Kuzelite
Chemical formula: Ca<sub>4</sub>Al<sub>2</sub>(OH)<sub>12</sub>(S<sup>6+</sup>O<sub>4</sub>)·6H<sub>2</sub>O
Kuzelite is a rare mineral from the ettringite group, forming colorless or white, hexagonal tabular crystals with perfect cleavage.
Properties
- Mohs hardness
- 2.5
- Luster
- Vitreous, Pearly on cleavages
- Streak
- White
- Density
- 2.01
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Transparent to Translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification The most important diagnostic feature of kuzelite is its habit in the form of hexagonal, tabular crystals. Other important features include low hardness, perfect cleavage in one direction with a pearly luster on cleavage planes, and occurrence in a specific geological environment. ## Distinguishing from Similar Minerals Kuzelite is sometimes confused with other white tabular minerals, such as brucite or gibbsite. Distinguishing it based on appearance is difficult and often requires chemical or X-ray diffraction (XRD) analysis. Identification of associated minerals, typical for its paragenesis (e.g., ettringite, afwillite), is helpful. ## Crystal Forms Kuzelite crystals have a tabular, hexagonal habit. They are usually small, with a diameter not exceeding a few millimeters. They often grow together into rosette-like or fan-shaped aggregates, and also form thin crusts on rocks.
Geological environment
## Genesis Kuzelite is a secondary mineral, forming under low-temperature alteration conditions. It most commonly forms in carbonate rock xenoliths (limestones) contact-metamorphosed by basaltic magma. It is also a known phase formed during portland cement hydration. ## Mineral Associations This mineral co-occurs with other rare contact limestone minerals, such as ettringite, afwillite, tobermorite, hydrocalumite, jennite, as well as calcite and minerals from the apophyllite group. ## Localities The most important kuzelite localities in the world are few. They primarily include the type locality - the Zeilberg quarry in Bavaria and the Bellerberg volcanic complex in the Eifel mountains in Germany. It is also known from the Hatrurim Formation in Israel, as well as from isolated occurrences in Japan and Russia.
Rarity
Very rare
For collectors
## Quality Criteria The collector's value of kuzelite depends on the perfection and size of its hexagonal crystals. The most prized are well-formed, sharp, transparent plates, especially those forming aesthetic, rosette-like aggregates. Specimens where kuzelite contrasts with colorful host rock or co-occurs with other rare minerals are also highly valued. ## Popular Localities The German localities: Zeilberg quarry in Bavaria and the Bellerberg area in Eifel, are considered classic and provide the best specimens. Specimens from these locations are most sought after by collectors specializing in microminerals and rare minerals.
Care and storage
## Cleaning Kuzelite specimens are extremely delicate and soft. To remove dust, use only a soft brush or carefully blow off dust with an air blower from a photographic bulb. Avoid any contact with water and other liquids. ## What to Avoid The mineral is sensitive to water, which can lead to its damage or disintegration. Contact with acids and other chemicals should be strictly avoided. Due to its low hardness and perfect cleavage, it is very susceptible to mechanical damage, including scratches and fractures. ## Storage It is recommended to store specimens in closed, padded boxes (e.g., "micromount" type) to protect them from dust, moisture, and physical damage. Stable environmental conditions should be ensured, away from sources of vibration and sudden temperature changes.