Luanshiweiite

Chemical formula: KLiAl<sub>1.5</sub>(Si<sub>3.5</sub>Al<sub>0.5</sub>)O<sub>10</sub>(OH)<sub>2</sub>

Luanshiweiite is a rare mineral from the mica group, a lithium variety of muscovite, forming small, hexagonal flakes with a pearly luster.

## Characteristics Luanshiweite is a mineral from the mica group, belonging to the muscovite series. It occurs as very small, hexagonal or pseudohexagonal crystals with a platy appearance, usually not exceeding 0.3 mm. It forms aggregates in the shape of rosettes or irregular clusters. It is a transparent and colorless mineral, with a characteristic pearly luster on cleavage surfaces. ## Physical Properties This mineral is characterized by perfect cleavage in one direction, which is typical for micas. Its Mohs hardness ranges from 2 to 3, meaning it is very soft. The calculated density is 2.82 g/cm³. The luster is pearly on cleavage planes and vitreous on other surfaces. ## History and Name Luanshiweite was named in honor of Lu Anshiwei (born 1943), a Chinese mineralogist and professor at Peking University, in recognition of his contributions to mineralogy. The mineral was approved by the International Mineralogical Association (IMA) in 2017. The type locality where it was discovered is the Jiajika pegmatite in Sichuan Province, China.

Properties

Mohs hardness
2-3
Luster
Pearly
Streak
White
Density
2.82
Cleavage
Perfect on {001}
Fracture
Micaceous
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of luanshiweite requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (e.g., electron microprobe), due to its similarity to other micas, especially muscovite and trylithionite. Visually, it is recognized as a colorless mica with a platy habit. ## Distinguishing from Similar Minerals It is distinguished from muscovite and other light micas primarily by its chemical composition, specifically its high lithium content. Trylithionite, another lithium mica, has a similar composition but differs in structural parameters. Final differentiation is only possible through laboratory analysis. ## Crystal Forms Luanshiweite forms small, tabular, hexagonal or pseudohexagonal crystals. It occurs as individual flakes or aggregates resembling rosettes.

Geological environment

## Genesis Luanshiweite forms in granite pegmatites, rich in lithium and fluorine. It is a hydrothermal phase mineral, crystallizing in the late stages of pegmatite formation. ## Mineral Associations This mineral co-occurs with other minerals typical of lithium pegmatites, such as quartz, microcline, albite, spodumene, lepidolite, elbaite (a variety of tourmaline), and pollucite. ## Localities The only confirmed locality of luanshiweite in the world is its type locality - the Jiajika pegmatite field, in mine no. 134, Garzê Prefecture, Sichuan Province, China.

Rarity

Very rare

For collectors

## Quality Criteria As a "micromount" type mineral of scientific value, specimens with well-formed, euhedral crystals, clearly visible under magnification, are most prized. Association with other rare pegmatite minerals is also important. The purity and transparency of the flakes increase the specimen's value.

Care and storage

## Cleaning Luanshiweite specimens, due to their small size and delicacy, should be cleaned with the utmost care. It is best to use compressed air to remove dust. If wet cleaning is necessary, use distilled water and a very soft brush, avoiding the separation of the flakes. ## What to Avoid Avoid contact with chemicals, especially acids, which can damage the mineral's structure. As a very soft mineral, it is susceptible to scratches and mechanical damage. Protect it from ultrasound and sudden temperature changes. ## Storage It is recommended to store specimens in closed, padded collector's boxes to protect them from dust and physical damage. Due to the small size of the crystals, "micromount" type boxes are ideal.

Sources

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