Fluorotaramite

Chemical formula: Na(NaCa)(Mg₃Al₂)(Si₆Al₂)O₂₂F₂

Fluorotaramite is a rare amphibole group mineral, the fluorine analogue of taramite, characterized by its black color and occurrence in ultramafic rocks.

## Characteristics Fluorotaramite is a rare, complex silicate from the amphibole supergroup, classified as the fluorine analogue of taramite. It typically forms small, columnar or prismatic crystals of black, or less commonly, very dark green color. It occurs as granular or radial aggregates embedded in rock. Due to its nature, it is a mineral primarily of interest to scientists and specialized collectors. ## Physical Properties This mineral exhibits a vitreous luster. It is opaque, and only in very thin fragments can it be slightly translucent. Its calculated density is approximately 3.36 g/cm³. The hardness has not been precisely measured, but for the amphibole group, it is typically 5-6 on the Mohs scale. ## Colors and Varieties Fluorotaramite is a mineral of uniform, black or greenish-black color. No color or commercial varieties are distinguished for it. ## History and Name The mineral's name refers to its chemical composition – the dominance of fluorine (fluoro) – and its structural relationship to taramite. It was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2006. The type locality, from which the first described specimens originated, is the Dugdug ultramafic massif in the Tuva Republic, Russia. ## Applications Fluorotaramite has no industrial application. It is solely an object of scientific research and is valued as a collector's mineral in systematic collections.

Properties

Mohs hardness: 5-6
Luster: Vitreous
Streak: Light grey
Density: 3.36
Cleavage: Perfect on {110}
Fracture: Uneven to splintery
Transparency: Opaque, translucent in thin splinters
Crystal system: Monoclinic

Diagnostic features

## Identification Macroscopic identification of fluorotaramite is impossible. Visually, it cannot be distinguished from other black amphiboles, such as hornblende, arfvedsonite, or taramite itself. The only reliable identification method is advanced chemical analysis, e.g., electron microprobe (EDS/WDS), which allows for the determination of the exact composition, including the high fluorine and sodium content crucial for this mineral. ## Distinguishing from Similar Minerals It differs from taramite by the dominance of fluorine over the hydroxyl (OH) group. From other black amphiboles (pargasite, hornblende), it is distinguished by specific proportions of calcium, sodium, iron, and aluminum in the crystal structure, which can only be determined by analytical methods. ## Crystal Forms Fluorotaramite forms elongated, prismatic crystals, which rarely occur in isolated form. It is most commonly found as granular, fibrous, or radial aggregates, embedded in the host rock.

Geological environment

## Genesis Fluorotaramite is a mineral of metamorphic and metasomatic origin. It forms under high-temperature conditions within ultramafic rocks, such as metasomatized gabbro-norites, where intense chemical exchange occurs with a fluorine-rich environment. ## Mineral Associations At the type locality in Russia, fluorotaramite co-occurs with minerals such as clinochlore, fluorapatite, ilmenite, pargasite, pyrrhotite, and spinel. ## Localities The most important and well-documented occurrence of fluorotaramite is the Dugdug ultramafic massif in Tuva (Russia). Its presence has also been reported in Finland in the Pargas area, known for the occurrence of many other amphiboles.

Rarity

Very rare

For collectors

## Quality Criteria As a mineral occurring mainly in the form of microscopic crystals, fluorotaramite is not evaluated according to typical criteria such as size or transparency. For collectors and scientific institutions, the most important aspects are the quality and certainty of specimen identification, confirmed by chemical analysis. The value is enhanced by abundant occurrence on the rock matrix and the presence of other rare minerals. ## Popular Localities The vast majority of reference and collector material comes from the type locality – the Dugdug massif in Russia.

Care and storage

## Cleaning Fluorotaramite specimens should only be cleaned mechanically, using a soft brush to remove dust. If necessary, distilled water can be used. Ultrasonic cleaners should be avoided, as they can damage the specimen along cleavage planes. ## What to Avoid The mineral is sensitive to strong acids. It should be protected from impacts and sudden temperature changes. It does not require special protection from light. ## Storage Store in stable conditions, in closed boxes or display cases, to protect it from dust and mechanical damage. It is recommended to separate it from harder minerals that could scratch it.

Sources

IMA Mineral List (CNMNC)