coesite


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coesite

[′sē‚zīt]
(mineralogy)
A high-pressure polymorph of SiO2 formed in nature only under unique physical conditions, requiring pressures of more than 20 kilobars (2 gigapascals); usually found in meteor impact craters.
References in periodicals archive ?
The band with the maximum at about 670 [cm.sup.-1] can be correlated with strong line reported for coesite and having the maximum at 661[cm.sup.-1] [13].
The line 550 [cm.sup.-1] has the best correlation with coesite line centered around 522 [cm.sup.-1] [13].
The pyrope crystals are rich in interesting inclusions such as coesite (the monoclinic polymorph of quartz which formed at depths of some 100 km), two species for which this is the type locality (ellenbergerite, and magnesiodumortierite), and also bearthite, phosphoellenbergerite, zircon and monazite-(Ce).
Here coesite appears in larger nodules, up to a few millimeters in diameter, with its typical radial cracking.
leave the solution of cosmological problems to those learned in the infallible sacred texts.") Not until the discovery, several years later, that the "shock metamorphism" of large-body impacts (and nuclear explosions) can form two separate minerals, stishovite and coesite, and that many suspected impact sites had high concentrations of both, did the hypothesis begin to win converts.
When researchers recently fired single-wavelength beams of X rays and then laser light through two small crystals of coesite trapped in a Venezuelan diamond, the patterns of light scattering from the crystals revealed that the material's atoms are more closely packed than they are at atmospheric pressure.
Eclogite is a coarse-grained, attractively colored red-and-green rock consisting of about 50% garnet (almandine-pyrope) and 50% clinopyroxene, with minor rutile, kyanite, corundum and coesite; it is thought to result from profound metamorphism of subducted basalt under tectonically active margins of continental plates (basalt and eclogite are identical in their bulk chemistry--Kirkley et al., 1991).
The pyrope crystals are rich in interesting inclusions such as coesite (the monoclinic polymorph of quartz which formed at pressures higher than 25 kbar, corresponding to depths of some 100 kin), two species for which this is the type locality (ellenbergerite, and magnesiodumortierite) and also phosphoellenbergerite, bearthite, zircon and monazite-(Ce).
(1984) Coesite and pure pyrope in high-grade blueschists of the Western alps: a first record and some consequences.
DF died / fief DH dumdum / humhum DJ dingledangle / jinglejangle DL dowdy / lowly DN dogged / noggen DR dashed / rasher DT dread / treat DW dada / wawa DZ danda / zanza DG danda / ganga DI odd / oii DK deled / kelek DM daytide / Maytime DP daddies / pappies DS coedited / coesites DV dad / vav DY dawned / yawney