Ferri-fluoro-leakeite
Chemical formula: NaNa₂(Mg₂Fe³⁺₂Li)Si₈O₂₂F₂
A black or yellow, rare silicate from the amphibole group, discovered in Kazakhstan, distinguished by its complex chemical composition with lithium and fluorine.
Properties
- Mohs hardness
- 6-0
- Luster
- Vitreous
- Streak
- Very pale grey to white
- Density
- 3.245
- Cleavage
- Perfect {110}, intersecting at ~56º, characteristic of monoclinic amphiboles.
- Fracture
- Splintery
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identifying ferri-fluoro-leakeite in the field is practically impossible without advanced analysis. In a collection, it can be tentatively identified based on its characteristic color (black or mustard-yellow), aggregate form (fibrous, columnar), and most importantly, the confirmed origin locality – the Verkhnee Espe massif. ## Distinguishing from Similar Minerals This mineral can be confused with many other black or yellowish-brown amphiboles, such as arfvedsonite, riebeckite, or other minerals from the leakeite group. Definitive differentiation requires specialized studies, such as chemical analysis (EDS/WDS) to confirm the presence and proportions of sodium, magnesium, iron, lithium, and fluorine. ## Crystal Forms Ferri-fluoro-leakeite most commonly occurs as fibrous, acicular, or prismatic (columnar) aggregates. Well-formed, single crystals are extremely rare.
Geological environment
## Genesis Ferri-fluoro-leakeite is a mineral of metamorphic origin. It forms under specific conditions within metasomatically altered alkaline rocks, such as syenites. Its formation is associated with the presence of high concentrations of sodium, lithium, and fluorine. ## Mineral Associations This mineral coexists with other rare minerals typical of its formation environment. At the type locality (Verkhnee Espe), it has been found in association with quartz, microcline, aegirine, riebeckite, narsarsukite, and other rare silicates and fluorides. ## Localities The only confirmed and described occurrence of ferri-fluoro-leakeite in the world is its type locality – the Verkhnee Espe massif in the Tarbagatai Mountains, Abai Region, eastern Kazakhstan.
Rarity
Very rare
For collectors
## Quality Criteria The collector's appeal of ferri-fluoro-leakeite specimens primarily depends on the richness and visibility of aggregates on the rock matrix. Most valued are specimens with distinct, dense aggregates of intense, mustard-yellow color, contrasting with the surrounding rock. The size of the specimen and the presence of associated minerals also increase its value. ## Popular Localities The only source of specimens of this mineral is its type locality in Kazakhstan. All specimens available on the collector's market originate from this single location.
Care and storage
## Cleaning Specimens should only be cleaned mechanically, using a soft brush to remove dust. Due to the fibrous or acicular nature of the aggregates, extreme caution should be exercised to avoid damaging delicate crystals. The use of water is not recommended without certainty regarding the stability of the specimen and the accompanying rock. ## What to Avoid Avoid contact with all chemicals, especially acids, which can react with the mineral's components. Ultrasonic cleaners should also be avoided, as they can destroy delicate aggregates. Do not expose the specimen to sudden temperature changes. ## Storage Ferri-fluoro-leakeite specimens should be stored in stable conditions, away from dust and direct sunlight. It is best to place them in a closed display box to minimize the risk of mechanical damage.