Seifertite is a

silicate mineral Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

with the formula SiO₂ and is one of the densest polymorphs of

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

. It has only been found in

Martian Mars, the fourth planet from the Sun, has appeared as a setting in works of fiction since at least the mid-1600s. It became the most popular celestial object in fiction in the late 1800s as the Moon was evidently lifeless. At the time, the pr ...

and

lunar meteorite A lunar meteorite is a meteorite that is known to have originated on the Moon. A meteorite hitting the Moon is normally classified as a transient lunar phenomenon. Discovery In January 1982, John Schutt, leading an expedition in Antarctica fo ...

s, where it is presumably formed from either

tridymite Tridymite is a high-temperature polymorph of silica and usually occurs as minute tabular white or colorless pseudo-hexagonal crystals, or scales, in cavities in felsic volcanic rocks. Its chemical formula is Si O2. Tridymite was first describe ...

cristobalite Cristobalite is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the ...

– other polymorphs of

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

– as a result of heating during the atmospheric re-entry and impact to the Earth, at an estimated minimal pressure of 35 GPa. It can also be produced in the laboratory by compressing cristobalite in a

diamond anvil cell A diamond anvil cell (DAC) is a high-pressure device used in geology, engineering, and materials science experiments. It enables the compression of a small (sub-millimeter-sized) piece of material to extreme pressures, typically up to around 10 ...

to pressures above 40 GPa. The mineral is named after

Friedrich Seifert Friedrich Alfred Seifert (born 8 May 1941) is a German mineralogist and geophysicist. He is the founding director of Bayerisches Geoinstitut at University of Bayreuth. A silicate mineral, seifertite, is named after him. Life and work Seifert was b ...

(born 1941), the founder of the Bayerisches Geoinstitut at

University of Bayreuth A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, th ...

, Germany, and is officially recognized by the

International Mineralogical Association Founded in 1958, the International Mineralogical Association (IMA) is an international group of 40 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 5000 plus known mineral species. Th ...

.Seifertite: A new natural very dense post-stishovite polymorph of silica
University of Bayreuth. Seifertite forms micrometre-sized crystalline

lamellae Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology), a papery rib beneath a mushroom cap * Lamella (botany) * Lamella (surface anatomy), a plate-like structure in an animal * ...

embedded into a glassy SiO₂ matrix. The lamellae are rather difficult to analyze, as they vitrify within seconds under laser or electron beams used for standard

Raman spectroscopy Raman spectroscopy () (named after Indian physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman sp ...

or electron-beam microanalysis, even at much reduced beam intensities. Nevertheless, it was possible to verify that it is mainly composed of SiO₂ with minor inclusions of Na₂O (0.40 wt.%) and Al₂O₃ (1.14 wt.%).

X-ray diffraction X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

reveals that the mineral has

scrutinyite Scrutinyite is a rare oxide mineral and is the alpha crystalline form of lead dioxide (α-PbO2), plattnerite being the other, beta form. The mineral was first reported in 1988 and its name reflects the scrutiny and efforts required to identify i ...

( α-PbO₂) type structure with an orthorhombic symmetry and Pbcn or Pb2n

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it unchan ...

. Its lattice constants ''a'' = 4.097, ''b'' = 5.0462, ''c'' = 4.4946, ''Z'' = 4 correspond to the density of 4.294 g/cm³, which is among the highest for any forms of silica (for example, the density of quartz is 2.65 g/cm³).First page preview
Only stishovite has a comparable density of about 4.287 g/cm³.Stishovite summary
Handbook of mineralogy.

References

{{Silica minerals Silicate minerals Orthorhombic minerals Minerals in space group 60 Silica polymorphs

See also

References