n.
A dense tetragonal polymorph of quartz that is formed under great pressure and is often associated with meteoroid impact.
[After Sergei Mikhailovich Stishov (born 1937), Russian mineralogist.]
stishovite
Dictionary:
stish·ov·ite (stĭsh'ə-vīt') 
|
n.
A dense tetragonal polymorph of quartz that is formed under great pressure and is often associated with meteoroid impact.
| 5min Related Video: stishovite |
| Sci-Tech Encyclopedia: Stishovite |
Naturally occurring stishovite, SiO2, is a mineral formed under very high pressure with the silicon atom in sixfold, or octahedral, coordination instead of the usual fourfold, or tetrahedral, coordination. The presence of stishovite indicates formation pressures in excess of 106 lb/in.2 (7.5 gigapascals). The possibility of the existence of stishovite at great depths strongly influences the interpretations of geophysicists and solid-state physicists regarding the phase transitions of mineral matter, as well as the interpretation of seismic data in the study of such regions of the interior of the Earth. See also Silica minerals.
Stishovite occurs in submicrometer size in very small amounts (less than 1% of the rock) in samples of Coconino sandstones from the Meteor Crater of Arizona, which contains up to 10% of coesite, the other high-pressure polymorph of silica. Because of its extremely fine grain size and because of the sparsity of this mineral in the rock, positive identification of the mineral is possible only by the x-ray diffraction method after chemical concentration. See also Coesite; Meteorite.
The specific gravity of stishovite, calculated from the x-ray data, is 4.28, compared with the value of 4.35 for the synthetic material. It is 46% denser than coesite and much denser than other modifications of silica. See also Rutile.
| Wikipedia: Stishovite |
| Stishovite | |
|---|---|
| General | |
| Category | Mineral |
| Chemical formula | SiO2 |
| Identification | |
| Color | Clear (when pure) |
| Mohs scale hardness | 9.4 |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 4.287 |
| Refractive index | nω = 1.81 |
| Melting point | 1650 (±75) °C |
Stishovite (after Sergey M. Stishov, a renowned Russian high-pressure physicist who first synthesized this mineral) is an extremely hard, dense tetragonal form (polymorph) of silicon dioxide. It was traditionally considered the hardest known oxide; however, boron suboxide was recently discovered to be much harder. At normal temperature and pressure, stishovite is metastable; it will eventually decay to quartz; however, this phase change is slow enough that it has never been observed. Stishovite was first found in nature and named after Stishov (who synthesized it earlier the same year) by Edward C. T. Chao.
Contents |
Synthesis
The only known occurrences of stishovite in nature formed at the very high shock pressures (>100 kbar or 10 GPa) and temperatures (> 1200°C) present during hypervelocity meteorite impact into quartz-bearing rock. Stishovite may also be synthesized by duplicating these conditions in the laboratory, either isostatically or through shock (see shocked quartz).[1]
With the density of 4.287 g/cm3, stoshovite is the heaviest polymorph of silica. It has tetragonal crystal symmetry, P42/mnm, No.136, Pearson symbol tP6.[2]
See also
- Coesite, a related mineral
References
External links
|
||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||
| This article about a specific silicate mineral is a stub. You can help Wikipedia by expanding it. |
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Learn More
 | silica (mineralogy) |
| Silica minerals (mineralogy and petrology) |
| Pyroxene (mineralogy and petrology) |
Post a question - any question - to the WikiAnswers community:
Copyrights:
 |
 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
 |
| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
 |
| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Stishovite". Read more |
ADVERTISEMENT
Mentioned in
- silica (mineralogy)
- Silica minerals (mineralogy and petrology)
- Pyroxene (mineralogy and petrology)
- High-pressure mineral synthesis
