Zirklerite

Chemical formula: (Fe₂+,Mg)₉Al₄Cl₁₈(OH)₁₂·₁₄H₂O

Zirkleryte is a very rare, hydrated iron, magnesium, and aluminum chloride, forming fibrous or earthy aggregates of a yellowish-white color.

## Characteristics Zirkleryte is a halide mineral, chemically classified as a hydrated iron, magnesium, and aluminum chloride. It occurs extremely rarely, usually in the form of very fine, fibrous aggregates or earthy masses. Its brittle and delicate nature means that well-formed crystals are not known. It typically forms coatings and veins within salt rocks. ## Physical Properties This mineral is characterized by a very low hardness, approximately 1 on the Mohs scale, which means it is extremely soft and can be scratched with a fingernail. It has a silky luster, and its transparency ranges from translucent to opaque. It is lightweight, with a density of about 1.96 g/cm³. ## Colors and Varieties Zirkleryte occurs in shades from yellowish-white to waxy-yellow. No color or commercial varieties have been distinguished. ## History and Name The mineral's name honors Ferdinand Zirkel (1838-1912), a German geologist and petrologist, professor of mineralogy at the University of Leipzig. It was first described in 1928 based on material found in Germany.

Properties

Mohs hardness: 1
Luster: Silky
Streak: White
Density: 1.96
Cleavage: None
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Trigonal

Diagnostic features

## Identification Zirkleryte can be identified by its exceptional softness (hardness 1), silky luster, fibrous or earthy habit, and yellowish-white color. Its occurrence in paragenesis with salt rocks is also characteristic. ## Distinguishing from Similar Minerals It can be confused with other secondary salt minerals of similar appearance, such as carnallite or bischofite. Differentiation usually requires advanced analytical methods, such as X-ray diffraction (XRD), due to its rarity and lack of distinct macroscopic features. ## Crystal Forms Zirkleryte forms fibrous aggregates, radial aggregates, or earthy masses. It has not been observed in the form of well-developed, single crystals.

Geological environment

## Genesis It is a secondary mineral, formed by the alteration of other minerals within rock salt deposits (evaporites). It forms in a chloride-rich environment under low-temperature conditions. ## Mineral Associations It most commonly co-occurs with minerals such as halite, sylvite, carnallite, bischofite, kieserite, and rinneite. ## Localities The most important and classic localities for this mineral are in Germany, within Zechstein salt domes, e.g., in potash salt mines in Lower Saxony (Riedel mine in Hänigsen) and Saxony-Anhalt (Leopoldshall mine in Staßfurt).

Rarity

Very rare

For collectors

## Quality Criteria The quality of a zirkleryte specimen is primarily assessed based on the abundance of material and its purity. Since this mineral does not form aesthetic crystals, the most valued specimens are rich fibrous aggregates or coatings on a rock matrix, clearly contrasting with associated minerals (e.g., halite). Accurate locality documentation is also important. ## Popular Localities German salt mines in the Hanover and Staßfurt regions are the source of the best-known specimens and represent classic localities for this species.

Care and storage

## Cleaning Due to its extreme softness and potential water solubility, zirkleryte should not be wet cleaned. The safest method is to gently remove dust with a soft brush or a stream of compressed air from a distance. ## What to Avoid Contact with water, chemicals, acids, and detergents must be strictly avoided. The mineral is hygroscopic and can absorb moisture from the air, leading to its degradation. It should be protected from high temperatures and direct sunlight. ## Storage Zirkleryte specimens must be stored in dry conditions, preferably in an airtight container (e.g., a "membrane box") with a desiccant (silica gel). It should be kept away from other minerals to avoid mechanical damage.

Sources

IMA Mineral List (CNMNC)