Akaogiite

Chemical formula: Ti<sup>4+</sup>O<sub>2</sub>

Akaogiite is an extremely rare, high-pressure polymorph of titanium dioxide, occurring as microscopic grains in impact rocks.

## Characteristics Akaogiite is a naturally occurring, high-pressure polymorphic form of titanium dioxide (TiO₂). It occurs as extremely small, micrometer-sized grains that are invisible to the naked eye. It typically forms aggregates in association with graphite in rocks formed by meteorite impact. Due to the microscopic size of the crystals, most of its visual characteristics have not been determined. ## Physical Properties Most physical properties of akaogiite are impossible to determine by traditional methods due to the submicroscopic size of the grains. Hardness, luster, and transparency remain unknown. Its density has been calculated based on unit cell parameters and is approximately 4.73 g/cm³. ## Colors and Varieties The color of the mineral has not been determined. No varieties are known. ## History and Name Akaogiite was officially recognized as a new mineral by the International Mineralogical Association (IMA) in 2007. Its name honors Masaki Akaogi (born 1953), a Japanese professor from Gakushuin University in Tokyo, a specialist in mineral physics and high-pressure experiments, who first synthesized this phase in the laboratory. The type locality where it was first identified in nature is the Ries impact crater in Bavaria (Germany). ## Applications Akaogiite has no commercial or industrial applications. It is solely an object of scientific interest, providing information about the conditions prevailing during shock metamorphism in impact craters.

Properties

Density
4.73
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of akaogiite is only possible using advanced analytical techniques. Due to its microscopic size, it cannot be recognized visually. Key methods include X-ray diffraction using synchrotron radiation and chemical microanalysis (e.g., using an electron microprobe), which allow for the determination of its unique crystal structure and composition. ## Distinguishing from Similar Minerals Akaogiite is a polymorph of TiO₂, similar to rutile, anatase, and brookite. It differs from them in its crystal structure (baddeleyite-type), which is stable only under very high-pressure conditions. In field conditions or in a collection, it is indistinguishable without specialized equipment. ## Crystal Forms This mineral has so far only been found in the form of anhedral (irregularly shaped), microscopic grains ranging from 1 to 5 micrometers in size, often forming small aggregates.

Geological environment

## Genesis Akaogiite is a mineral formed under conditions of shock metamorphism, associated with large meteorite impacts. It forms as a result of the phase transformation of rutile or other TiO₂ polymorphs under extremely high pressures (above 10 GPa) and temperatures that prevail during such an event. ## Mineral Associations It occurs in paragenesis with other indicator minerals of shock metamorphism. At the type locality (Ries crater), it was found in association with graphite within glassy volcanic bombs in suevite. It may coexist with diamond and lonsdaleite. ## Localities Its occurrence has been confirmed in the Ries impact crater in Bavaria (Germany), which is its type locality. This is the only confirmed and thoroughly described natural occurrence of this mineral.

Rarity

Extremely rare

For collectors

## Quality Criteria Not applicable. Akaogiite is not a collectible mineral because it occurs only as microscopic inclusions invisible to the naked eye. Its value is purely scientific. ## Popular Localities There are no localities from which akaogiite specimens would be obtained for collecting purposes.

Care and storage

## Cleaning Not applicable. The mineral occurs as microscopic inclusions in the host rock and is not subject to cleaning. ## What to Avoid Scientific specimens containing akaogiite (so-called impactites) should be protected from chemical contamination that could interfere with future analyses. ## Storage Storage applies to the host rock (most often suevite) in which akaogiite is found. Such specimens are valuable research material and should be stored under stable conditions, in specialized containers, away from dust and moisture, preferably in the collections of scientific institutions.

External references

Sources

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