Maohokite

Chemical formula: MgFe₃+₂O₄

Maohokite is a newly discovered, very rare mineral from the spinel group, found as microscopic inclusions in garnets from the Xiuyan deposit in China.

## Characteristics Maohokite is a magnesium and iron oxide belonging to the spinel group. It was identified as very fine, microscopic grains (from 5 to 30 micrometers) within pyrope-almandine crystals. Observed in reflected light, it is gray and appears opaque. Its discovery is scientifically significant as it represents the natural analogue of synthetic magnesium ferrite, a material with important magnetic properties. ## Physical Properties Due to the microscopic size of the grains, most physical properties of maohokite have not been directly measured, but rather calculated based on its chemical composition and crystal structure. The calculated density is 4.426 g/cm³. Hardness is estimated at approximately 7 on the Mohs scale, which is typical for minerals of the spinel group. The luster is described as metallic. ## History and Name The mineral was officially approved by the International Mineralogical Association (IMA) in 2018 under number IMA2017-071. The name "maohokite" honors Hok-kwang Mao (born 1941), a distinguished physicist and geochemist, for his fundamental contributions to high-pressure material research, including studies of Earth's mantle minerals. The discovery was made during the analysis of garnets originating from ultramafic rocks in the Xiuyan region of China. ## Uses Maohokite has no commercial or industrial applications due to its extreme rarity and microscopic size. Its significance is purely scientific and collectible, although specimens available to private collectors are practically nonexistent.

Properties

Mohs hardness: 7
Luster: Metallic
Density: 4.426
Cleavage: None
Transparency: Opaque
Crystal system: Cubic

Diagnostic features

## Identification Identification of maohokite is impossible without advanced laboratory techniques. It requires analysis using an electron microscope (EDS chemical composition analysis) and electron backscatter diffraction (EBSD) or X-ray diffraction to confirm the crystal structure. In reflected light, it appears as fine, gray, isotropic grains with a metallic luster. ## Distinguishing from Similar Minerals Maohokite is practically visually indistinguishable from other spinel-group oxides, such as magnetite, magnesioferrite, or chromite, which can form similar inclusions. Only quantitative chemical analysis provides a definitive distinction. ## Crystal Forms This mineral has been found exclusively as anhedral (irregular) or subhedral (poorly formed) grains of microscopic size, occurring as inclusions in garnets.

Geological environment

## Genesis Maohokite forms under high-pressure and high-temperature conditions, typical of ultramafic (silica-poor) rocks in deeper parts of the Earth's crust or in the upper mantle. Its presence in pyrope-almandine garnets indicates metamorphic or metasomatic processes occurring in such environments. It is an accessory mineral in magnesium- and iron-rich rocks. ## Mineral Associations This mineral co-occurs directly with garnet (pyrope-almandine), in which it forms inclusions. Other minerals found in the same rock include olivine, orthopyroxene, clinochlore, magnetite, and serpentine. ## Localities The only confirmed occurrence of maohokite worldwide (type locality) is the boron and iron deposit near Xiuyan, in Liaoning Province, northeastern China.

Rarity

Extremely rare

For collectors

## Quality Criteria Since maohokite occurs exclusively as microscopic inclusions, it has no significance as a standalone collector's specimen. The collectible value in this case is purely scientific and related to possessing a sample from the type locality containing an analytically confirmed mineral. Visual appeal applies only to the host mineral, i.e., garnet. ## Popular Localities The only source of material where maohokite has been identified is the type locality in Xiuyan, China. Specimens are not available on the commercial market.

Care and storage

## Cleaning Maohokite specimens occur as microscopic inclusions within other minerals (garnets) and do not require cleaning. Any cleaning applies only to the host mineral. ## What to Avoid Avoid any aggressive mechanical or chemical cleaning methods that could damage the surrounding garnet. Do not expose the specimen to strong acids or ultrasound. ## Storage Storage pertains to the host mineral. It should be protected from scratching by harder minerals and stored in stable conditions, away from dust and moisture.

Sources

IMA Mineral List (CNMNC)