Cobaltlotharmeyerite

Chemical formula: CaCo²⁺₂(As⁵⁺O₄)₂·2H₂O

Cobaltlotharmeyerite is a rare calcium cobalt arsenate, forming characteristic reddish-purple crystals with a vitreous luster.

## Characteristics Cobaltlotharmeyerite is a hydrated calcium cobalt arsenate belonging to the tsumcorite group. This mineral forms very small, tabular or bladed crystals, rarely exceeding 0.5 mm in length. They typically occur as radial or rosette-like aggregates, as well as coatings and crusts on the host rock. Its intense, reddish-purple color makes it recognizable, despite the small size of the crystals. ## Physical Properties Cobaltlotharmeyerite crystals exhibit a vitreous luster. They are transparent to translucent. The Mohs hardness is approximately 4.5, and the density ranges between 4.33 and 4.49 g/cm³. This mineral is brittle and has an uneven fracture. ## Colors and Varieties This mineral occurs in a characteristic reddish-purple color. No varieties have been distinguished. ## History and Name Cobaltlotharmeyerite was first described in 1999 by Werner Krause, Heinz-Jürgen Bernhardt, Herbert Effenberger, and Hert Wefers. Its name refers to its chemical composition (cobalt dominance) and its relation to the structurally similar lotharmeyerite. The name was approved by the International Mineralogical Association (IMA). ## Uses Due to its rarity and small crystal size, cobaltlotharmeyerite has no industrial application. It is of scientific and collecting interest only.

Properties

Mohs hardness
4.5
Color
Light brown to reddish brown
Luster
Vitreous , Adamantine
Streak
Light brown
Density
0
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification The key diagnostic feature of cobaltlotharmeyerite is its intense reddish-purple color and characteristic radial aggregates composed of very small, tabular crystals. Co-occurrence with other cobalt and nickel arsenates in the oxidation zones of ore deposits is also an important clue. ## Distinguishing from Similar Minerals Cobaltlotharmeyerite can be confused with erythrite, which also forms red and purple coatings. However, erythrite usually has more acicular crystals and perfect cleavage in one direction, while cobaltlotharmeyerite forms aggregates of tabular crystals. Final distinction often requires advanced chemical analysis (EDS). ## Crystal Forms Crystals are very small, usually tabular or bladed, flattened parallel to {010}. They most often form radial or rosette-like aggregates, as well as spherulitic clusters and crusts.

Geological environment

## Genesis Cobaltlotharmeyerite is a secondary mineral, forming in the oxidation zones (gossans) of hydrothermal polymetallic deposits rich in arsenic, cobalt, and nickel. It forms as a result of the weathering of primary cobalt sulfides and arsenides. ## Mineral Associations This mineral co-occurs with other secondary arsenates, such as annabergite, erythrite, pharmacosiderite, scorodite, as well as with quartz, dolomite, and tennantite. ## Localities The most important and best-documented occurrences of this mineral are in Germany, in the Schneeberg area in Saxony (Pucher mine and Rappold mine), where it was discovered. It has also been found in the Aghbar mine in the Bou Azzer region of Morocco.

Rarity

Very rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with clearly formed, radial aggregates of intense, reddish-purple color, contrasting with a light host rock (most often quartz). Due to the microscopic size of the crystals, the quality and aesthetics of the entire aggregate, rather than individual crystals, are crucial. The richness of the surface coverage of the rock is also an important factor. ## Popular Localities Specimens from the type locality - Schneeberg in Germany - are the most classic and sought after by collectors specializing in mineral systematics or minerals from this region. Specimens from Bou Azzer in Morocco also appear on the collector's market.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to arsenic content, avoid inhaling dust and wash hands after contact with the mineral. The use of water is not recommended. ## What to Avoid Avoid contact with water, chemicals, especially acids, which can damage the mineral. Crystals are brittle and susceptible to mechanical damage, so ultrasonic cleaners should be avoided. Do not heat it. ## Storage Cobaltlotharmeyerite specimens should be stored in a dry place, in a closed display box, to protect them from dust and mechanical damage. Keep them away from direct sunlight, although its light sensitivity is not known.

External references

Sources

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