Akasakaite-(Ce)

Chemical formula: CaCe<sup>3+</sup>(Al<sub>2</sub>Mn<sup>2+</sup>)(Si<sub>2</sub>O<sub>7</sub>)(SiO<sub>4</sub>)O(OH)

Akasakaite-(Ce) is an extremely rare mineral of the epidote group, a complex cerium, calcium, aluminum, and manganese silicate, occurring as dark brown grains.

## Characteristics Akasakaite-(Ce) is a complex silicate from the epidote supergroup, with the chemical formula CaCe(Al₂Mn²⁺)(Si₂O₇)(SiO₄)O(OH). It occurs as very fine, irregular (anhedral) grains not exceeding 0.5 mm in size, which can form small aggregates. The mineral is dark brown to black and is opaque in mass, showing translucency only on very thin edges. ## Physical properties The mineral's Mohs hardness is 6. It has a vitreous luster and a light brown streak. The density calculated based on chemical composition and unit cell parameters is 4.11 g/cm³. It exhibits good cleavage in one plane. ## Colors and varieties The mineral is uniform in color, ranging from dark brown to black. No color varieties or commercial varieties are known. ## History and name Akasakaite-(Ce) was first described in 2014 by a team of mineralogists led by Daisuke Nishio-Hamane. Its name comes from its discovery locality in the Akasaka area (within the Fuka mine in Japan) and from the dominant rare earth element in its composition – cerium, which is indicated by the suffix -(Ce). ## Applications Due to its extreme rarity and occurrence as microscopic grains, Akasakaite-(Ce) has no industrial application. It is solely an object of scientific interest and a collector's item for specialized micromineral collectors.

Properties

Mohs hardness
6
Luster
Vitreous
Streak
Light brown
Density
4.11
Cleavage
Good on {001}
Transparency
Translucent to Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of Akasakaite-(Ce) based on visual characteristics is impossible. Due to its occurrence as fine, black grains, it requires advanced analytical techniques. Definitive identification is only possible through chemical analysis (e.g., using an electron microprobe - EDS/WDS) to confirm its unique composition, especially the presence and proportions of cerium, manganese, and aluminum. ## Distinguishing from similar minerals This mineral can be confused with other dark epidote-group minerals, such as allanite-(Ce), or with other rare manganese silicates. Certain differentiation from these requires specialized chemical and crystallographic analysis. ## Crystal forms Akasakaite-(Ce) forms exclusively irregular, anhedral grains up to 0.5 mm in size. Its occurrence as well-formed crystals has not yet been observed.

Geological environment

## Genesis This mineral forms under conditions of contact metamorphism. Its genesis is associated with high-temperature, low-pressure skarns that developed in Paleozoic limestones within metamorphosed manganese ore deposits. ## Mineral associations At the type locality, Akasakaite-(Ce) coexists with minerals such as celsian, anandite, cymrite, hedyphane, johannsenite, rhodonite, calcite, and quartz. ## Localities The only confirmed occurrence of this mineral in the world is its type locality – the Fuka mine, located in Bitchu-cho, Takahashi City, Okayama Prefecture on Honshu Island, Japan.

Rarity

Extremely rare

For collectors

## Quality criteria As a microscopic mineral, the collector's value of Akasakaite-(Ce) is determined by the certainty of its identification. The most valuable specimens are those where the mineral grains are clearly visible, as large as possible, and associated with other rare minerals from that locality. The richness of the aggregate and the aesthetics of the host specimen also enhance its attractiveness. ## Popular localities The only source of specimens is the Fuka mine in Japan. Material from this locality is highly prized by collectors specializing in rare minerals and microminerals.

Care and storage

## Cleaning Specimens of this mineral are typically microscopic grains on a host rock. Cleaning is not recommended and is usually not possible without specialized equipment. If dust removal is necessary, a photographic air blower can be used. ## What to avoid Avoid contact with chemicals, especially strong acids. Specimens should not be cleaned in ultrasonic cleaners. Protect them from shocks and mechanical damage. ## Storage The safest storage method is to place the specimen in a specialized micromount box, which protects it from dust, moisture, and physical damage.

Sources

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