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	CRISTOBALITE (Silicon Dioxide)
		Cristobalite is common in volcanic rocks and many microscopic crystals are easily seen in a petrographic microscope.
		Most cristobalite is believed to crystallize as beta cristobalite which has an isometric symmetry and later as the crystal cools, it easily converts to alpha cristobalite or just cristobalite.
		The conversion from beta cristobalite to cristobalite is so easy that the beta cristobalite's isometric crystals are outwardly preserved in their original form.
	mineral.galleries.com /minerals/silicate/cristoba/cristoba.htm (560 words)

	United States Patent Application: 0030109624
		The composition of claim 5 wherein said cristobalite silica is a powder with mean particle size of from 1 to 3 micrometers and maximum particle size of 25 micrometers and wherein the amount of said cristobalite silica is 9% to 16% by weight based on the weight of said composition.
		Cristobalite silica is preferably added during a time when the reaction mixture has low enough viscosity to be stirred, so that the cristobalite silica can be mixed with the other components.
		Cristobalite silica may be added to the RP prepolymer in the same manners and amounts as in the one- and two-stage processes.
	appft1.uspto.gov /netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/PTO/search-bool.html&r=1&f=G&l=50&co1=AND&d=PG01&s1=20030109624.PGNR.&OS=DN/20030109624&RS=DN/20030109624 (3721 words)

	Method for producing unsintered cristobalite particles - Patent 5154905
		Such cristobalite is used as a filler, a dispersing agent, etc., and also as a material for high-quality artificial quartz, ceramics, etc., and particularly as a material for transparent quartz glass because of its generating no bubbles at the time of melt-molding.
		Cristobalite obtained by the present invention is used as a filler, a dispersing agent, etc., and also can preferably be used as a material for high-quality artificial quartz, ceramics, etc., and particularly as a material for transparent quartz glass because of its generating no bubbles at the time of melt-molding.
		For this reason, preferred cristobalite particles for addition and mixing is such finely divided particles that their particle size is in a range of preferably 10 to 400.mu.m, more preferably 10 to 200.mu.m, though these cristobalite particles may contain finely divided particles of less than 10.mu.m in particle size in substantially ignorable amounts.
	www.freepatentsonline.com /5154905.html (5213 words)

	Search Results for cristobalite - Encyclopædia Britannica
		Cristobalite is probably more abundant in nature than tridymite, although it seldom forms as distinctive crystals.
		a widespread silica mineral, the fibrous variety of low-temperature cristobalite (compare opal) that occurs with opal and chalcedony near the surface of low-temperature hydrothermal deposits.
		In diagrams of pressure-temperature fields of stability of silica minerals, stability fields are not shown for keatite, melanophlogite, opal, or the low forms of tridymite and cristobalite because...
	www.britannica.com /search?query=cristobalite&submit=Find&source=MWTEXT (313 words)

	Silica (IARC Summary & Evaluation, Volume 68, 1997)
		Cristobalite exposure is notably associated with the use and calcination of diatomaceous earth as well as refractory material installation and repair operations.
		After calcination (which significantly increases the cristobalite content), diatomaceous earth is used as a filtration agent, carrier for pesticides, filler in paints and paper and as a refractory or abrasive product in a variety of industries.
		In a cohort study of British pottery workers, lung cancer mortality was slightly elevated; a nested case-control analysis of lung cancer did not show an association with duration of exposure, but indicated a relationship between lung cancer mortality and average and peak exposures in firing and post-firing operations, with relative risks of approximately 2.0.
	inchem.org /documents/iarc/vol68/silica.html (2652 words)

	HYDROTHERMAL ALTERATION
		Cristobalite is the dominant polymorph in Units 5 and 6, whereas quartz and cristobalite are both present in significant quantities in Units 8 and 10.
		Cristobalite is the dominant polymorph of silica in Unit 11, whereas quartz predominates in Unit 13.
		Cristobalite is the dominant silica polymorph at the top of the interval, but quartz dominates in the lower portion.
	www-odp.tamu.edu /publications/193_IR/chap_03/c3_3.htm (9001 words)

	Rocks & Minerals: An Occurrence Of Cristobalite In Adirondack Garnet - Brief Article
		It is most remarkable that the cristobalite did not later transform reconstructively to beta quartz following the peak of the Adirondack metamorphism because the temperature stayed in excess of 600 [degrees] C for 50-100 million years (Mezger et al.
		The presence of cristobalite in Adirondack garnet represents an extraordinary case of mineral preservation, and its apparent widespread occurrence suggests that it may form in high-grade metamorphic rocks worldwide.
		An occurrence of metastable cristobalite in high-pressure garnet granulite.
	www.findarticles.com /p/articles/mi_m0GDX/is_3_74/ai_58915125 (528 words)

	Polymorphs of Quartz
		Cristobalite is yet another natural form of silica.
		It is stable at temperatures below 514º F (268º C), and at temperatures between 3142º F and 2678º F (1470º C and 1470º C) it is Beta Cristobalite, in a stable form (with a different crystal structure).
		Cristobalite specimens are all paramorphs of Beta Cristobalite, and, although tetragonal, retain Beta Cristobalite's original isometric shape.
	www.minerals.net /mineral/silicate/tecto/quartz/sio2poly.htm (751 words)

	Summary of the findings of studies undertaken to investigate the effects of exposure to volcanic ash on Montserrat : ... (Site not responding. Last check: 2007-10-02)
		The cristobalite content of ash varies: the proportion of the silica which is present as cristobalite increasing with the period for which it has been exposed to high temperatures.
		The cristobalite content of the ash is clearly likely to be important but so is the distribution of particle size in the ash as this will control the likelihood of the ash particles being inhaled deeply into and being deposited, in the lungs.
		It was noted that, with regard to an inflammatory response, 1 mg of cristobalite produced an earlier response than 5 mg of ash though by 49 weeks the response to 1 mg of cristobalite had declined and the response to 5 mg of ash had become significant.
	www.dh.gov.uk /PublicationsAndStatistics/Publications/PublicationsPolicyAndGuidance/PublicationsPolicyAndGuidanceArticle/fs/en?CONTENT_ID=4103106&chk=7EWJ1m (4573 words)

	Toxicologic Review of Selected Chemicals (Site not responding. Last check: 2007-10-02)
		limit, adopted in 1985, does not reflect a re-evaluation of cristobalite's toxicity but was adopted merely to simplify the monitoring of cristobalite dust concentrations.
		Experimental animals injected with cristobalite showed a more severe response than that produced by quartz, and the fibrosis that followed was diffuse rather than nodular.
		Cristobalite, one of the three major forms of silicon dioxide, is transparent, tasteless, and stable at high temperatures.
	www.cdc.gov /NIOSH/pel88/14464-46.html (300 words)

	Martin Dove: Studies of the phase transition in cristobalite
		Cristobalite is a form of SiO2 with a relatively simple crystal structure that is closely related to the diamond structure.
		Rigid Unit Mode model) to investigate the dynamics and correlations in the cubic phase of cristobalite.
		We use high-resolution neutron diffraction to measure the structure as a function of temperature, and we show that the phase transition can be accurately described within the formalism of Landau theory in spite of the large first-order discontinuity at the phase transition.
	www.esc.cam.ac.uk /astaff/dove/cristobalite.html (888 words)

	1999 Building Publications - Quantitative X-Ray Diffraction Analysis of Handmolded Brick. (Site not responding. Last check: 2007-10-02)
		It has been proposed that the ratio of cristobalite to quartz would be a reliable predictor of durability.
		The intensities of the cristobalite, quartz, and corundum peaks were calculated after correcting for background.
		Consequently, the cristobalite index may be usable only for bricks with chemical compositions similar to those of Colonial Williamsburg.
	fire.nist.gov /bfrlpubs/build99/art097.html (282 words)

	Investments for dental casting - Patent 4604142
		However, further addition of a small amount of soluble starch improves the "wettability" of the investment material slurry with respect to the wax pattern, and functions to divide the crystals of hemihydrate gypsum growing at the contact portion of the wax pattern with the investment material.
		Out of these, quartz and cristobalite are refractory materials, while hemihydrate gypsum acts as a binder for affording molding capacity and strength to such investment materials.
		Hemihydrate gypsum, quartz and cristobalite were weighed according to the proportions as specified in the table, and were mixed together in a mortar to prepare investment materials.
	www.freepatentsonline.com /4604142.html (1881 words)

	QUARTZ AND CRISTOBALITE IN WORKPLACE ATMOSPHERES - (Inorganic Method #142)
		Cristobalite is used in the manufacture of insulation, filters, and refractory materials (8.8.
		Both cristobalite and tridymite can be found naturally occurring in volcanic rock or can be synthetically produced by heating amorphous or crystalline silica.
		Cristobalite has fewer useful analytical diffraction peaks than quartz, is more prone to form distorted crystallites, and therefore more prone to interference problems.
	www.osha.gov /dts/sltc/methods/inorganic/id142/id142.html (6952 words)

	Digitalfire Material Database: Cristobalite (Site not responding. Last check: 2007-10-02)
		Cristobalite forms spontaneously at temperatures above 1100C from very fine quartz found in some clays, from finely ground silica, and from molecular silica liberated during the formation of mullite from kaolin.
		Some clays generate so much cristobalite that they will litterally shed all of their glaze during final stages of cooling.
		This approach is necessary in low temperature ware because quartz inversion at 573C typically finds glazes still somewhat fluid, having not reached their set point (quartz inversion is used to advantage to put high temperature glaze in final compression).
	digitalfire.com /material/m-01k131.htm (440 words)

	Artemis Project: Silica Minerals
		The most common silica in mare basalt is cristobalite.
		Cristobalite and tridymite are often found together in mare basalts.
		Fine grained basalts tend to have cristobalite and quartz.
	www.asi.org /adb/m/05/01/04/silica.html (559 words)

	Thermal Properties
		In general, the devitrification rate of fused quartz is slow for two reasons: the nucleation of the cristobalite phase is possible only at the free surface, and the growth rate of the crystalline phase is low.
		In certain applications, devitrification can be put to the user's advantage since the cristobalite tends to inhibit sag of the fused quartz.
		For example, if a diffusion furnace tube is to be used at high temperatures for extended periods of time, and is not subject to thermal cycling below the beta to alpha cristobalite transformation, rotation procedures have been found to be beneficial.
	www.gequartz.com /en/thermal.htm (1011 words)

	Cristobalite (from silica mineral) -- Britannica Concise Encyclopedia - The online encyclopedia you can trust!
		The devitrification (transformation from the glassy to the crystalline state) of siliceous volcanic glasses yields abundant tiny crystallites of cristobalite, and the mineral is also deposited metastably from hot hydrous gases in cavities and cracks of many volcanic rocks.
		More results on "Cristobalite (from silica mineral)" when you join.
		Cristobalite has two modifications: low-cristobalite, which occurs naturally up to 268° C (514° F) but is not stable; and high-cristobalite, which occurs above 268° C but is only stable above 1,470° C. silica
	www.britannica.com /ebc/article-80056?tocId=80056 (820 words)

	clayart - thread 'cristobalite in low clay' (Site not responding. Last check: 2007-10-02)
		First of all cristobalite starts to form when mullite starts to form.
		cristobalite but it was there because it was in the grog.
		I have also found cristobalite in cone 6 bodies.
	www.potters.org /subject02424.htm (305 words)

	Pulmonary epithelial response in the rat lung to instilled Montserrat respirable dusts and their major mineral ...
		Bioreactivity of the cristobalite (and quartz) is therefore
		Cristobalite in volcanic ash of the Soufriere Hills volcano, Montserrat, British West Indies.
		Opal, cristobalite and tridymite: noncrystallinity versus crystallinity, nomenclature of the silica minerals and bibliography.
	oem.bmjjournals.com /cgi/content/full/59/7/466 (3509 words)

	IARC Reevaluates Silica and Related Substances (Site not responding. Last check: 2007-10-02)
		Intrapleural injection of cristobalite and tridymite with particles in the respirable range also resulted in malignant lymphomas (primarily of the histiocytic type) in three studies in rats.
		Mechanistic evidence suggests that the development of lung tumors in rats in response to crystalline silica (quartz) is the result of marked and persistent inflammation and epithelial proliferation; however, a role for surface-generated oxidants or even a direct genotoxic effect cannot be ruled out.
		The final conclusion based upon all the available data was that crystalline silica inhaled in the form of quartz or cristobalite from occupational sources is carcinogenic to humans (Group 1) and that amorphous silica is not classifiable as to its carcinogenicity to humans (Group 3).
	ehp.niehs.nih.gov /members/1997/105-7/wilbourn-full.html (2900 words)

	APStracts 5:0190L, 1998. (Site not responding. Last check: 2007-10-02)
		Cristobalite exposure alone led to an increase in monocyte chemotactic protein (MCP)-1, macrophage inflammatory protein (MIP-2), and RANTES (regulated upon activation, normal T cell expressed and secreted) mRNA.
		The combination of cristobalite +TNF-[alpha] led to an additive increase in MCP-1 and MIP-2 whereas cristobalite + IFN-[gamma] or LPS had a synergistic effect.
		The results indicate that the cristobalite-induced chemokine response in the lung epithelium is mediated in part by TNF- [alpha] and can be enhanced by macrophage and lymphocyte derived inflammatory mediators in a additive and synergistic fashion.
	www.uth.tmc.edu /apstracts/1998/lung/September/190L.html (306 words)

	Re: AA Crash Site Assistance Requested - Stanford
		Cristobalite is a always a pseudomorph after Beta Cristobalite, which transformation could not have occurred in the open, surface environment after a UFO crash.
		Ed, you might cash-in nicely on that pretty rock at some mineral show (offered as Cristobalite, beside a copy of any XRD analysis statement you might have), but as to science, Cristobalite and the other material accompanying it are no evidence, whatsoever, of a UFO crash.
		List readers, Cristobalite may be there if Ed's report is accurate, but it is fairly rare only because most Cristobalite is deep underground in volcanic regions.
	www.virtuallystrange.net /ufo/updates/2003/oct/m03-003.shtml (531 words)

	Nomenclature of silica
		Beta Cristobalite, also called High Cristobalite, is the high temperature product, forming in the "gc" range in cooling.
		Alpha Cristobalite, or Low Cristobalite, at 200-275°, providing cooling through the "ct" and "tq" ranges has been too rapid for recrystallization.
		Rarely, perhaps, are included tridymites or cristobalites, but their occurrence is rare, and specimens are not often found under other than their type names.
	www.minsocam.org /MSA/collectors_corner/arc/silicanom.htm (2750 words)

	Research programs : Minerals at high pressure and temperature (Site not responding. Last check: 2007-10-02)
		The cell parameters of quartz and cristobalite have been measured up to their melting points from X-ray diffraction experiments with synchrotron radiation.
		For almandine, decomposition begins at about 1300 K and is triggered by oxidation of iron, with the formation of hematite, sillimanite and quartz or cristobalite.
		This approach also demonstrates the influence of the alpha-beta transition on structural disorder and assigns the unit-cell contraction observed at high temperature to the decrease of the first Si-Si distance due to the large thermal motion of oxygen atoms which cause the neighboring tetrahedra to come closer Co each other.
	www.ipgp.jussieu.fr /anglais/rub-recherche/eq09geomateriaux-pression/rech2ni-detail05.html (1766 words)

	Quartz Group
		Both high temperature minerals, cristobalite and tridymite, have both a lower density and index of refraction than quartz.
		The differences between cristobalite and beta cristobalite as well as the differences between tridymite and beta tridymite are shown in table below.
		Interestingly the structure of beta cristobalite is analogous to the structure of diamond.
	mineral.galleries.com /minerals/silicate/quartz.htm (1142 words)

	Silica-induced chemokine expression in alveolar type II cells is mediated by TNF-alpha -- Barrett et al. 275 (6): 1110 ...
		Cristobalite, a form of crystalline silica (a gift from Dr. D.
		Cristobalite caused a dose- and time-dependent increase in LDH release
		Effect of cristobalite exposure on epithelial cell chemokine expression.
	ajplung.physiology.org /cgi/content/full/275/6/L1110 (4609 words)

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