Drobecite

Chemical formula: Cd<sup>2+</sup>S<sup>6+</sup>O<sub>4</sub>·4H<sub>2</sub>O

Droběcite is a hydrated cadmium sulfate, forming colorless, acicular crystals, and is a rare secondary mineral.

## Characteristics Droběcite is a hydrated cadmium sulfate. It occurs as very small, acicular or capillary crystals, which usually form crusts, coatings, or fluffy aggregates on rock surfaces. Individual crystals are colorless and transparent, and their small size makes them appear white with a silky luster in aggregates. ## Physical Properties Droběcite crystals are flexible and can be bent. The mineral's hardness is low, estimated at about 2.5 on the Mohs scale. Its density is approximately 3.03 g/cm³. The luster is vitreous on individual crystals, becoming silky in aggregates. ## Colors and Varieties The mineral is colorless; in aggregates, it appears white. No varieties have been distinguished. ## History and Name Droběcite was discovered in the Schlemā-Alberoda uranium mine in the Ore Mountains (Saxony, Germany). It was approved as a new mineral in 2002. Its name honors the Czech mineral collector, Jaroslav Drobeček (1947-2001), who first found this mineral. ## Applications Due to its extreme rarity and small crystal size, droběcite has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized collectors of rare minerals.

Properties

Mohs hardness
2.5
Luster
Vitreous, Silky
Streak
White
Density
3.03
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Droběcite is difficult to identify visually without specialized equipment. Characteristic features include fluffy, acicular or capillary aggregates of white color and silky luster, occurring in paragenesis with other secondary sulfates on sulfide-rich host rocks. ## Distinguishing from Similar Minerals It can be confused with many other secondary sulfates of similar appearance, such as gypsum, melanterite, epsomite, or goslarite. Reliable distinction is almost exclusively possible through chemical analysis (EDS) or X-ray diffraction (XRD) to confirm the presence of cadmium and the crystal structure. ## Crystal Forms It forms very fine, elongated crystals with an acicular or capillary habit. These crystals combine into tangled, fluffy aggregates, crusts, and coatings.

Geological environment

## Genesis Droběcite is a secondary mineral. It forms in the oxidation (weathering) zones of ore deposits, as a result of the reaction of percolating waters with cadmium-bearing minerals, such as greenockite (CdS) or cadmium-rich sphalerite. It is a product of post-mining activity in old mines. ## Mineral Associations It co-occurs with other secondary minerals, mainly sulfates. In its type locality (Schlemā-Alberoda), it was found in association with gypsum, gunningite, bianchite, melanterite, and goslarite. ## Localities It is an extremely rare mineral, known from only a few localities worldwide. Besides the type locality in Schlemā-Alberoda, Germany, its occurrence has also been confirmed in the Christiana Levin mine in Essen (Germany) and in mines near Kladno in the Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria The collector's appeal of droběcite primarily depends on the richness and aesthetics of the aggregates on the rock matrix. Specimens with visible, abundant crusts of white, acicular crystals, forming a good contrast with the substrate, are most valued. Due to the microscopic size of the crystals, the purity and form of individual needles are not a key criterion – the overall appearance of the aggregate is what matters. ## Popular Localities The most known and valued specimens come from the type locality, the Schlemā-Alberoda mine in the German Ore Mountains. This is a classic locality for this mineral.

Care and storage

## Cleaning Droběcite specimens are extremely delicate and sensitive to water. They should not be wet cleaned. Only very careful dust removal with a soft brush or a stream of compressed air from a distance is permissible. ## What to Avoid Contact with water, which can dissolve the mineral, must be absolutely avoided. It should be protected from all chemicals, high temperatures, and changes in humidity. The crystals are very brittle and fragile. ## Storage Droběcite requires storage in stable conditions. It is best kept in a sealed, closed "micromount" box, which will protect it from mechanical damage, dust, and fluctuations in air humidity.

Sources

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