Scandio-fluoro-eckermannite

Chemical formula: NaNa₂(Mg₄Sc)(Si₈O₂₂)F₂

Scandio-fluoro-eckermannite is a very rare sodium amphibole, distinguished by the presence of scandium and fluorine in its structure.

## Characteristics Scandio-fluoro-eckermannite is an extremely rare mineral from the sodium amphibole group. It occurs as small, columnar crystals, usually not exceeding 1 mm in length, forming radial aggregates. Its color ranges from dark green to almost black, and due to the small size of the crystals, detailed visual features are difficult to observe without magnification. ## Physical Properties This mineral is characterized by a vitreous luster. It is translucent in thin fragments, and appears opaque in mass. Its Mohs hardness is about 5-6, which is typical for amphiboles. Crystals exhibit perfect cleavage in two directions. ## Colors and Varieties The observed color is dark green, transitioning to black. No varieties of this mineral are known. ## History and Name The mineral's name directly refers to its chemical composition – indicating the dominance of scandium (Scandio) and fluorine (fluoro), and its structural relationship with eckermannite, another mineral from the amphibole group. It was formally described and approved by the International Mineralogical Association (IMA) under number 2019-093. The discovery was made in the Gjerdingselva alkaline complex in Norway. ## Uses Due to its extreme rarity and microscopic size, scandio-fluoro-eckermannite has no commercial or industrial applications. Its significance is purely scientific and as a collector's item, as a unique representative of scandium-rich amphiboles.

Properties

Mohs hardness: 5-6
Luster: Vitreous
Streak: Pale grayish green
Density: 3.23
Cleavage: Perfect on {110}
Fracture: Uneven
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of this mineral is impossible without advanced analytical techniques, such as electron spectroscopy (EDS/WDS) to confirm its unique chemical composition, especially the high content of scandium and fluorine. Visually, in the form of dark green, radial acicular aggregates, it may resemble other amphiboles. ## Distinguishing from Similar Minerals It can be confused with other dark amphiboles, such as arfvedsonite, riebeckite, or other varieties of eckermannite. The key distinguishing feature is the chemical composition, which requires specialized analysis. Its occurrence in a specific geological environment (nepheline syenite) is an important clue. ## Crystal Forms It forms prismatic, columnar to acicular crystals, most often occurring as radial or tangled aggregates.

Geological environment

## Genesis Scandio-fluoro-eckermannite forms in the late stage of crystallization within pegmatites associated with nepheline syenites. It is an igneous mineral, crystallizing from residual fluids enriched in rare elements (like scandium) and volatile elements (like fluorine). ## Mineral Associations This mineral occurs in association with other minerals typical of alkaline pegmatites, such as microcline, nepheline, aegirine, astrophyllite, zircon, mosandrite-(Ce), and other rare minerals, including vittite-(Ce). ## Localities The only confirmed locality (type locality) of this mineral in the world is the Gjerdingselva alkaline complex, in Lunner municipality, Viken county, Norway.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a scandio-fluoro-eckermannite specimen is primarily assessed based on the richness and visibility of the aggregates on the rock matrix. The most desirable specimens are those with clearly formed, radial clusters of dark green crystals, contrasting with the lighter host rock. Due to its microscopic nature, the size of individual crystals is not a key criterion; the overall aesthetics of the aggregate are what matters. ## Popular Localities The only source of specimens is the type locality in Norway – the Gjerdingselva complex. All specimens available on the collector's market originate from this single location.

Care and storage

## Cleaning Due to the microscopic size of the crystals and their occurrence on the rock matrix, mechanical cleaning is not recommended. If dust removal is necessary, compressed air from a safe distance or a very soft brush can be used. ## What to Avoid Avoid contact with strong acids and chemicals that could damage both the mineral and the host rock. The specimen should not be subjected to ultrasound. Due to the presence of fluorine, heating should be avoided. ## Storage Specimens should be stored in stable conditions, in enclosed "micromount" boxes, to protect them from dust and mechanical damage. Direct exposure to sunlight should be avoided, although there is no evidence of its particular sensitivity.

Sources

IMA Mineral List (CNMNC)