Qilianshanite

Chemical formula: NaH₄(CO₃)(BO₃)·2H₂O

Qilianshanite is a very rare, hydrated sodium borocarbonate, forming colorless, platy crystals with a pearly luster.

## Characteristics Qilianshanite is a very rare mineral from the borocarbonate group. It occurs as small, colorless, platy or bladed crystals, which can form rosette-like aggregates. It is transparent and characterized by a vitreous or pearly luster, especially visible on cleavage planes. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of approximately 3. It is light, with a density close to 1.96 g/cm³. It exhibits perfect cleavage in one direction, which, combined with its softness, makes it very brittle and delicate. ## History and Name Qilianshanite was first described in 1964. Its name comes from its discovery locality – the Qilian Shan mountain range in Qinghai Province, China. This is the only confirmed occurrence of this mineral in the world. ## Uses Due to its extreme rarity and small crystal size, qilianshanite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and for scientists.

Properties

Mohs hardness
2
Color
Colourless
Luster
Vitreous, Pearly
Streak
White
Density
1.706
Cleavage
{100} and {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Qilianshanite is difficult to identify visually without specialized equipment. Key features include its occurrence in a specific geological environment (saline lakes), colorless, platy crystals with a pearly luster, perfect cleavage, and low hardness. Solubility in water is also a diagnostic feature. Final identification requires chemical analysis (EDS) or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other colorless, water-soluble evaporite minerals such as halite, trona, or borax. It is distinguished from them by its crystal habit (thin plates), specific chemical composition (it is both a borate and a carbonate), and crystallographic properties. ## Crystal Forms Crystals are usually very small, thin, and platy, with a hexagonal outline. They often form radial or rosette-like aggregates.

Geological environment

## Genesis Qilianshanite is an evaporite mineral. It forms by precipitation from highly saline, boron- and carbonate-rich waters of saline lakes under dry, desert climate conditions. It is a product of the final stages of evaporation. ## Mineral Associations This mineral co-occurs with other evaporites, such as northupite, thermonatrite, borax, and halite. It is found in clay sediments of dried saline lakes. ## Localities The only known and confirmed locality of qilianshanite in the world is its type locality: Da Qaidam (or Dachaidan) salt lake in the Qaidam Basin, Qilian Shan mountain range, Qinghai Province, China.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a qilianshanite specimen primarily depends on the size and development of the crystals and the richness of aggregates on the rock matrix. The most desirable specimens are those with distinct, sharp, transparent crystals forming aesthetic, rosette-like clusters. Due to its extreme rarity, any authentic specimen, even in micro form, is valuable to specialized collectors. ## Popular Localities The only source of specimens of this mineral is its type locality in China. Collector material is extremely rarely available on the market.

Care and storage

## Cleaning Qilianshanite specimens should be handled with the utmost care. Cleaning should be kept to an absolute minimum. If necessary, a very soft brush can be used to remove loose dust particles. Any contact with water should be avoided, as the mineral is soluble in it. ## What to Avoid Contact with water, acids, detergents, and all other chemicals must be strictly avoided. The mineral is sensitive to changes in temperature and humidity. It should not be exposed to direct sunlight or heated. ## Storage Qilianshanite requires storage under stable conditions. It is best kept in a sealed, closed "micromount" box away from sources of moisture and temperature fluctuations. Due to its fragility, it should be protected from shocks and vibrations.

External references

Sources

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