Fluoro-oxy-ferri-magnesiokatophorite

Chemical formula: Na₂Ca(Mg₄Fe₃+)(Si₇Al)O₂₂(F,O,OH)₂

An extremely rare sodium-calcium amphibole, a fluoro-oxy analog of ferri-magnesio-katophorite, of purely scientific significance.

## Characteristics Fluoro-oxy-ferri-magnesio-katophorite is a very rare mineral from the sodium-calcium amphibole group. It is a fluoro-oxy, magnesium- and iron (Fe³⁺)-dominant analog of katophorite. It occurs as very fine, prismatic crystals up to 100 micrometers long, forming aggregates within the host rock. Due to the microscopic size of the crystals, its visual characteristics cannot be assessed with the naked eye. ## Physical Properties Crystals exhibit a vitreous luster. The mineral is brittle. Hardness and density have not been precisely measured due to the small amount of available material, but are estimated to be typical for amphiboles. ## Colors and Varieties The observed crystals are dark brown. No varieties of this mineral are distinguished. ## History and Name The mineral's name reflects its chemical composition: it indicates the dominance of fluorine (Fluoro-), oxygen (oxy-), trivalent iron (ferri-), and magnesium (magnesio-), and its structural relationship to katophorite. It was approved by the International Mineralogical Association (IMA) in 2023 (IMA2023-013). It was described by G.O. Liferovich and collaborators based on material from the type locality. ## Uses The mineral has no commercial or industrial applications. Its significance is purely scientific and as a collector's item, as a unique member of the amphibole group.

Properties

Mohs hardness: 5-6
Luster: Vitreous
Streak: Pale brown
Density: 3.2-3.3
Cleavage: Perfect on {110}
Fracture: Uneven
Transparency: Translucent to opaque in larger fragments
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of this mineral is impossible without advanced analytical techniques. It requires chemical analysis (e.g., electron microprobe - EDS/WDS) to determine composition and diffraction methods (e.g., X-ray diffraction - XRD) to confirm the crystal structure. The dark brown color and prismatic appearance on a micro scale are indicative features, but non-specific. ## Distinguishing from Similar Minerals It can be confused with many other dark amphiboles (e.g., hornblende, arfvedsonite, other katophorites) or pyroxenes, with which it co-occurs. Differentiation relies solely on precise chemical analysis, which must demonstrate the specific combination of dominant magnesium, Fe³⁺ iron, fluorine, and oxygen in the appropriate structural positions. ## Crystal Forms The mineral forms elongated, prismatic crystals, occurring as inclusions in other minerals or forming small, radial aggregates.

Geological environment

## Genesis Fluoro-oxy-ferri-magnesio-katophorite forms under conditions of high-grade contact metamorphism (fenitized metamorphic facies). It forms in fenites – rocks resulting from alkaline metasomatism, associated with intrusions of alkaline rocks and carbonatites. ## Mineral Associations The mineral co-occurs with aegirine, microcline, nepheline, titanite, apatite, pyrochlore, zircon, and other amphiboles and pyroxenes. ## Localities The only confirmed occurrence worldwide (type locality) is the Afrikanda massif on the Kola Peninsula in the Murmansk Oblast, Russia. This is a classic locality for many rare alkaline minerals.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, its collector's value is not assessed based on typical criteria such as size or luster. The most valuable specimens are those where the mineral has been unequivocally identified analytically. The abundance of crystals on the rock matrix and the presence of well-formed, though still microscopic, crystal forms enhance its value. Association with other rare minerals from this locality is also desirable. ## Popular Localities The only source of specimens is the Afrikanda massif in Russia. Material from this locality is extremely difficult to acquire.

Care and storage

## Cleaning Due to its extreme rarity and microscopic nature, specimens of this mineral (usually as a fragment of the host rock) should not be subjected to any invasive cleaning methods. Any contaminants should be removed exclusively with compressed air or, as a last resort, a very soft brush. ## What to Avoid Avoid contact with all chemicals, acids, and detergents. Do not subject it to ultrasonic cleaning. Protect from extreme temperatures and humidity. ## Storage Specimens should be stored under stable conditions, in a sealed "micromount" box, to protect them from dust and mechanical damage. Avoid direct exposure to sunlight, although there is no evidence of fading.

Sources

IMA Mineral List (CNMNC)