Seifertite

Chemical formula: SiO<sub>₂</sub>

Seifertite is an ultra-high-density polymorphic variety of silicon dioxide, found mainly in Martian and lunar meteorites.

## Characteristics Seifertite is one of the densest and hardest known polymorphic varieties of silicon dioxide (SiO₂). It occurs as microscopic inclusions or thin lamellae within other minerals, such as stishovite, or in silica glass. Due to the extreme pressure conditions required for its formation, it does not form macroscopic crystals and is observed only in laboratory studies of meteorite samples. Its identification requires advanced analytical techniques, such as transmission electron microscopy (TEM) and electron diffraction. ## Physical Properties Seifertite is characterized by exceptional hardness, exceeding that of stishovite, and is the second hardest known oxide phase after diamond. Its density, approximately 4.35 g/cm³, is the highest among all SiO₂ polymorphs. It has a vitreous luster. These properties are a direct result of its compact crystalline structure, formed under pressures exceeding 40 gigapascals (GPa). ## Colors and Varieties Due to the microscopic size of its crystals, the color of seifertite observed under a microscope is usually colorless. No colored or commercial varieties are distinguished. ## History and Name The mineral was named in honor of Friedrich Seifert (born 1941), founder of the Bayerisches Geoinstitut in Bayreuth, Germany, in recognition of his contributions to experimental petrology and the study of minerals under high-pressure conditions. Seifertite was first identified in 2004 in the Martian meteorite Shergotty, which fell in India in 1865. Its discovery was made by Ahmed El Goresy and his collaborators. ## Applications Seifertite has no industrial or commercial applications. Its significance is purely scientific, providing key information about impact (shock) processes on planets and other celestial bodies, and about the behavior of silica under the extreme conditions found deep within the Earth's mantle.

Properties

Mohs hardness: >9
Luster: Vitreous
Streak: White
Density: 4.35
Cleavage: None
Fracture: Uneven
Transparency: Transparent
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of seifertite is impossible without specialized laboratory equipment. Identification relies on analyzing its crystal structure using electron diffraction in a transmission electron microscope (TEM) and on spectroscopic measurements (e.g., Raman spectroscopy). It occurs as microscopic lamellae within stishovite or silica glass in meteorites. ## Distinguishing from Similar Minerals Seifertite is most often confused with stishovite, another high-pressure SiO₂ polymorph. Differentiation is possible based on crystal structure analysis – seifertite has an orthorhombic structure, while stishovite has a tetragonal structure. Seifertite is also slightly denser than stishovite. Coesite, another SiO₂ polymorph, forms at much lower pressures and has a different structure (monoclinic). ## Crystal Forms Seifertite forms microscopic, elongated or platy crystals, often less than one micrometer in size. They occur as aggregates or individual lamellae crystallographically oriented within stishovite crystals.

Geological environment

## Genesis Seifertite is a mineral of shock metamorphism. It forms under extreme pressure conditions, estimated at over 40 gigapascals (GPa), and high temperatures, generated during the impacts of large meteorites on planetary surfaces. Such conditions correspond to the pressure found in the Earth's lower mantle. It has not yet been found in rocks on Earth, as the conditions for its formation are rare, and it is unstable and undergoes retrograde transformation to stishovite or coesite during exhumation to the surface. ## Mineral Associations This mineral co-occurs with other minerals of shock metamorphism. Its most common associate is stishovite, in which it often forms oriented lamellae. Other associated minerals include coesite, as well as minerals typical of Martian meteorites, such as pyroxene (pigeonite, augite), maskelynite (diaplectic plagioclase glass), and titanomagnetite. ## Localities Confirmed occurrences of seifertite are limited to a few meteorites. It was discovered in the Martian shergottite Shergotty (India). Its presence has also been confirmed in other Martian meteorites, such as Zagami (Nigeria), and in lunar meteorites, e.g., Dhofar 925 and 961.

Rarity

Extremely rare

For collectors

## Quality Criteria Seifertite is not a collector's mineral in the traditional sense. Its value is purely scientific. Specimens (meteorite fragments) containing seifertite are extremely valuable to research institutions and museums. Their value is determined by the confirmed presence of the mineral, its quantity, the quality of preservation of shock structures, and the provenance of the meteorite itself. ## Market Prices There is no trade in seifertite specimens. The prices of meteorite fragments in which it may occur depend on the type, size, and history of the meteorite, and not on the presence of seifertite itself, which can only be confirmed after purchase and destructive analysis of the sample in research. ## Popular Localities The most famous and first discovery site of seifertite is the Shergotty meteorite. Other important "sources" include the Martian meteorite Zagami and some lunar meteorites.

Care and storage

## Cleaning Specimens containing seifertite (meteorites) are extremely valuable and sensitive. They should not be cleaned outside of a specialized laboratory. Any attempt at cleaning may destroy or contaminate the microscopic mineral grains. ## What to Avoid Absolutely everything should be avoided: chemicals, water, ultrasonics, changes in temperature and humidity. These specimens are research material and should be handled with the utmost care. ## Storage Storage requires museum or laboratory conditions, preferably in sealed containers with a controlled atmosphere (e.g., dry nitrogen), to prevent oxidation and contamination. They should be protected from light, shocks, and all external factors.

External references

https://en.wikipedia.org/wiki/https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FSeifertite