Aluminocerite-(CeCa)

Chemical formula: (Ce₃+₆Ca₃)&#₉₇₄₄;Al(SiO₄)₃(SiO₃OH)₄(OH)₃

An extremely rare cerium, calcium, and aluminum silicate from the cerite supergroup, known from only one locality in the world.

## Characteristics Aluminocerite-(CeCa) is a very rare mineral belonging to the cerite supergroup. It forms small, poorly developed grains up to 1 mm in size, which can occur as aggregates. Its characteristic feature is its reddish-brown color. Due to its rarity and microscopic size, it is primarily of scientific interest and for specialized micromount mineral collectors. ## Physical Properties This mineral has a hardness of approximately 5 on the Mohs scale. It has a vitreous to greasy luster and is translucent. Its density, calculated based on the chemical formula and unit cell parameters, is 4.73 g/cm³. ## Colors and Varieties The only known color of aluminocerite-(CeCa) is reddish-brown. No color or commercial varieties have been distinguished. ## History and Name The mineral's name refers to its chemical composition – the presence of aluminum (Alumin-) and cerium (-cer-), with the suffix "-ite" characteristic of minerals. The -(CeCa) in parentheses is a Levinson modifier, indicating the dominant elements in specific positions of its crystal structure: cerium (Ce) and calcium (Ca). The mineral was officially recognized by the International Mineralogical Association (IMA) in 2007. The type locality (locus typicus), where it was discovered, is the Vostochnyi mine in the Khibiny Massif on the Kola Peninsula, Russia. ## Applications As an extremely rare mineral occurring only in the form of microscopic grains, aluminocerite-(CeCa) has no industrial applications. Its significance is purely scientific and for collectors.

Properties

Mohs hardness: 5
Luster: Vitreous to greasy
Streak: Light brown
Density: 4.73
Cleavage: None
Fracture: Uneven
Transparency: Translucent
Crystal system: Trigonal

Diagnostic features

## Identification Identification of aluminocerite-(CeCa) based on visual characteristics is impossible. Reddish-brown, poorly formed grains in a specific geological environment can only provide a clue. Definitive identification requires advanced analytical techniques, such as X-ray microanalysis (EDS/WDS) to determine chemical composition and X-ray diffraction (XRD) to confirm crystal structure. ## Distinguishing from Similar Minerals This mineral is visually indistinguishable from other members of the cerite group, such as cerite-(Ce) or ferricerite-(La). The differences lie in subtle changes in chemical composition (e.g., dominance of aluminum over iron), which can only be determined by laboratory methods. ## Crystal Forms Aluminocerite-(CeCa) does not form well-developed crystals. It occurs as subhedral (poorly formed) grains and their irregular aggregates.

Geological environment

## Genesis Aluminocerite-(CeCa) forms in the late stages of pegmatite crystallization within alkaline massifs. It is a product of hydrothermal processes in an environment rich in rare earth elements and simultaneously poor in silica. ## Mineral Associations This mineral occurs in association with other rare minerals typical of the Khibiny Massif. The most important associated minerals include aegirine, pectolite, lamprophyllite, lorenzenite, eudialyte, fluorapatite, mosandrite-(Ce), and belovite-(Ce). ## Localities The only confirmed locality for aluminocerite-(CeCa) in the world is its type locality – the Vostochnyi mine on Mount Koashva, within the alkaline Khibiny Massif, on the Kola Peninsula in Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare mineral, occurring exclusively in the form of micrograins, the main criterion for value is the certainty of identification confirmed by analyses. Collectors value specimens where aluminocerite-(CeCa) is as abundant and clearly visible as possible, as well as those that contain aesthetically pleasing crystals of associated minerals. The size of individual grains or their form is of secondary importance. ## Popular Localities All known specimens come from a single locality – the Vostochnyi mine in the Khibiny Massif in Russia. This is the only source of this mineral in the world.

Care and storage

## Cleaning Aluminocerite-(CeCa) specimens are typically micromounts, which are very delicate. Cleaning is not recommended. If absolutely necessary, compressed air (from a safe distance) can be used to remove dust. Any form of mechanical or chemical cleaning risks irreversible damage to the specimen. ## What to Avoid Avoid contact with harder minerals that could scratch it (hardness approx. 5). Do not expose it to acids or other chemicals. The effects of sunlight and humidity are unknown, but standard caution is recommended, as with other rare minerals. ## Storage The safest storage method is a specialized "micromount" box, which protects the specimen from dust, shocks, and mechanical damage. It should be stored under stable room conditions, away from direct sunlight.

Sources

IMA Mineral List (CNMNC)