Aluminotaipingite-(CeCa)

Chemical formula: (Ce<sup>3+</sup><sub>6</sub>Ca<sub>3</sub>)Al(SiO<sub>4</sub>)<sub>3</sub>[SiO<sub>3</sub>(OH)]<sub>4</sub>F<sub>3</sub>

An extremely rare cerium, calcium, and aluminum silicate, approved as a new mineral in 2022, known only from the Bayan Obo mine in China.

## Characteristics Aluminotaipingite-(CeCa) is a complex silicate from the wikanite group, an aluminum-rich (aluminium) analogue of taipingite-(Ce). This mineral occurs as fine, anhedral (irregular) grains forming aggregates. Due to its recent discovery and extreme rarity, its properties have not yet been fully investigated. ## Physical Properties Specimens exhibit a vitreous luster and are translucent. Mohs hardness and density have not yet been determined. Data on cleavage and fracture type are also lacking. ## Colors and Varieties The mineral is characterized by a uniform, brownish color. The streak is light yellowish-brown. Currently, no other color varieties or commercial forms are known. ## History and Name Aluminotaipingite-(CeCa) was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2022 (IMA2022-092). Its name refers to its chemical composition – the dominance of aluminum (Alumino-) over iron compared to taipingite-(Ce) – and to the name of the parent mineral. The name "taipingite" comes from the nearby village of Taiping, located in the vicinity of the Bayan Obo mine. ## Applications Due to its extreme rarity and occurrence only as microscopic grains, aluminotaipingite-(CeCa) has no practical applications. It is solely an object of scientific and collecting interest.

Properties

Luster
Vitreous
Streak
Light yellowish brown
Transparency
Translucent
Crystal system
Trigonal

Diagnostic features

## Identification Visual identification is practically impossible and requires advanced analytical techniques, such as energy-dispersive spectroscopy (EDS/WDS) in an electron microprobe. In a collection, it can be recognized by its brownish color, vitreous luster, and occurrence as grain aggregates. However, the key indicator is a label from a trusted source and association with other minerals from Bayan Obo. ## Distinguishing from Similar Minerals It can be confused with many other brownish minerals with a granular structure, including other minerals from the wikanite group, such as taipingite-(Ce). Definitive differentiation is possible only based on chemical composition analysis. ## Crystal Forms This mineral does not form well-developed crystals. It occurs exclusively as anhedral (irregular) grains gathered in clusters (aggregates).

Geological environment

## Genesis Aluminotaipingite-(CeCa) forms in carbonatite deposits. It was discovered in dolomite-calcite veins cutting through a carbonatite massif. ## Mineral Associations This mineral occurs in association with aegirine, fluorite, barite, and calcite. ## Localities The only confirmed locality (type locality) in the world is the Bayan Obo iron and rare earth elements mine, in the Inner Mongolia Autonomous Region, China.

Rarity

Extremely rare

For collectors

## Quality Criteria For collectors, the most important criterion is an analytically confirmed identification of the specimen. The value is enhanced by the richness of aluminotaipingite-(CeCa) aggregates on the rock matrix and the presence of well-formed associated minerals. Due to its mode of occurrence, the aesthetics of the mineral itself (apart from color intensity) are of secondary importance. ## Popular Localities All specimens available on the collector's market come from a single location – the Bayan Obo mine in China. This is the only known locality for this mineral.

Care and storage

## Cleaning Utmost caution is recommended. To remove dust, use only compressed air or a very soft, dry brush. Do not use water, chemical solutions, or ultrasonic cleaners, as the chemical and physical stability of the mineral is unknown. ## What to Avoid Avoid contact with all chemicals, sudden temperature changes, and exposure to direct sunlight, which theoretically can affect minerals containing rare earth elements. Do not subject it to any mechanical tests. ## Storage Specimens should be stored under stable conditions, in specialized "micromount" boxes, away from moisture, dust, and temperature fluctuations. Proper labeling with location and confirmed identification is crucial.

Sources

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