Kreiterite
Chemical formula: CsLi<sub>2</sub>Fe<sup>3+</sup>Si<sub>4</sub>O<sub>10</sub>F<sub>2</sub>
Kreiterite is an extremely rare cesium, lithium, and iron silicate with microscopic, platy crystals, discovered in the Tanco pegmatite in Canada.
Description
## Characteristics Kreiterite is a mineral from the phyllosilicate group, closely related to micas. It forms very small, elongated, lath-like or platy crystals, which usually occur as aggregates. Individual crystals rarely exceed 150 micrometers in length. Due to the microscopic size of the crystals, its macroscopic features are difficult to observe without specialized equipment. ## Physical Properties The mineral is characterized by a vitreous luster, and on cleavage surfaces, a pearly luster. It is opaque, becoming translucent only in very thin fragments. Its density, calculated based on chemical composition and unit cell parameters, is 3.23 g/cm³. Hardness has not been determined due to the too small size of the crystals. ## Colors and Varieties Kreiterite occurs in a uniform, dark brown to black color. No color or commercial varieties have been distinguished. ## History and Name The mineral's name honors Dr. Thomas Kreiter (born 1980), a geologist working at the Tanco mine, where the mineral was discovered. Kreiterite was officially approved by the International Mineralogical Association (IMA) in 2021 under number IMA2021-020. Its full scientific description was published in 2022 in the "Mineralogical Magazine" by Frank C. Hawthorne and his collaborators. ## Applications As a mineral of microscopic size and extreme rarity, kreiterite has no industrial application. It is solely an object of scientific research and a valuable acquisition for specialized collectors of systematic minerals and microminerals.
Diagnostic features
## Identification Identification of kreiterite is impossible based on visual features alone and requires advanced analytical techniques, such as chemical analysis (EDS/WDS) and X-ray diffraction (XRD). A clue may be its occurrence in a specific geological environment – in zones rich in pollucite within LCT-type pegmatites, in association with other rare minerals. ## Differentiation from Similar Minerals Kreiterite can be confused with other dark platy minerals, such as zinnwaldite or biotite, which may occur in similar parageneses. The key distinguishing feature of kreiterite is its unique chemical composition, especially its high cesium content, which cannot be determined without appropriate research equipment. ## Crystal Forms Kreiterite forms microscopic, lath-like or platy crystals with a lamellar habit, resembling micas. These crystals combine into small, often radial or disordered aggregates on the surface of other minerals.
Geological environment
## Genesis Kreiterite forms under unique geochemical conditions, characteristic of highly differentiated and fractionated LCT-type (lithium-cesium-tantalum) granitic pegmatites. Its formation is associated with late stages of crystallization, in zones with extreme concentration of rare elements, especially cesium. ## Mineral Associations This mineral occurs in direct proximity to quartz, albite, montebrasite, and zinnwaldite. Its presence is closely linked to zones rich in pollucite – the main cesium ore mineral. ## Localities The only confirmed locality of kreiterite in the world is its type locality – the Tanco mine, located on Bernic Lake in Manitoba, Canada. This is one of the world's most famous pegmatite deposits rich in rare elements.
Rarity
Extremely rare
Collector aspects
## Quality Criteria The quality of collector's specimens of kreiterite, being a micromineral, is assessed differently than in the case of large crystals. The most important criterion is the richness of the specimen – the quantity and density of kreiterite aggregates on the rock matrix. Specimens showing well-formed, though microscopic, crystalline forms are also valued. The aesthetics of the entire matrix and the presence of well-formed associated minerals are also of great importance. ## Popular Localities The only source of kreiterite specimens is the Tanco mine in Canada. Material from this locality is highly valued by collectors specializing in pegmatite minerals, systematic minerals, and microminerals.
Care and storage
## Cleaning Kreiterite specimens, typically microminerals on a rock matrix, should be cleaned with the utmost care. It is recommended to use a soft brush to remove dust or compressed air from a safe distance. Avoid contact with water and any chemical agents, unless absolutely necessary and preceded by a test on an inconspicuous fragment. ## What to Avoid The mineral is potentially sensitive to rapid temperature changes, strong acids, and bases. Ultrasonic cleaners should be avoided, as they can permanently damage delicate crystals and their aggregates. Protect from impacts and shocks. ## Storage Specimens should be stored under stable conditions, away from direct sunlight, dust, and moisture. The best solution is a sealed "micromount" box, which protects the delicate specimen from mechanical damage and contamination.