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Tridymite

About: Tridymite is a research topic. Over the lifetime, 840 publications have been published within this topic receiving 14831 citations.


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Journal ArticleDOI
TL;DR: In this article, the primary fields of cristobalite, tridymite, Li2O·2SiO2, Li 2O·MgO·SiO 2, Li 2 O·Si O 2, MgSiO3, Mg2Si O 4, and Li2 O·NgO2-Mg2NiO4 were located for the system lithium metasilicate-forsterite-silica, and the positions of four invariant points and three composition triangles were established.
Abstract: The primary fields of cristobalite, tridymite, Li2O·2SiO2, Li2O·SiO2, MgSiO3, Mg2SiO4, and a new compound, Li2O·MgO·SiO2, have been located for the system lithium metasilicate-forsterite–silica. Most of the primary field for the compound Li2O·MgO·SiO2 lies below the join Li2O·SiO2-Mg2SiO4, but a small portion of it lies in the composition triangle Li2SiO3-Mg2SiO4-MgSiO3. The positions of four invariant points and three composition triangles have been established.

22 citations

Journal ArticleDOI
TL;DR: In this paper, the authors derived energy versus Si-O-Si angle curves for pure germania models of cristobalite and discussed which framework types are possible for pure-silica and pure-germania based on a rigid tetrahedron model.
Abstract: Cristobalite is the only corner-sharing tetrahedral framework that can maintain perfectly regular SiO4 tetrahedra throughout the entire 180° range of Si–O–Si angles. It is, thus, the ideal system for a study of the energy dependence of the Si–O–Si angle in a crystalline framework. Using the VASP first principles density functional code, we have derived energy versus Si–O–Si angle curves for pure silica and versus Ge–O–Ge angles for pure germania models of cristobalite. In addition, the frameworks of quartz, tridymite, and the zeolites sodalite (SOD) and metavariscite (BCT) were studied. The range of angles with low energies is larger for silica, though the lowest-energy Ge–O–Ge angle is always lower than the corresponding lowest-energy Si–O–Si angle in the same framework type. We discuss which framework types are possible for pure-silica and pure-germania based on a rigid tetrahedron model.

22 citations

Journal ArticleDOI
15 Jan 1973-Nature
TL;DR: In this article, it was shown that both the synthetic microspheres and the deep sea micro-spheres may be composed of hybrid crystals of interlayered cristobalite and tridymite.
Abstract: Weaver and Wise1 have shown that deep sea cristobalitic “cherts”, presumed to be precursors of quartz cherts, are composed in large part of blade-shaped crystals comprising microspheres 3–10 µm in diameter; these crystals were thought to be cristobalite. I have synthesized similar microspheres by hydrothermal crystallization of silica gel; however, the crystal habit of this synthetic material resembles that of tridymite rather than cristobalite. I suggest that both the synthetic microspheres and the deep sea microspheres may be composed of hybrid crystals of interlayered cristobalite and tridymite.

22 citations

Journal ArticleDOI
TL;DR: Mason Gully, the second meteorite recovered using the Desert Fireball Network (DFN), is characterized using petrography, mineralogy, oxygen isotopes, bulk chemistry, and physical properties as mentioned in this paper.
Abstract: Mason Gully, the second meteorite recovered using the Desert Fireball Network (DFN), is characterized using petrography, mineralogy, oxygen isotopes, bulk chemistry, and physical properties. Geochemical data are consistent with its classification as an H5 ordinary chondrite. Several properties distinguish it from most other H chondrites. Its 10.7% porosity is predominantly macroscopic, present as intergranular void spaces rather than microscopic cracks. Modal mineralogy (determined via PS-XRD, element mapping via energy dispersive spectroscopy [EDS], and X-ray tomography [for sulfide, metal, and porosity volume fractions]) consistently gives an unusually low olivine/orthopyroxene ratio (0.67−0.76 for Mason Gully versus ~1.3 for typical H5 ordinary chondrites). Widespread “silicate darkening” is observed. In addition, it contains a bright green crystalline object at the surface of the recovered stone (diameter ≈ 1.5 mm), which has a tridymite core with minor α-quartz and a rim of both low- and high-Ca pyroxene. The mineralogy allows the calculation of the temperatures and ƒ(O2) characterizing thermal metamorphism on the parent body using both the two-pyroxene and the olivine-chromite geo-oxybarometers. These indicate that MG experienced a peak metamorphic temperature of ~900 °C and had a similar ƒ(O2) to Kernouve (H6) that was buffered by the reaction between olivine, metal, and pyroxene. There is no evidence for shock, consistent with the observed porosity structure. Thus, while Mason Gully has some unique properties, its geochemistry indicates a similar thermal evolution to other H chondrites. The presence of tridymite, while rare, is seen in other OCs and likely exogenous; however, the green object itself may result from metamorphism.

22 citations

Journal ArticleDOI
TL;DR: In this paper, the extent of liquid immiscibility in the system K2O-FeO-Al2O3-SiO2 in the vicinity of the plane fayalite-leucite-silica has been experimentally determined.
Abstract: The extent of the low temperature field of liquid immiscibility in the system K2O-FeO-Al2O3-SiO2 in the vicinity of the plane fayalite-leucite-silica has been experimentally determined. The combination of direct oxygen buffering with the use of a zirconia probe to monitor oxygen activity has allowed minimisation of K2O-loss in the experiments while oxygen activity appropriate to the iron-wustite buffer has been maintained. The four-phase assemblage, fayalite+tridymite+FeO-rich liquid+SiO2-rich liquid, isobaric univariant in the quaternary system, occurs over a very small temperature range at about 1,163° C on the iron-wustite buffer. Both liquids appear to be in a coprecipitation relationship with tridymite and fayalite although the relationships between the two liquids are more complicated. The distribution of elements between the two coexisting liquids shows an interesting concordance when plotted in a new way. The results make sense in terms of current knowledge about silicate liquid structure, including the (familiar) observation that K/Al in the SiO2-rich liquid is always greater than in the coexisting FeO-rich liquid.

21 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202315
202231
202125
202027
201920
201826