Zharchikhite
Chemical formula: Al(OH)<sub>2</sub>F
Zharchikhite is a rare aluminum fluoride, forming tiny, colorless to white crystals and aggregates, found in the oxidation zones of molybdenum-tungsten deposits.
Properties
- Mohs hardness
- 3
- Luster
- Vitreous, Pearly
- Streak
- White
- Density
- 2.45
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Identification of zharchikhite is primarily based on its characteristic habit – it forms very small, thin, tabular crystals, often grouped into rosettes or spherulites. Identification is confirmed by its occurrence locality (very few known locations) and associated minerals, such as fluorite or quartz. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other secondary minerals of similar appearance, such as gypsum (significantly softer) or muscovite (different crystal habit, more elastic lamellae). It differs from hydroxyapatite by its lower hardness and crystal habit. In practice, due to its rarity and small size, distinguishing it from other microcrystalline minerals without specialized equipment is almost impossible. ## Crystal Forms Crystals are tabular, hexagonal in outline, with a thickness of up to 0.01 mm and a diameter of up to 0.5 mm. They typically form rosette-like, spherulitic, or radial aggregates, as well as thin crusts and coatings.
Geological environment
## Genesis Zharchikhite is a secondary mineral, forming in the oxidation zones of ore deposits, particularly those rich in molybdenum, tungsten, and fluorine. It forms through low-temperature hydrothermal processes or weathering, in the presence of aluminum- and fluorine-rich solutions. ## Mineral Associations It most commonly co-occurs with fluorite, quartz, calcite, molybdenite, wolframite, scheelite, and other rare secondary minerals. ## Localities The most important and type locality is the Zharchikhinskoe molybdenum deposit in Buryatia, Russia. This is the only place where this mineral has been well-documented and occurs in larger quantities. Additionally, its presence has been noted in several other locations worldwide, but these occurrences are of purely scientific interest.
Rarity
Very rare
For collectors
## Quality Criteria The quality of zharchikhite specimens is primarily assessed based on the richness and aesthetics of the crystal aggregates on the rock matrix. The most valued specimens are those with well-formed, distinct rosettes or spherulites, contrasting with the substrate. Crystal size, although always small, is also important – the larger and better-formed they are, the more valuable the specimen. The absence of damage to the delicate aggregates is also crucial. ## Popular Localities The only source of collector specimens is its type locality – the Zharchikhinskoe deposit in Russia. Specimens from this location are considered the best in the world, and virtually all available on the market originate from there.
Care and storage
## Cleaning Zharchikhite specimens should be cleaned very carefully, exclusively using compressed air to remove dust. Due to its softness and perfect cleavage, contact with water and brushes should be avoided. ## What to Avoid All chemicals, especially acids, which can damage it, should be avoided. The mineral is soft and brittle, so it must be protected from impacts, scratching, and vibrations. Ultrasonic cleaning should not be performed. ## Storage Zharchikhite specimens, typically as microcrystals on a rock matrix, should be stored in sealed "micromount" boxes to protect them from dust and mechanical damage. Exposure to moisture should be avoided.