Xieite

Chemical formula: Fe<sup>2+</sup>Cr<sup>3+</sup><sub>2</sub>O<sub>4</sub>

Xieite is a very rare iron chromium oxide from the spinel group, discovered in the Suizhou meteorite.

## Characteristics Xieite is an iron chromium oxide belonging to the spinel group. It occurs as extremely small, submicron-sized grains, typically anhedral (irregular) in habit, forming aggregates with other minerals. Due to the microscopic size of the crystals, its visual characteristics cannot be assessed with the naked eye. When observed under an electron microscope, it is gray in color and has a metallic luster. ## Physical Properties As an opaque mineral, xieite is characterized by a metallic luster. Its hardness and density have been calculated but not directly measured due to the microscopic size of the grains. The calculated density is approximately 4.52 g/cm³. ## Colors and Varieties The mineral is opaque, with a gray color in reflected light. No varieties are distinguished. ## History and Name The name xieite honors Xie Xiande (born 1934), a Chinese mineralogist and petrologist from the Institute of Geochemistry in Guangzhou, Chinese Academy of Sciences, for his contributions to the study of minerals in meteorites. The mineral was approved by the IMA in 2007, and its discovery was described in 2009. It was identified in the Suizhou chondrite meteorite, which fell in Hubei Province, China, in 1986. ## Uses Xieite has no commercial or industrial applications. Its significance is purely scientific, as an indicator of high-pressure and high-temperature conditions during the formation of meteorite parent bodies.

Properties

Luster
Metallic
Density
4.52
Cleavage
None
Transparency
Opaque
Crystal system
Cubic

Diagnostic features

## Identification Identification of xieite is only possible using advanced laboratory techniques, such as scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD). In reflected light, it is gray and isotropic. It cannot be identified based on macroscopic features. ## Differentiation from Similar Minerals Xieite is a polymorph of chromite with the same chemical formula (FeCr₂O₄) but a different, cubic crystal structure of the spinel type. Chromite crystallizes in the orthorhombic system. Distinguishing these two minerals requires structural analysis, e.g., using X-ray or electron diffraction. ## Crystal Forms This mineral forms anhedral (irregular), submicron grains, usually less than 10 micrometers in size, occurring in aggregates with other shock minerals.

Geological environment

## Genesis Xieite is a high-pressure mineral formed by shock metamorphism. It forms in shock veins within chondritic meteorites, which originated during asteroid collisions in space. Its formation conditions are estimated at a pressure of at least 20 GPa and a temperature of approximately 2000-2200 °C. ## Mineral Associations In the Suizhou meteorite, xieite coexists with other minerals such as chromite, ringwoodite, majorite, wadsleyite, and iron-nickel alloy (kamacite and taenite). ## Localities The only confirmed locality of xieite in the world is the Suizhou meteorite, which fell in 1986 near the city of Suizhou in Hubei Province, China. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, xieite is not traded by collectors as isolated specimens. The only way to possess it in a collection is to acquire a fragment of the Suizhou meteorite in which it has been identified. The value of such a specimen is determined by its mass, provenance, and quality as a meteorite specimen, not by the presence of xieite itself, which is impossible to verify without specialized equipment. ## Popular Localities The only source of xieite is the Suizhou meteorite from China.

Care and storage

## Cleaning Due to its microscopic size and occurrence solely as inclusions in meteorites, xieite specimens are not cleaned in the traditional sense. Preparation is limited to laboratory techniques used for the analysis of thin sections and polished sections. ## What to Avoid Specimens (meteorites) containing xieite should be protected from moisture, which can cause corrosion of associated minerals, especially metallic iron. Contact with chemicals and extreme temperatures should be avoided. ## Storage Meteorites containing xieite should be stored in dry conditions, preferably in specialized containers with a desiccant (e.g., silica gel), to prevent degradation.

External references

Sources

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