D'ansite

Chemical formula: Na₂₁Mg(S⁶⁺O₄)₁₀Cl₃

D'Ansite is a rare, water-soluble sulfate and chloride of sodium and magnesium, forming small, colorless or yellowish crystals in rock salt deposits.

## Characteristics D'Ansite is a complex sulfate and chloride of sodium and magnesium, belonging to the d'ansite group. This mineral typically forms small, isometric crystals, often in the shape of tetrahedra or cubes, which may be modified by other forms. It occurs as granular aggregates or single, well-formed crystals embedded in halite. It is a brittle and hygroscopic mineral. ## Physical Properties D'Ansite crystals are relatively soft, with a Mohs hardness of 2.5-3. They have a vitreous luster and are translucent. The mineral's density is approximately 2.63 g/cm³. Due to its water solubility, specimens are sensitive to moisture. ## Colors and Varieties D'Ansite is most often colorless, but can be yellow or pale brown. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral was named after Jean D'Ans (1881-1969), a German chemist and mineralogist, who first synthesized its equivalent in the laboratory in 1907. It was described as a mineral in 1957 by Fritz Löffler and Walter E. H. B. H. F. Feitknecht based on specimens from the salt mine in the Hall Valley in Tyrol, Austria. ## Uses D'Ansite has no industrial applications. It is solely a mineral of scientific and collector's interest.

Properties

Mohs hardness
2.5-3
Luster
Vitreous
Streak
White
Density
2.63
Cleavage
None
Fracture
Uneven
Transparency
Translucent
Crystal system
Isometric

Diagnostic features

## Identification The key diagnostic features of d'ansite are its occurrence in evaporitic rock salt deposits, its regular (isometric) crystal habit, and its water solubility. It reacts to moisture, becoming sticky to the touch. It has a white streak and a vitreous luster. ## Distinguishing from Similar Minerals D'ansite can be confused with other evaporites, mainly halite (NaCl) and sylvite (KCl). Halite has perfect cubic cleavage and a salty taste, whereas d'ansite is brittle and does not exhibit such distinct cleavage. It is distinguished from other rare sulfates by its crystal form and specific environment of occurrence. ## Crystal Forms D'ansite crystallizes in the isometric system, most often forming tetrahedral crystals, less commonly cubes. Crystals are usually small, not exceeding a few millimeters in size, often embedded in the salt mass.

Geological environment

## Genesis D'ansite is an evaporitic mineral. It forms in the final stages of crystallization of marine brines, under conditions of high concentrations of sulfates and chlorides of sodium and magnesium. It is a typical component of some rock salt deposits. ## Mineral Associations This mineral co-occurs with other salts, such as halite, sylvite, anhydrite, gypsum, polyhalite, kainite, blödite, and vanthoffite. ## Localities The most important and classic locality (type locality) for d'ansite is the salt mine in the Hall Valley (Halltal) near Absam in Tyrol, Austria. It is also known from other salt deposits, including in Germany (e.g., near Hanover) and Russia.

Rarity

Rare

For collectors

## Quality Criteria The most prized d'ansite specimens are those with well-formed, sharp, and transparent crystals, clearly contrasting with the matrix, which is most often halite. Due to the rarity of the mineral, even small but well-formed crystals are sought after by collectors specializing in systematic minerals or those from specific localities. Crystal size rarely exceeds a few millimeters, so size is not the primary criterion. ## Popular Localities By far the most desirable specimens come from the type locality in the Hall Valley, Austria. These are considered classic and have the greatest historical and collector value.

Care and storage

## Cleaning Cleaning d'ansite is highly problematic due to its water solubility. Contact with water and other liquids must be avoided. Only gentle, mechanical dust removal using a soft brush or compressed air from a safe distance is permissible. ## What to Avoid Contact with water, water vapor, and high humidity must be strictly avoided, as these can quickly damage or completely dissolve the specimen. The mineral should be protected from chemicals, acids, and detergents. It should not be heated. ## Storage D'ansite specimens must be stored in dry conditions. It is recommended to keep them in tightly sealed containers (e.g., "perky box" type) with a desiccant (e.g., silica gel). Display should be in closed, airtight display cases.

External references

Sources

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