Åsgruvanite-(Ce)

Chemical formula: Ce<sup>3+</sup><sub>16</sub>Ca<sub>5</sub>Al(SiO<sub>4</sub>)<sub>6</sub>(As<sup>3+</sup>O<sub>3</sub>)<sub>8</sub>(CO<sub>3</sub>)<sub>2</sub>Cl<sub>4</sub>F<sub>3</sub>(OH)<sub>2</sub>

Åsgruvanite-(Ce) is an extremely rare cerium, calcium, and aluminum arsenosilicate, discovered in the Swedish Åsgruvan mine, distinguished by its complex chemical composition.

## Characteristics Åsgruvanite-(Ce) is a mineral with an exceptionally complex chemical composition, belonging to the group of silicates and arsenates. It occurs as very fine, hexagonal, prismatic crystals, rarely exceeding 0.1 mm in length. These crystals form radial aggregates or appear as single, isolated individuals embedded in the rock matrix. Due to the microscopic size of the crystals, its visual features are difficult to observe without specialized equipment. ## Physical Properties The crystals are too small to precisely determine their physical properties, such as hardness or density, by traditional methods. The density was calculated based on the chemical formula and unit cell parameters and is 4.88 g/cm³. The mineral exhibits a vitreous luster and is transparent to translucent. ## Colors and Varieties Åsgruvanite-(Ce) is pale yellow to yellowish-brown in color. No colored or commercial varieties have been observed. ## History and Name The mineral's name comes from its discovery locality – the Åsgruvan mine in the Bergslagen district, Sweden. The "-(Ce)" suffix in the name indicates the dominant rare earth element in its structure, which is cerium. It was officially recognized by the International Mineralogical Association (IMA) in 2023 under number IMA2023-034. The discovery was made by a team of mineralogists studying historical samples from this mine. ## Applications Due to its extreme rarity and microscopic size, Åsgruvanite-(Ce) has no industrial applications. It is solely an object of scientific and collecting interest for specialized micromineral collectors.

Properties

Luster
Vitreous
Streak
Light yellow
Density
4.88
Cleavage
Imperfect on {0001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Hexagonal

Diagnostic features

## Identification Identification of Åsgruvanite-(Ce) is possible only with advanced analytical techniques, such as energy-dispersive spectroscopy (EDS/EDX) combined with electron microscopy or X-ray diffraction (XRD). Visual identification in the field or even in a collection is impossible due to its microscopic size and similarity to other minerals from the same locality. ## Distinguishing from Similar Minerals This mineral can be confused with other rare silicates and arsenates occurring in the same paragenesis, such as dollaseite-(Ce) or other minerals from the allanite group. Definitive differentiation requires specialized chemical analysis to confirm its unique, complex composition. ## Crystal Forms It forms fine, hexagonal, prismatic crystals, often terminated by a pyramid. These crystals occur as single individuals or form small, radial aggregates.

Geological environment

## Genesis Åsgruvanite-(Ce) forms as a result of metamorphic processes in skarns. It occurs within dolomitic-calcitic marbles that have undergone contact metamorphism and metasomatism. Its formation is associated with the presence of rare earth elements, arsenic, chlorine, and fluorine in hydrothermal solutions. ## Mineral Associations This mineral coexists with calcite, dolomite, phlogopite, talc, dollaseite-(Ce), hematite, magnetite, chalcopyrite, and arsenopyrite. ## Localities The only confirmed occurrence of Åsgruvanite-(Ce) in the world is its type locality – the historical iron and copper mine Åsgruvan, located near Norberg in the Bergslagen region, Sweden.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the collector's value of Åsgruvanite-(Ce) primarily depends on the quality and richness of the microscopic specimen. Samples with well-formed, sharp crystals forming aesthetic, radial aggregates are most prized. The presence of associated minerals that create an attractive background for the main crystals is also important. Purity and intensity of color, although difficult to assess, also increase the specimen's value. ## Popular Localities The only source of specimens is the Åsgruvan mine in Sweden. Material for research and collecting comes from historical samples collected in this mine, which is currently inactive.

Care and storage

## Cleaning Specimens of Åsgruvanite-(Ce) should be handled with the utmost care. Due to the microscopic size of the crystals, mechanical cleaning is not recommended and can lead to their irreversible destruction. If dust removal is necessary, compressed air can be used from a safe distance. ## What to Avoid Avoid contact with all chemicals, including acids and strong bases, which may react with the complex composition of the mineral. Do not subject it to ultrasonic cleaning. Protect from high temperatures and humidity. ## Storage Micromineral specimens, such as Åsgruvanite-(Ce), are best stored in specialized, sealed "micromount" boxes, which protect them from dust, mechanical damage, and sudden changes in humidity.

Sources

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