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Topic: Tridymite

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	TRIDYMITE (Silicon Dioxide)
		Most tridymite is believed to crystallize as beta tridymite which has an hexagonal symmetry and later as the crystal cools, it easily converts to tridymite.
		The conversion from beta tridymite to tridymite is so easy that the beta tridymite's hexagonal crystals are outwardly preserved in their original form.
		The presence of tridymite in a rock is helpful to petrologists (rock scientists) in determining the temperature of the rock at the time it crystallized.
	www.galleries.com /minerals/silicate/tridymit/tridymit.htm (631 words)

	Tridymite - LoveToKnow 1911
		TRIDYMITE, a mineral consisting of silicon oxide or silica, SiO 2, but differing from quartz in crystalline form.
		Tridymite occurs in the cavities of acid volcanic rocks (rhyolite, trachyte and andesite); the best-known localities are Cerro San Cristobal near Pachuca in Mexico, the Euganean Hills near Padua, and the Siebengebirge on the Rhine.
		Probably identical with tridymite is the form of silica known as asmanite, found in the meteorite which fell at Breitenbach,in the Erzgebirge, Bohemia.
	www.1911encyclopedia.org /Tridymite (169 words)

	Silica Minerals
		"tridymite is sometimes found as an essential constituent of acid effusives, associated in such manner with other minerals as to imply its separation from the melt as a primary constituent." I doubt very much whether tridymite is ever formed as a magmatic mineral.
		The "acid effusives" referred to by Fenner are the tridymite latites from the Creede district, Colorado, recently described by Emmons and Larsen.
		The tridymite latite is a dark red-brown banded rock with irregular streaks and lenses of a paler tint which are coarsely crystalline and contain abundant euhedral crystals of tridymite.
	www.minsocam.org /msa/collectors_corner/arc/silicamin.htm (4327 words)

	Digital Library of Ceramic Microstructures
		Tridymite is the only silica phase in this location and characterized by the presence of microcracks.
		The matrix between tridymite grains is rapidly crystallized wollastonite and glassy phase.
		Tridymite is still the only silica phase in this location and characterized by the presence of microcracks.
	www.udri.udayton.edu /dlcm/processsearch.asp?Material=516 (428 words)

	Siliocosis & Asbestosis (Site not responding. Last check: 2007-10-11)
		The commonest form of pneumoconiosis is due to the inhalation of free silica.
		A cryptocrystalline variety occurs in which the 'free silica' is bound to an amorphous silica (non-crystalline).
		Some of these forms can be altered by heat to the more dangerous crystalline varieties such as tridymite and cristobalite.
	www.healthandsafety.co.uk /silasb.htm (734 words)

	Artemis Project: Silica Minerals
		Cristobalite and tridymite are often found together in mare basalts.
		Cleavage is absent, except for tridymite which may exhibit a poor prismatic cleavage.
		Tridymite has been crystallized from silica gel in the presence of fluorides and carbonates of K and Na.
	www.asi.org /adb/m/05/01/04/silica.html (559 words)

	Iran Mineral Export, Silica Sand (Site not responding. Last check: 2007-10-11)
		The artificial minerals are the principal constituents of silica bricks,7 which are made by burning ground-up quartzites containing from 97 to 98 per cent of silica.
		While amorphous silica can be transformed into crystalline forms such as tridymite and cristobalite by heating to high temperatures (approximately 870° and 1470° respectively), it is generally only the crystalline forms of silica which are fibrogenic.
		The temperature at which amorphous silica can be converted to crystalline forms such as tridymite and cristobalite is very dependent upon pressure and chemical environment.
	www.mineralco.net /silica/silica-sand.htm (9538 words)

	FD1
		Figure 4 shows the crystal structures of tridymite and cristobalite viewed perpendicular to the polyhedral layers, for comparison with your models.
		Transitions between high quartz, high tridymite, and high cristobalite are reconstructive, and therefore it is possible to preserve tridymite and cristobalite on quenching to room temperature.
		Hence determine the relative susceptibilities of tridymite and cristobalite to cracking during heat–cool cycles.
	www.msm.cam.ac.uk /phase-trans/abstracts/GD3.htm (1492 words)

	Bibliography on Opal, cristobalite and related literature
		Friedlaender, C. Entaxy of tridymite in the gangue of a Pb-Cu-Zn-occurrence.
		Gibbs, R. The polymorphism of silicon dioxide and the structure of tridymite.
		Nakui, A., Yamamoto, A., and Nakazawa, H. Non-integral phase in tridymite.
	www.osha.gov /SLTC/silicacrystalline/smithdk/ref.html (4891 words)

	Iran Mineral Export, Silica (Site not responding. Last check: 2007-10-11)
		According to Fenner16 "tridymite is sometimes found as an essential constituent of acid effusives, associated in such manner with other minerals as to imply its separation from the melt as a primary constituent." I doubt very much whether tridymite is ever formed as a magmatic mineral.
		The "acid effusives" referred to by Fenner are the tridymite latites from the Creede district, Colorado, recently described by Emmons and Larsen.17 Concerning these rocks it is said that the "tridymite forms in large part during the later stages of the crystallization of the groundmass."
		The presence of 0.01% Al2O3 lowers the refractoriness of silica by 4.8ºF and 0.4% of Al2O3 by 140ºF. Silica-rock of metamorphic origin is better than that of igneous origin because silica grains cemented with cristobalite and tridymite are stable phases of silica.
	www.bentonite.biz /silica1.asp (13289 words)

	WOHL: Sample Analysis: Silica by X-ray (Site not responding. Last check: 2007-10-11)
		WOHL performs analysis for crystalline free silica including quartz, cristobalite, and tridymite via X-ray diffraction based on OSHA ID-142.
		WOHL uses 3 separate peaks for the determinations of both quartz and cristobalite, and 2 separate peaks for the determination of tridymite.
		The reporting levels (RL) are: for quartz RL = 10 ug/sample, for cristobalite RL = 20 ug/sample, and for tridymite RL = 20 ug/sample.
	www.slh.wisc.edu /wohl/analysis/silica.php (88 words)

	[No title] (Site not responding. Last check: 2007-10-11)
		Intermediate in density and position between the crust and core is the mantle, composed of intermediate density silicate minerals such as olivine and pyroxene.
		For example, diamond is stable only at very high pressures and tridymite is only stable at low pressures and high temperatures.
		When minerals such as these are found in rocks we are able to place limits on the range of temperature and pressure under which the rocks must have formed.
	darkwing.uoregon.edu /~jrice/geol_311/Midtermkey.html (1072 words)

	IRMI - Silicaâ€”The Next Environmental Issue
		The "rock" sandstone is composed of quartz and can be found in many areas throughout the country except for southern coastal areas where most beaches are made up of limestone.
		Tridymite and crystobalite are simply polymorphs of quartz.
		Tridymite, while somewhat rare, can be found in many volcanic rocks.
	www.irmi.com /Expert/Articles/2005/Slivka04.aspx (2895 words)

	TRIDYMITE - Online Information article about TRIDYMITE
		Unlike quartz, it is soluble in a boiling See also:
		Tridymite occurs in the cavities of See also:
		Probably identical with tridymite is the form of silica known as asmanite, found in the See also:
	encyclopedia.jrank.org /TOO_TUM/TRIDYMITE.html (241 words)

	Tridymite Mineral Data
		Comments: Clear, pseudohexagonal crystals of tridymite on matrix.
		Dollase W A, Baur W H, American Mineralogist, 61 (1976) p.971-978, The superstructure of meteoritic low tridymite solved by computer simulation
		Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.
	webmineral.com /data/Tridymite.shtml (177 words)

	Masonry Magazine: Government Affairs
		Cristobalite and tridymite are forms of crystalline silica, less abundant than quartz, that have lower PELs than quartz.
		OSHA PELs for respirable crystalline silica, expressed in milligrams of respirable dust per cubic meter of air (mg/m3) are as follows:
		Tridymite: Use 1/2 the value calculated from the above mass formula for quartz.
	www.masonrymagazine.com /11-02/gov.html (1271 words)

	Tridymite
		English words defined with "tridymite": silica, silicon dioxide, silicon oxide.
		Specialty definitions using "tridymite": lussatite &diams; quartz latite.
		Words rhyming with "tridymite" (pronounced '*Trid"ymite**'): Ammite, Atacamite, Azymite, Benjamite, Bismite, Calamite, Catamite, Chromite, Dynamite, gummite, mite, Ophthalmite, osmite, Ottomite, Palmite, Pandermite, Pentremite, Podophthalmite, Protosomite, Psammite, samite, Sclerodermite, somite, stalagmite, termite, Zamite.
	www.websters-online-dictionary.org /tr/tridymite.html (231 words)

	Wannenköpfe (Site not responding. Last check: 2007-10-11)
		Tridymite has (just like Cristobalite) the same chemistry as Quartz...
		The most interesting twins are the six rayed trillings or triplets from where Tridymite gets its name.
		Till about a week ago I was sure I had just only a few Tridymites in my Wannenkopf collection...
	wannenkopfe.strahlen.org /tridymite.html (133 words)

	Digital Library of Ceramic Microstructures
		SEM_BSE microstructure of GEN-SIL silica brick after creep test showing "fish-scale" type internal texture of cristobalite grains enclosed in glass matrix.
		These Cristobalite islands are derived from original Tridymite + Glass mtrix of the brick.
		The microstructure contains large Cristobalite islands with fish-scale texture bonded with prismatic Tridymite and Glass.
	www.udri.udayton.edu /dlcm/processsearch.asp?Material=485 (298 words)

	eMedicine - Silicosis : Article Excerpt by: Basil Varkey, MD, FRCPC, FCCP
		Background: Pneumoconiosis is the general term for lung disease caused by inhalation of mineral dust.
		Silicosis is a fibronodular lung disease caused by inhalation of dust containing crystalline silica (alpha-quartz or silicon dioxide), which is distributed widely, or its polymorphs (tridymite or cristobalite), which are distributed less widely.
		Quartz, the most common form of crystalline silica, is abundantly present in granite, slate, and sandstone.
	www.emedicine.com /med/byname/silicosis.htm (692 words)

	Silica - Silicon Dioxide (SiO2) (Site not responding. Last check: 2007-10-11)
		There are three crystalline forms of silica; quartz, tridymite, cristobalite and there are two variations of each of these (high and low.)
		Upon heating up to high temperatures the quartz will transform to tridymite and cristobalite.
		In bricks tridymite tends to be the most favourable of all crystalline forms of silica, as it has a smooth, predictable and low thermal expansion up to 600°C.
	www.azom.com /details.asp?ArticleID=1114 (1418 words)

	Heribert Graetsch (Site not responding. Last check: 2007-10-11)
		Graetsch (2000): Two forms of aluminium phosphate tridymite, from X-ray powder data.
		H.A. Graetsch (2001): Hexagonal high-temperature form of aluminium phosphate tridymite from x-ray powder data.
		H.A. Graetsch (2002): Monoclinic AlPO4 tridymite at 473 and 463 K from powder data.
	www.ruhr-uni-bochum.de:8043 /eng/leute/graetsch.html (171 words)

	Emission spectroscopy of silica (Site not responding. Last check: 2007-10-11)
		To that end, it is important to understand the thermal infrared spectral properties of the silica phases so that we can more clearly understand spectral information returned from Mars.
		We collected natural samples of opal, opal-CT, and tridymite.
		We couldn't find any coarse (sand sized) coesite and cristobalite that is reasonably pure, so we synthesized those minerals.
	www.public.asu.edu /~jmichal/research/silica.html (553 words)

	AMCSD Search Results
		The superstructure of meteoritic low tridymite solved by computer simulation
		of SiO2 tridymite between 110 and 220 C
		Multiple datasets can be concatenated into a single downloadable file by selecting the datasets and then hitting the "Process Selected Data" button.
	rruff.geo.arizona.edu /AMS/result.php?mineral=Tridymite (145 words)

	Tridymite: Tridymite mineral information and data.
		There is no specific data on health dangers or toxicity for this mineral, however you should always treat mineral samples as potentially toxic/dangerous and use sensible precautions when handling them.
		Lukesh, Joseph & Martin J. Buerger (1942), The tridymite problem (abstract): American Mineralogist: 27: 143.
		Mitchell, R.S. (1967), Tridymite pseudomorphs after wood: In: Virginian Lower Cretaceous sediments: Science: 158: 905-906.
	www.mindat.org /min-4015.html (320 words)

	[No title] (Site not responding. Last check: 2007-10-11)
		Note that although this arrangement might seem similar to (SiO
		tetrahedra in the cyclosilicates, in tridymite each six-sided ring is linked to those of the sheet above andf below (in cyclosilicates, each tetrahedra of a given ring 'points' in the same direction.
		Tridymite is common in certain siliceous volcanic rocks.
	www.auburn.edu /~hameswe/Tridy_Cristobpage.html (137 words)

	old exam
		How would you use a microscope to compare the birefringence of the two minerals?
		One way to distinguish quartz from tridymite in thin section is to compare relief.
		How can we talk about relief when we look at a thin section--don't we always make thin sections the same thickness?
	www.und.nodak.edu /instruct/mineral/geol318/oldexams/exam1-96.htm (751 words)

	Spherical / Round Silica (Si02) From READE
		silica, silicon dioxide, quartz, spherical, round, bead, ball, white, unground, cristobalite, tridymite
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		silica, silicon dioxide, quartz, spherical, round, bead, ball, white, unground, cristobalite, tridymite, silica, silicon dioxide, quartz, spherical, round, bead, ball, white, unground, cristobalite, tridymite, silica, silicon dioxide, quartz, spherical, round, bead, ball, white, unground, cristobalite, tridymite
	www.reade.com /Products/Oxides/spherical_round_silica_quartz_sand.html (230 words)

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