Liudongshengite

Chemical formula: Zn<sup>2+</sup><sub>4</sub>Cr<sup>3+</sup><sub>2</sub>(OH)<sub>12</sub>(CO<sub>3</sub>)·3H<sub>2</sub>O

Liudongshengite is an extremely rare mineral from the hydrotalcite group, distinguished by its purple-red color and occurrence as hexagonal, platy crystals.

## Characteristics Liudongshengite is a hydrated zinc and chromium hydroxycarbonate, belonging to the hydrotalcite supergroup. It forms very small, thin, hexagonal crystals with a platy habit, which often combine into rosette-like or lamellar aggregates. Its most characteristic visual feature is its intense, purple-red color. ## Physical Properties This mineral is translucent and characterized by a vitreous luster, which transitions to pearly on perfect cleavage surfaces. Its density, calculated based on the chemical formula and unit cell parameters, is 2.89 g/cm³. The Mohs hardness has not yet been determined. ## Colors and Varieties The only known color of liudongshengite is purple-red. No color varieties or commercial varieties have been distinguished. ## History and Name The mineral is named in honor of Liu Dongsheng (1917–2008), a distinguished Chinese geologist and paleoclimatologist, considered the father of Chinese loess research. It was officially approved by the International Mineralogical Association (IMA) in 2019. The type locality, or first place of discovery, is the bauxite deposit in Wushan (Shanxi Province, China). ## Applications Due to its extreme rarity and occurrence as microscopic crystals, liudongshengite has no industrial applications. It serves solely as an object of scientific research and a valuable specimen in advanced systematic collections.

Properties

Luster
Vitreous, Pearly
Streak
Light pink
Density
2.89
Cleavage
Perfect on {0001}
Transparency
Translucent
Crystal system
Trigonal

Diagnostic features

## Identification The key diagnostic features of liudongshengite are its unique purple-red color, hexagonal, platy crystal habit, perfect cleavage in one direction, and a pale pink streak. Definitive identification is almost exclusively possible based on its locality – this mineral is known from only one place in the world. ## Distinguishing from Similar Minerals Liudongshengite can be confused with other minerals of similar color and habit. Stichtite (also from the hydrotalcite group) can be violet but contains magnesium instead of zinc and has a slightly different genesis. Cinnabar is much denser and has a bright red streak. Erythrite has a similar color but forms acicular crystals and is an arsenate. Final confirmation of identity requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Crystal Forms Crystals are in the form of thin, hexagonal plates, exhibiting excellent development of the basal pinacoid {0001}. They usually occur as aggregates resembling rosettes, fans, or stacks of thin lamellae.

Geological environment

## Genesis Liudongshengite is a secondary mineral, forming in the oxidation zone of chromium-enriched bauxite deposits. It forms as a result of hydrothermal or weathering processes acting on earlier chromium and zinc minerals. ## Mineral Associations At its occurrence, it is associated with minerals such as gibbsite, chromite, diaspore, calcite, and dolomite. ## Localities The only confirmed and described locality of liudongshengite in the world is its type locality – the chromium-bearing bauxite deposit in Wushan, Hequ County, Xinzhou Prefecture, Shanxi Province, China.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of specimens of this rare mineral is assessed based on several criteria. Those that display well-formed, sharp crystals with an intense, purple-red color are most highly valued. The aesthetics of the aggregates are also important – the more defined and visually attractive the rosettes, the more valuable the specimen. A contrasting matrix and the presence of well-formed associated minerals also increase its value. ## Popular Localities All known specimens of liudongshengite come from a single locality – the bauxite deposit in Wushan, China. This is the only locality from which collectors can acquire this mineral.

Care and storage

## Cleaning Liudongshengite specimens are typically microscopic and very delicate. For dust removal, it is best to use compressed air from a safe distance. Any mechanical cleaning (e.g., with a brush) is highly risky. If necessary, the specimen can be very carefully rinsed in distilled water and then immediately dried. ## What to Avoid The mineral is sensitive to acids, which cause its rapid dissolution. Contact with any chemicals should be avoided. Heating can lead to dehydration and destruction of the structure. Due to its perfect cleavage, it is very susceptible to mechanical damage. Prolonged exposure to strong sunlight should also be avoided. ## Storage The safest way to store specimens is to place them in a sealed "micromount" box, which protects them from dust, shocks, and mechanical damage. The box should be properly labeled.

Sources

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