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Topic: Metamictization

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Zircon

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	New mineral species for NY
		Investigation by transmitted light microscopy and X-ray diffraction showed that this chevkinite-(Ce) is completely metamictic and displays a decomposition texture.
		The metamictization process could explain the chemical variations and the large amount of water.
		In order to partially recover the structural pattern, we heated the mineral at 10000C for one hour and a half in a Ni crucible.
	www.nysam.org /new_ny.cfm (330 words)

	Metamictization
		Metamictization is a natural process resulting in the gradual and ultimately complete destruction of a mineral 's crystal lattice, leaving the mineral amorphous.
		Effects of metamictization are extensive: other than negating any birefringence previously present, the process also lowers a mineral's refractive index, hardness, and specific gravity.
		Curiously and inexplicably, the one attribute which metamictization does not alter is dispersion.
	www.brainyencyclopedia.com /encyclopedia/m/me/metamictization.html (272 words)

	Metamictization -- Facts, Info, and Encyclopedia article (Site not responding. Last check: )
		Further, metamictization diffuses the bands of a mineral's (The spectrum of electromagnetic radiation that has passed through a medium that absorbed radiation of certain wavelengths) absorption spectrum.
		An example of a metamict mineral is (A common mineral occurring in small crystals; chief source of zirconium; used as a refractory when opaque and as a gem when transparent) zircon.
		Metamict minerals can have their crystallinity and properties restored through prolonged (Hardening something by heat treatment) annealing.
	www.absoluteastronomy.com /encyclopedia/m/me/metamictization.htm (184 words)

	zircon "the key mineral"
		Although zircon is fairly resistant to normal chemical attack altered varieties, so called metamict zircons, are not uncommon, the mineral eventually becoming converted to an isotropic form with a lower density.
		Holland and Gottfried (1955) suggested that the observed effects are caused mainly by the displacement of atoms by recoil nuclei, and by the high temperatures produced in the path of the nuclear particles.
		The highest ratio is found in metamict varieties (0.06) while it increases from 0.015 for zircons in nepheline-syenites to 0.04 for those of granites (Rankama and Sahama, 1950).
	www.metu.edu.tr /~skoksal/geochemistry.htm (3930 words)

	Metamictization (Site not responding. Last check: )
		Metamictization is a natural process resulting in the gradual and ultimately complete destruction of a mineral 's crystallattice, leaving the mineral amorphous.
		Themineral's colour is also affected: metamict specimens are usually green or brown.
		Specimens falling between the two extremes are termed intermediate.Other minerals known to undergo metamictization include ekanite and titanite.
	www.therfcc.org /RFCC/metamictization-329380.html (224 words)

	ZircÃ´nia cÃºbica - WikipÃ©dia
		Although cubic, it was in the form of a polycrystalline ceramic : it was made use of as a refractory material, highly resistant to chemical and thermal (up to 2540Â°C) attack.
		Chudoba discovered naturally occurring cubic zirconia in the form of microscopic grains included in metamict zircon.
		Thought to be a byproduct of the metamictization process, the two scientists did not think the mineral important enough to formally name.
	pt.wikipedia.org /wiki/Zircônia_cúbica (1315 words)

	Lee A. Groat - Titanite and Malayaite
		The results were consistent with the Ewing model for metamict materials, an aperiodic random network structure; HRTEM images show patterns of random contrast consistent with the random network model (Fig.
		Heating a metamict sample at high temperature leads to an irreversible decrease of the absorption signal of the O-H stretching bands, together with a significant sharpening of the band profile.
		We believe that the recrystallization behaviour of a metamict sample is correlated with its dehydration.
	www.eos.ubc.ca /personal/groat/titanitemalayaite.htm (1301 words)

	Zircon article reviews
		It was found to be optically zoned in thin section, which is characteristic of metamictization resulting from zonation in U and Th concentrations.
		Metamictization of zircon has been the subject of extensive and very analytical research.
		More studies similar to this one will allow us to further understand the process of metamictization and how the process correlates with the storage of nuclear waste, as radioactive decay causes weakening of the holding structures and many potential problems.
	www.und.nodak.edu /instruct/mineral/geol318/webpage/zacher/zircon/reviews.html (1778 words)

	Mineralogical Record: IMA commission on new minerals and mineral names: Procedures and guidelines on mineral ...
		Some mineralogists are reluctant to accept amorphous substances as mineral species because of the difficulty of determining whether the substance is a true chemical compound or a mixture, and the impossibility of characterizing it completely; the term mineraloid is sometimes applied to such substances.
		The basis for accepting a naturally occurring amorphous phase as a mineral species could be a series of complete quantitative chemical analysis that are sufficient to reveal the homogeneous chemical composition of a substantial number of grains in the specimen, and physico-chemical data (normally spectroscopic) that prove the uniqueness of the phase.
		Metamict substances, if formed by geological processes, are accepted as mineral species if it can be established with reasonable certainty that the original substance (before metamictization) was a crystalline mineral of the same bulk composition.
	www.findarticles.com /p/articles/mi_qa3672/is_199905/ai_n8839539/pg_2 (1316 words)

	Acta Geologica Universitatis Comenianae Bratislava
		Metamictization and defective crystalline structure are results of radioactivity mainly by -particles.
		Metamictization is characteristic for few minerals as U and Th silicates and titanates, compound oxides of Ta, Nb and Ti (titaniumtantalumniobates), some REE silicates and zircon.
		The amorphous or microcrystalline form is not the result of metamictization but it is their original form.
	www.fns.uniba.sk /prifuk/casopisy/geol/1997mon/cwsu31.htm (750 words)

	[No title] (Site not responding. Last check: )
		The degree of metamictization was estimated by means of confocal laser-Raman spectroscopic measurements.
		Raman band broadening in well-ordered to moderately metamict zircons that have not experienced significant healing of the radiation damage since the time of their growth, shows a nearly linear dependence on the
		The dependence is proposed as a calibration line for examinig unknown zircons in order to consider complete or incomplete damage storage, which may contribute to the understanding of the low-T thermal history of their host rocks.
	www.uni-tuebingen.de /uni/emi/ag-markl/pages/wenzel/pages/abstracts/tw2001a.html (235 words)

	Abstracts (Site not responding. Last check: )
		R.B. Greegor, F.W. Lytle and R.C. Ewing (1990) Zr-site characterization in metamict and annealed zircon by x-ray absorption spectroscopy.
		R.C. Ewing (1990) Characterization of amorphization (metamictization) and annealing kinetics in crystalline silicates, complex oxides and phosphates.
		R.K. Eby, J. Janeczek, R.C. Ewing, B.C. Chakoumakos, T.S. Ercit, L.A. Groat, F.C. Hawthorne (1992) Metamictization* and alteration of vesuvianite.
	www.geo.lsa.umich.edu /relw/publications/abstracts.htm (8947 words)

	Metamictization - Result for Metamictization - Meaning of Metamictization - Definition of Metamictization - Dictionary ...
		Effects of metamictization are extensive: other than negating any birefringence previously present, the process also lowers a mineral's refractive index, Mohs hardness scale hardness, and specific gravity.
		Curiously and inexplicably, the one attribute which metamictization does not alter is dispersion (optics) dispersion.
		There you find a list of all editors and the possibility to edit the original text of the article Metamictization.
	www.mauspfeil.net /Metamictization.html (298 words)

	Earth Materials, Experimental Petrology (Site not responding. Last check: )
		Detrital zircons from the Rio Cachorrinho, a small mountain stream, the drainage of which lies entirely within the Tombador conglomerate, were dated by laser ablation ICP-MS.
		Detrital grains were used because the large clast size (>25 cm) of the conglomerate makes processing a representative sample of the conglomerate difficult, and because transport in the Rio Cachorrinho should preferentially destroy metamict zircons.
		Previous studies of zircons extracted from the Tombador formation have shown that metamictization is a serious problem among detrital zircons found in these conglomerates and quartzites.
	rses.anu.edu.au /pep/annualreports/annualreport2000/project10.html (472 words)

	Abstracts
		Crystals with very different features (e.g., clearness, presence of inclusions, elongation ratio, roundness, degree of metamictization) were identified.
		Due to the small size of the available samples, a statistically significant description of zircon populations was not possible, as less than 70 zircon crystals were extracted.
		Disregarding highly metamictic zircons, other populations were classified according to the scheme of Pupin (1980):
	www.geo.unipr.it /~meli/pubblicazioni/ve_simp2000.htm (779 words)

	Metamictization and chemical durability of detrital zircon -- Balan et al. 86 (9): 1025 -- American Mineralogist
		Metamictization and chemical durability of detrital zircon -- Balan et al.
		We have investigated the effect that metamictization has on
		Low-temperature hydrothermal alteration of natural metamict zircons from the Eastern Desert, Egypt
	ammin.geoscienceworld.org /cgi/content/abstract/86/9/1025 (493 words)

	INCT Home Page (Site not responding. Last check: )
		Fe Mössbauer spectroscopy, X-ray diffraction (XRD) and gamma-ray spectroscopy studies of partially metamict gadolinites from Szklarska Porêba and Zimnik (Lower Silesia, Poland), a fully metamict gadolinite sample from Ytterby (Sweden) and a crystalline sample obtained after annealing of a fragment of the sample from Ytterby at 1373 K in an argon atmosphere.
		Changes of the amplitudes ratio of high energy to low energy absorption peaks from Fe quadrupole doublets are strictly correlated with calculated absorbed alpha-dose and the metamictization stages of the gadolinite specimens.
		In this respect, one of the samples is in conflict with the estimated radiation dose based on age and radionuclide concentrations.
	www.ichtj.waw.pl /ichtj/nukleon/back/abstract/vol48_2003/v48s1p041.htm (158 words)

	Uranium in mineral sands: measurement and uses
		As a word of caution, some zircons contain so much uranium (or are so old) that the fission track radiation damage is so severe that they cannot be etched without dissolving the entire grain.
		This is a part of the process of metamictization.
		In such cases, a particular provenance age may not be revealed even though it makes up a high proportion of the zircons present.
	www.geotrack.com.au /minsand.htm (1572 words)

	Invited Papers and Presentations (Site not responding. Last check: )
		"The Metamict State": Seminar at the Department of Earth and Space Sciences, University of California, Los Angeles, May 4, 1989.
		"Metamictization": at the Department of Mineralogy, Crystallography, and Geochemistry, Charles University, Prague, Czechoslovakia, October 14, 1989.
		"Structure of the Metamict State": at the Mineralogical Institute, Tokyo University, Tokyo, April 13, 1990.
	www-ners.engin.umich.edu /relw/publications/presentations.htm (1985 words)

	662
		metamictization, strongly modifies the bulk thermodynamic properties of zircon.
		Because surface properties are known to control the silicate weathering rates and may be different from bulk properties, a detailed study of the surface of zircon has been undertaken inorder to better understand the resistance of zircon to dissolution.
		In the case of variably metamict zircon, the metamictization degree can be determined using Raman spectroscopy and is shown to partly control the surface morphology of zircon in tropical soils.
	www.the-conference.com /JConfAbs/4/662.html (7536 words)

	Mineralogist.ru >> Science (Site not responding. Last check: )
		In spite of the large number of studies on steenstrupine, due to the complexity of the mineral and the frequent metamictization and alteration (its composition may differ from one specimen to the other and even inside sectors of the same crystal or grain), the formulae proposed till the eighties are not reliable.
		A similar situation occurs, for example, in the case of zirconosilicates of eudialyte group, as shown by the recent description of various new members and the relevant nomenclature problems.
		The case of "steenstrupines" is still more complicated, because their frequent metamictization is a serious obstacle to deep structure investigations.
	www.mineralogist.ru /science/rmi-4-01.shtml (2072 words)

	Journal Articles (Site not responding. Last check: )
		Rodney C. Ewing (1976) Metamict mineral alteration: An implication for radioactive waste disposal.
		Headley and R. Ewing (1986) TEM study of the microstructure of metamict minerals.
		E.K.H. Salje, J. Chrosch and R.C. Ewing (1999) Is “Metamictization” of zircon a phase transition?
	www.geo.lsa.umich.edu /relw/publications/journal.htm (4325 words)

	Caffe
		Conventional TIMS analyses of these columbite-tantalite crystals produces scattered data and reverse discordance even after HF leaching of the grains prior to dissolution, possibly reflecting the incomplete removal of the open-system metamict segments during sample preparation.
		This discordance represents an analytical artefact originating from an inappropriate correction of elemental fractionation between U and Pb during ablation and extraction that itself may take its origin in the contrasting metamictization of the dated columbite and the monazite standard used.
		Best age estimates of columbite from pegmatites in the Superior Province are; 2670 ± 5 Ma for the Pakeagama Lake pegmatite, 2644 ± 7 Ma for the Separation Rapids group, and 2665 ± 8 Ma for the Mavis Lake group.
	www.gfz-potsdam.de /pb4/pg2/people/romer/ROMER-46.htm (304 words)

	Xenotime - Enpsychlopedia (Site not responding. Last check: )
		Xenotime is dichroic with pink, yellow, or yellowish brown seen in the extraordinary ray, and brownish yellow, grayish brown or greenish brown seen in the ordinary ray.
		While xenotime may contain significant amounts of thorium or uranium, the mineral does not undergo metamictization like sphene or zircon would.
		Occurring as a minor accessory mineral, xenotime is found in pegmatites and other igneous rocks, as well as gneisses rich in mica and quartz.
	www.grohol.com /psypsych/Xenotime (648 words)

	New
		Although cubic, it was in the form of a polycrystalline ceramic: it was made use of as a refractory material, highly resistant to chemical and thermal (up to 2540°C) attack.
		Seven years later, German mineralogists M. Stackelberg and K. Chudoba discovered naturally occurring cubic zirconia in the form of microscopic grains included in metamict zircon.
		Thought to be a byproduct of the metamictization process, the two scientists did not think the mineral important enough to formally name.
	www.jewelersstudio.com /cz_info.htm (1570 words)

	metamictization of zircon (Site not responding. Last check: )
		The degree of metamictization of the zircon, as indicated by unit-cell parameters, increases systematically with U-Th content up to the point of total metamictization.
		The appearance of IR spectra also varies as a function of metamictization; band widths increase and intensities decrease with increasing U-Th contents.
		Hydrous components enter the structure only after total metamictization, but the amounts are not correlated with U-Th content.
	minerals.gps.caltech.edu /manuscripts/1991/zircon_hydrous (191 words)

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