Maoniupingite-(Ce)

Chemical formula: (Ce³⁺,Ca)₄(Fe³⁺,Ti⁴⁺,Fe²⁺,◻)(Ti⁴⁺,Fe³⁺,Fe²⁺,Nb⁵⁺)₄Si₄O₂₂

A black, opaque mineral from the chevkinite group, discovered in the Maoniuping rare earth element deposit in China.

## Characteristics Maoniupingite-(Ce) is a complex titanium, iron, and cerium silicate belonging to the chevkinite subgroup. It occurs as subhedral (poorly formed) grains ranging from 0.2 to 1.5 mm in size. It is an opaque mineral, black or brownish-black in color, with a resinous luster. ## Physical Properties Its Mohs hardness is 5 to 5.5. The measured density is 4.63 g/cm³. The mineral shows no cleavage, and its fracture is uneven. It is brittle and does not exhibit fluorescence under ultraviolet light. ## Colors and Varieties The observed colors are black and brownish-black. No named varieties of this mineral have been distinguished. ## History and Name The mineral's name comes from its discovery locality – the Maoniuping rare earth element deposit in Mianning County (Sichuan Province, China), which is also its type locality. The "-(Ce)" suffix in the name indicates cerium as the dominant rare earth element in its chemical composition. The mineral was officially approved by the International Mineralogical Association (IMA) in 2002. ## Uses Due to its rarity and microscopic size, maoniupingite-(Ce) has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized collectors of rare minerals or microminerals.

Properties

Mohs hardness
5-5.5
Luster
Resinous
Density
4.63
Cleavage
None
Fracture
Uneven
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of maoniupingite-(Ce) is impossible without advanced analytical techniques. It requires chemical analysis (e.g., using an electron microprobe) to confirm its complex composition with a dominance of cerium, titanium, and iron, and X-ray diffraction to determine its crystal structure. Visually, it is simply a "black mineral" in the rock. ## Distinguishing from Similar Minerals It can be confused with many other black, opaque minerals from the chevkinite group (e.g., chevkinite-(Ce), perrierite-(Ce)) and other titanosilicates and oxides (e.g., ilmenite, magnetite). Definitive distinction is only possible based on detailed laboratory analyses. ## Crystal Forms This mineral forms poorly developed, tabular grains, often occurring as small clusters or aggregates. Well-formed, idiomorphic crystals are not observed.

Geological environment

## Genesis Maoniupingite-(Ce) forms in hydrothermal processes. At its type locality, it was found in fluorite-barite-celestine veins that cut syenitic rocks. It is a product of alteration of earlier minerals under conditions enriched in rare earth elements. ## Mineral Associations This mineral co-occurs with minerals such as fluorite, barite, celestine, aegirine, monazite-(Ce), bastnäsite-(Ce), parisite-(Ce), thorianite, zircon, allanite-(Ce), and other minerals from the chevkinite group. ## Localities The only confirmed and described occurrence of maoniupingite-(Ce) in the world is its type locality – the Maoniuping rare earth element mine and deposit in Sichuan Province, China.

Rarity

Very rare

For collectors

## Quality Criteria The quality of maoniupingite-(Ce) specimens is assessed primarily from a scientific and micromineralogical perspective. The most desirable specimens are those where the mineral grains are as large as possible, clearly visible against a contrasting host rock (matrix), and occur in association with other rare minerals. A rich association of minerals on a single specimen significantly increases its value. ## Popular Localities The only source of specimens is the Maoniuping mine in China. Material from this locality is extremely difficult to acquire on the collector's market.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the microscopic size of the grains, mechanical or chemical cleaning is not recommended and may lead to damage or loss of material. ## What to Avoid Avoid contact with all chemicals, especially acids. Ultrasonic cleaners should also be avoided, as they can damage delicate grains embedded in the host rock. ## Storage Micromineralogical specimens should be stored in specialized "micromount" boxes, which protect them from dust and mechanical damage. Avoid exposure to extreme changes in temperature and humidity.

External references

Sources

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