Dobšináite

Chemical formula: Ca₂Ca(As⁵⁺O₄)₂·2H₂O

Dobšináite is a hydrated calcium arsenate, forming colorless to white, platy crystals and radial aggregates, discovered in Dobšiná, Slovakia.

## Characteristics Dobšináite is a rare mineral from the arsenate group, chemically classified as a hydrated calcium arsenate. It occurs as very small, platy or acicular crystals, rarely exceeding 1 mm in length. These crystals often form radial or tangled aggregates, as well as thin coatings and crusts on rock surfaces. Due to the small size of the crystals, its visual features are difficult to observe without magnification. ## Physical Properties This mineral has a hardness ranging from 2.5-3 on the Mohs scale. It has a vitreous luster. It is transparent to translucent. The calculated density is approximately 3.19 g/cm³. ## Colors and Varieties Dobšináite is typically colorless to white. No color or commercial varieties have been distinguished. ## History and Name The mineral's name comes from its discovery locality – the historic mining town of Dobšiná (Slovak: Dobšiná) in Slovakia. It was officially approved as a new mineral by the International Mineralogical Association (IMA) in 2011 (IMA2011-025). It was described by a team of mineralogists: Jiří Sejkora, Jakub Plášil, Radek Škoda, and Milan Novák. ## Uses Dobšináite has no industrial applications. Its significance is purely scientific and as a collector's item, being a rare and recently discovered mineral species.

Properties

Mohs hardness
3
Color
White, pinkish, colourless
Luster
Vitreous
Streak
White
Density
3.395
Cleavage
On {010}
Fracture
Irregular/Uneven
Transparency
Transparent,Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of dobšináite is primarily based on its appearance – fine, platy crystals forming radial aggregates. The key is its occurrence locality (type locality) and co-occurrence with other arsenates. Final confirmation requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other secondary white arsenate minerals, such as pharmacolite, haidingerite, or picropharmakolite, which form similar aggregates. Pharmacolite often forms silky, fibrous aggregates. Haidingerite crystallizes in a different system and has perfect cleavage. A definitive distinction is almost exclusively possible through chemical and crystallographic analysis. ## Crystal Forms Crystals are strongly flattened, platy, elongated in one direction. They usually form fan-shaped or radial aggregates, as well as spherulitic groupings and thin crusts.

Geological environment

## Genesis Dobšináite is a secondary mineral, forming in the oxidation (weathering) zones of ore deposits containing arsenic minerals, especially arsenopyrite. It forms as a result of reactions between arsenic-rich solutions and calcium-rich minerals, such as calcite, under low temperature and pressure conditions. ## Mineral Associations At the type locality in Dobšiná, it co-occurs with calcite, arsenopyrite, pharmacolite, picropharmakolite, haidingerite, arsenolite, lavendulan, erythrite, and gypsum. ## Localities The only confirmed and described occurrence of dobšináite in the world is its type locality: the historic Zemberg iron and cobalt-nickel ore mine in Dobšiná, Rožňava district, Košice Region, Slovakia.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" mineral, the quality of a specimen is primarily determined by the abundance and development of crystals within the microscope's field of view. Specimens with well-defined, radial aggregates that clearly stand out from the host rock (matrix) are most valued. Association with other rare arsenates is also important, as it enhances the scientific and aesthetic value of the specimen. ## Popular Localities The only source of specimens is the type locality – the Zemberg mine in Dobšiná, Slovakia. Collector material from this location is very limited.

Care and storage

## Cleaning Due to the fragility and small size of the crystals, mechanical cleaning is highly risky. If necessary, compressed air can be carefully used to remove dust. Contact with water, especially deionized water, can be risky due to potential solubility. ## What to Avoid Contact with acids, which can rapidly decompose the mineral, must be absolutely avoided. It should be protected from high temperatures, which can lead to dehydration and structural damage. Avoid ultrasonics and any vibrations. ## Storage Dobšináite specimens should be stored under stable conditions, in sealed containers or display cases, to protect them from dust, mechanical damage, and sudden changes in humidity. It is best stored in its original "micromount" box.

External references

Sources

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