineral, the collector's value of bearsite primarily depends on the quality and richness of the crystalline aggregates on the rock matrix. Specimens with clearly formed, radial clusters that are well visible under a microscope are most prized. Association with other rare minerals is also important, as it enhances the scientific and aesthetic value of the specimen. ## Popular Localities Due to its extreme rarity, every locality is valuable. Specimens from the Tsumeb mine in Namibia and the Clara mine in Germany are most sought after by specialized collectors of rare minerals, owing to the historical significance of these localities and the quality of the microminerals found there.

Care and storage

## Cleaning Bearsite specimens are extremely delicate and small. Any mechanical cleaning should be avoided. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Contact with water is not recommended due to its hydrated nature. ## What to Avoid Contact with water, acids, and other chemicals must be strictly avoided. The mineral is very soft and brittle, so it should be protected from shocks, impacts, and friction. It should not be heated or exposed to temperature changes. ## Storage Bearsite specimens should be stored under stable conditions, in closed, padded "micromount" boxes to protect them from mechanical damage, dust, and moisture. It is not suitable for display outside of a specialized container.

Sources

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