Calciolangbeinite

Chemical formula: K<sub>2</sub>Ca<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>3</sub>

Calciolangbeinite is a rare potassium calcium sulfate, forming colorless or white, isometric crystals with a vitreous luster.

## Characteristics Calciolangbeinite is a mineral from the sulfate group, chemically an anhydrous potassium calcium sulfate. It occurs as small, well-formed crystals with an isometric habit, most commonly tetrahedra, which may be modified by other forms. It is usually colorless to white and forms crystals with a vitreous luster. It is a member of the langbeinite group. ## Physical Properties This mineral is characterized by a Mohs hardness of approximately 2.5, making it relatively soft. Its density is about 2.83 g/cm³. Crystals are typically transparent to translucent and exhibit a vitreous luster. Luminescence has not been observed in it. ## Colors and Varieties Calciolangbeinite is usually colorless or white. No colored varieties or trade names are known. ## History and Name The mineral's name refers to its chemical composition – the presence of calcium (Latin: *calcius*) – and its structural and chemical similarity to langbeinite. It was first described by G.W. Volkov and I.I. Ostapenko in 1965 based on material found in a salt dome in Kazakhstan. ## Uses Due to its rarity and small crystal size, calciolangbeinite has no industrial applications. It is of scientific and collector interest only.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
White
Density
2.83
Cleavage
None
Fracture
Conchoidal
Transparency
Transparent to translucent
Crystal system
Cubic

Diagnostic features

## Identification Calciolangbeinite is identified by its isometric, tetrahedral crystals, vitreous luster, and occurrence in salt evaporites. A key diagnostic feature is its water solubility. It is a very soft mineral. ## Distinguishing from Similar Minerals It can be confused with other colorless salt minerals, such as halite or sylvite. It is distinguished from them by its crystal form (tetrahedra, not cubes like halite) and chemical composition. Langbeinite has very similar properties but does not contain calcium, which can only be determined by chemical analysis. ## Crystal Forms It forms isometric crystals, mainly in the form of tetrahedra, often with modifications of other forms. It occurs as single, grown crystals or in granular aggregates.

Geological environment

## Genesis It is an evaporitic mineral. It forms by precipitation from solutions rich in potassium, calcium, and sulfates in salt basins, under dry and hot climatic conditions. It forms in the final stages of marine brine evaporation. ## Mineral Associations It most commonly co-occurs with other salt minerals, such as halite, sylvite, polyhalite, kainite, gypsum, and anhydrite. ## Localities The most important occurrences of this mineral are in salt domes. It was discovered in the Inder region of Atyrau Oblast, Kazakhstan. It is also known from Zechstein salt deposits in Germany (e.g., near Hanover).

Rarity

Very rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp, and transparent crystals that are clearly visible on the rock matrix, most often on halite. Crystal size is a key factor, as they are usually very small. Contrast with the matrix mineral also enhances the specimen's attractiveness. ## Popular Localities Collector specimens primarily come from its type locality in Kazakhstan and from German potash salt mines.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. The mineral is water-soluble, so all contact with water and other liquids must be avoided. ## What to Avoid Contact with water, water vapor, and high humidity must be strictly avoided, as these can cause the specimen to dissolve and be destroyed. Chemicals, ultrasound, and rapid temperature changes should also be avoided. ## Storage Calciolangbeinite specimens must be stored in dry conditions, preferably in a sealed, airtight box with a desiccant (e.g., silica gel). They should be protected from dust and mechanical damage.

Sources

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