Fluorokinoshitalite

Chemical formula: BaMg₃Al₂Si₂O₁₀F₂

Fluorokinoshitalite is a rare mineral from the brittle mica group, being the fluorine analog of kinoshitalite, occurring as colorless, transparent flakes.

## Characteristics Fluorokinoshitalite is a mineral belonging to the brittle mica group. It forms small, hexagonal in outline, platy or scaly crystals, which can occur as rosette-like aggregates. It is colorless and transparent, which, combined with its platy form, gives it a specific appearance. As a member of the brittle mica group, it is more fragile than typical micas. ## Physical properties This mineral is characterized by perfect cleavage in one plane, typical of micas, which allows for easy separation of thin flakes. Its density is approximately 3.235 g/cm³. The luster is vitreous. The Mohs hardness is not precisely determined, but for minerals in this group, it typically ranges from 2.5-3. ## Colors and varieties Fluorokinoshitalite is usually colorless. No colored or commercial varieties have been distinguished for it. ## History and name The mineral's name refers to its chemical composition – it is an analog of kinoshitalite with dominant fluorine in place of the hydroxyl (OH) group. It was first described by M. Shigezawa and S. Iwao in 1982. The type locality (locus typicus) is the East Mine in the Bayan Obo deposit in China. ## Applications Fluorokinoshitalite has no industrial application. Its significance is purely scientific and collectible, as a rare representative of the brittle mica group.

Properties

Mohs hardness
2.5-3
Luster
Vitreous
Streak
White
Density
3.235
Cleavage
on {001}.
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Fluorokinoshitalite is identified by its platy or scaly form, hexagonal crystal outline, perfect cleavage in one direction, and colorless, transparent nature. Its brittleness is a distinguishing feature from more elastic micas, such as muscovite. ## Distinguishing from similar minerals It can be confused with other colorless micas, such as muscovite or phlogopite. It differs from them by the greater brittleness of its flakes. Similar kinoshitalite is its hydroxyl analog, and distinguishing these two minerals without advanced chemical analyses (e.g., EDS) is practically impossible. It differs from talc by its greater hardness and luster. ## Crystal forms Crystals have the form of thin, pseudohexagonal tablets and flakes. They often form rosette-like, scaly, or platy aggregates.

Geological environment

## Genesis It is a mineral of metamorphic origin. It forms in carbonate rocks (carbonatites) or skarns that have undergone contact metamorphism under conditions of high temperature and low pressure, in a barium and fluorine-rich environment. ## Mineral associations At the type locality (Bayan Obo), it co-occurs with minerals such as calcite, dolomite, phlogopite, diopside, magnetite, apatite, baryte, and huanghoite-(Ce). ## Localities The most important and best-documented occurrence of fluorokinoshitalite is its type locality – the Bayan Obo iron and rare earth element deposit in the Inner Mongolia Autonomous Region, China.

Rarity

Very rare

For collectors

## Quality criteria For collectors, the most valuable specimens are those with well-formed, sharp crystals with a pseudohexagonal outline, forming aesthetic, rosette-like aggregates. Transparency and absence of mechanical damage are important. Due to its rarity, even small but well-defined crystals are prized. A contrasting rock matrix enhances the specimen's appeal. ## Popular localities The only source of collectible specimens is the Bayan Obo deposit in China. Specimens from this locality are the standard for this mineral.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Compressed air can be used from a safe distance. Due to its perfect cleavage, avoid washing in water, especially under pressure, as this can lead to delamination and destruction of the crystals. ## What to avoid Avoid contact with chemicals, especially acids. The mineral is brittle and susceptible to mechanical damage, such as impacts, scratches, or bending of flakes. It should not be heated or subjected to ultrasound. ## Storage Fluorokinoshitalite specimens are best stored in closed display boxes that protect against dust and mechanical damage. Avoid placing other, heavier minerals on top of them.

External references

Sources

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