Tianhuixinite

Chemical formula: (Mo⁶⁺O₃)₃·H₂O

Tianhuixinite is an extremely rare, naturally occurring molybdenum(VI) oxide, forming microscopic, acicular yellow crystals.

## Characteristics Tianhuixinite is a hydrated molybdenum(VI) oxide, occurring as extremely small, acicular or platy crystals. Individual crystals rarely exceed 0.2 mm in length and form radial or tangled aggregates. Due to its microscopic size, its visual characteristics are difficult to assess without specialized equipment. ## Physical Properties Crystals exhibit a luster described as vitreous to adamantine. They are elastic and flexible. Hardness and density have not been precisely measured due to the small size of the samples. ## Colors and Varieties Tianhuixinite has a characteristic, bright yellow color. No varieties are known. ## History and Name The mineral was approved by the IMA in 2022 (IMA2022-031). Its name honors Tianhui Ma (born 1964), a professor at Peking University, for his contributions to mineralogy and crystallography. It was discovered in the Lujing uranium mine in Guangdong Province, China. ## Applications Due to its extreme rarity and microscopic size, tianhuixinite has no industrial applications and is of scientific interest only, as well as for specialized collectors of rare minerals (so-called micromounts).

Properties

Mohs hardness
2-0
Color
dark blue-green
Luster
Vitreous to Adamantine
Streak
white
Density
4.131
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Translucent
Crystal system
Hexagonal

Diagnostic features

## Identification Practical identification of tianhuixinite is impossible without advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). Preliminary indications may include its bright yellow color, acicular crystal habit, and occurrence in the oxidation zones of uranium-molybdenum deposits. ## Differentiation from Similar Minerals It can be confused with other secondary molybdenum minerals, such as molybdite (MoO₃) or szenicsite (MoS₂), as well as other yellow secondary minerals from uranium deposits. Differentiation requires specialized laboratory analysis. ## Crystal Forms Tianhuixinite forms very fine, acicular or platy crystals that combine into radial, stellate, or haphazardly tangled aggregates.

Geological environment

## Genesis It is a secondary mineral, formed in the oxidation zone of hydrothermal uranium-molybdenum deposits. It results from the weathering of primary ores containing molybdenite. ## Mineral Associations It co-occurs with minerals such as quartz, fluorite, calcite, pyrite, molybdenite, uraninite, and other secondary uranium and molybdenum minerals. ## Localities The only confirmed locality worldwide (type locality) is the Lujing uranium mine, located in Wengyuan County, Shaoguan Prefecture, Guangdong Province, China.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a specimen depends on the richness and aesthetics of the microscopic aggregates on the host rock. Specimens with clearly formed, radial clusters of bright yellow needles, contrasting well with the matrix, are most valued. The overall size of the host rock is less important than the quality of the microcrystals themselves. ## Popular Localities The only source of specimens is the Lujing mine in China. Material from this locality is extremely difficult to acquire.

Care and storage

## Cleaning Tianhuixinite specimens are extremely delicate and usually occur as microscopic coatings or aggregates on the host rock. No mechanical or chemical cleaning is recommended. The safest way to remove dust is with compressed air from a safe distance. ## What to Avoid Avoid contact with water, chemicals, as well as any vibrations and impacts that could damage the fragile crystals. Do not expose the specimen to sudden temperature changes. ## Storage Specimens should be stored exclusively in specialized micromount boxes to protect them from dust, moisture, and mechanical damage. Display is only possible under a microscope.

External references

Sources

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