Lingunite

Chemical formula: NaAlSi₃O₈

Lingunite is a high-pressure polymorph of albite, occurring naturally in meteorites and serving as an important indicator of impact conditions.

## Characteristics Lingunite is a mineral from the tectosilicate group, representing a high-pressure polymorphic variety of albite. It occurs as microscopic grains and aggregates, typically less than 50 micrometers in size, embedded in impact-generated glass. Due to its size and mode of occurrence, its visual characteristics cannot be assessed with the naked eye. When observed under a microscope, it forms small, lath-like crystals. ## Physical Properties As a high-pressure mineral, lingunite is characterized by a significantly higher density (approximately 3.83 g/cm³) compared to albite (approximately 2.62 g/cm³). It is a transparent mineral with a vitreous luster. Its hardness has not been precisely measured due to the microscopic size of the crystals. ## Colors and Varieties Lingunite is colorless. No colored or commercial varieties are distinguished. ## History and Name The mineral was approved by the IMA in 2003. Its name honors Lin-gun "John" Teng (1936–1999), a geophysicist from the University of Southern California, for his contributions to research on mineral physics and impact processes. Lingunite was first identified in the Tenham meteorite, which fell in Australia (Queensland) in 1879. ## Applications Lingunite has no commercial or industrial applications. Its significance is purely scientific – it serves as a key indicator of the pressure and temperature conditions prevailing during meteorite impacts, helping to reconstruct the history of celestial body collisions.

Properties

Luster
Vitreous
Streak
White
Density
0
Cleavage
Good on {100} and {010}
Transparency
Transparent
Crystal system
Tetragonal

Diagnostic features

## Identification Identification of lingunite is only possible using advanced laboratory techniques, such as transmission electron microscopy (TEM) combined with electron diffraction and energy-dispersive spectroscopy (EDS) to confirm its chemical composition. Its extremely small size prevents identification in field conditions or using a standard petrographic microscope. ## Distinguishing from Similar Minerals Lingunite is distinguished from other NaAlSi₃O₈ polymorphs (such as albite or jadeite) based on its unique hollandite-type crystal structure, which can be identified by diffraction. From co-occurring shock minerals such as ringwoodite or maskelynite, it is distinguished by its chemical composition and characteristic structure. ## Crystal Forms Lingunite forms microscopic, lath-like or acicular crystals, often grouped into aggregates. These crystals typically do not exceed several tens of micrometers in length.

Geological environment

## Genesis Lingunite is a shock-metamorphic mineral, formed under extremely high pressures (above 21 GPa) and temperatures that occur during the impact of large meteorites on planetary surfaces. It forms as a result of the phase transformation of feldspar group minerals (mainly albite) contained in the impacting body or parent rock. ## Mineral Associations Lingunite occurs in shock veins in ordinary chondrites. It co-occurs with other high-pressure minerals such as ringwoodite, majorite, akimotoite, as well as maskelynite (diaplectic feldspar glass) and impact melt. ## Locations Its occurrence has been confirmed in several meteorites that experienced strong thermal-pressure shock. The main confirmed locations are the meteorites: - Tenham (Queensland, Australia) - type locality. - Sixiangkou (Anhui, China). - Suizhou (Hubei, China).

Rarity

Extremely rare

For collectors

## Quality Criteria Lingunite, as a microscopic mineral, is not an object of collector trade in the form of isolated crystals. The collector value lies in entire meteorite specimens in which its presence has been confirmed. In such cases, the value is determined by the type of meteorite, its history, size, and preservation quality, and the presence of lingunite constitutes a scientifically valuable curiosity, enhancing the uniqueness of the specimen. ## Popular Localities The most well-known source of lingunite are specimens of the Tenham meteorite from Australia, which is its type locality and where it was first described in detail.

Care and storage

## Cleaning Due to its microscopic size and occurrence within the rock matrix (meteorite), individual lingunite crystals are not subject to cleaning. Meteorite specimens containing lingunite should be handled according to general rules for extraterrestrial material. ## What to Avoid Extreme temperature changes that could affect the integrity of the entire meteorite specimen should be avoided. Samples should not be exposed to strong chemicals. As a high-pressure phase, lingunite is metastable under Earth's surface conditions and may transform into other phases under high temperatures (above 600°C). ## Storage Meteorite specimens containing lingunite should be stored under stable conditions, in a dry place, away from direct sunlight and contaminants. It is best to store them in dedicated containers or display cases for geological materials.

External references

Sources

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