Fluor-rossmanite

Chemical formula: &#₉₇₂₃;(Al₂Li)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃F

Fluor-rossmanite is a very rare mineral from the tourmaline group, characterized by the dominance of fluorine at the W site and an almost complete absence of sodium.

## Characteristics Fluor-rossmanite is an extremely rare mineral belonging to the tourmaline group. It forms small, prismatic crystals, usually columnar in habit, terminated by a pyramid. Specimens are most often colorless or pale pink. Due to its extreme rarity and small crystal size, it is a mineral of primarily scientific and collector's interest. ## Physical Properties Crystals exhibit a hardness of approximately 7 on the Mohs scale. They have a vitreous luster and are transparent to translucent. The mineral's density is about 3.02 g/cm³. ## Colors and Varieties Observed colors are colorless and pale pink. No named varieties of this mineral have been distinguished. ## History and Name The name "Fluor-rossmanite" refers to its chemical composition – it is an analog of rossmanite with dominant fluorine (Fluor) at the anionic W site. The name was approved by the International Mineralogical Association (IMA) in 2016 (IMA2016-020). The mineral was discovered and described by a team of researchers, including Jan Cempírek, who is the first author of the publication describing this new mineral. ## Uses Fluor-rossmanite has no industrial applications. It is solely an object of scientific interest and constitutes a valuable and rare specimen in advanced systematic mineral and micromount collections.

Properties

Mohs hardness: 7-0
Color: light pink
Luster: Vitreous
Streak: white
Density: 3.07
Cleavage: None
Fracture: Conchoidal
Transparency: Transparent
Crystal system: Trigonal

Diagnostic features

## Identification Identification of fluor-rossmanite is impossible without advanced analytical techniques, such as spectroscopy and chemical analysis (e.g., electron microprobe). Visually, it is indistinguishable from other colorless or pale pink tourmalines, such as rossmanite, elbaite, or liddicoatite. The key diagnostic feature is the dominance of fluorine over hydroxyl (OH) groups at the W site in the chemical formula. ## Distinguishing from similar minerals It is distinguished from rossmanite by the dominance of fluorine over (OH) groups. From other tourmalines (elbaite, liddicoatite), it is distinguished by the almost complete absence of sodium and calcium at the X site. All these differences can only be determined by laboratory methods. ## Crystal forms It forms columnar, prismatic crystals with a triangular cross-section and rounded faces, typical of tourmalines. The crystals are terminated by a low-angle trigonal pyramid.

Geological environment

## Genesis Fluor-rossmanite forms in lithium- and fluorine-rich granitic pegmatites. It is a hydrothermal phase mineral, crystallizing in the late stages of pegmatite evolution, often within miarolitic cavities. ## Mineral associations This mineral co-occurs with other minerals typical of lithium pegmatites, such as quartz, albite (cleavelandite variety), elbaite, lepidolite, and microcline. ## Localities The only confirmed locality (type locality) of fluor-rossmanite in the world is the pegmatite in Řečice, near Nové Město na Moravě, in the Vysočina Region of the Czech Republic.

Rarity

Extremely rare

For collectors

## Quality criteria Due to its extreme rarity, every analytically confirmed specimen of fluor-rossmanite is extremely valuable. The most desirable are well-formed, transparent crystals, even small ones, clearly embedded in a rock matrix (e.g., on quartz or cleavelandite). Color contrast with the matrix enhances the specimen's attractiveness. ## Popular localities The only source of specimens is the type locality in the Czech Republic (Řečice). Material from this location is extremely difficult to acquire and appears on the collector's market sporadically.

Care and storage

## Cleaning Cleaning with compressed air only is recommended to remove dust. Due to the extreme rarity and potential fragility of small crystals, contact with water and any chemical agents should be avoided. ## What to avoid Avoid ultrasonic cleaners, sudden temperature changes, and contact with acids and other chemicals. Protect from impacts and scratches. ## Storage Fluor-rossmanite specimens, typically in the form of micromounts, should be stored in specialized boxes (so-called micromount boxes) that protect them from dust, moisture, and mechanical damage. Avoid exposure to direct sunlight.

External references

https://www.mindat.org/min-471056.html