Tridymite

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

Infrared Spectra for Mineral Identification

Abstract: The use of solid infrared spectroscopy is shown to greatly augment the use of x-ray diffraction spectra for mineral identification. Moreover, the method alone is helpful in analyzing dust samples of interest in the occupational health field. Some of the literature in this area is reviewed. Qualitative infrared spectra for mineral identification are presented for actinolite, amosite, anthophyllite, crocidolite, tremolite, gedrite, quartz, cristobalite, tridymite, kaolin, vermiculite, corundum, hematite, magnetite, muscovite, pyrophyllite, talc, antigorite, serpentine, and chrysotile.

EQUILIBRIUM RELATIONSHIPS ON THE LIQUIDUS SURFACE IN PART OF THE MnO-Al2O3-SiO2 SYSTEM*

Abstract: The minerals found to have a stability range on the liquidus surface in the system MnO-Al2O3-SiO2 are cristobalite and tridymite, SiO2; mullite, 3Al2O3. 2SiO2; corundum, Al2O3; rhodonite, MnO.SiO2; tephroite, 2MnO.SiO2; galaxite, MnO.Al2O3; spessartite, 3MnO.Al2O3.3SiO2; and a new compound, 2MnO.2Al2O3.5SiO2. The quintuple points and boundary lines found in that part of the MnO.Al2O3.SiO2 system bounded by the systems 3MnO.Al2O3.3SiO2-SiO2, 3MnO.Al2O3.3SiO2-Al2O3, and Al2O3-SiO2have been determined. Quintuple points and boundary lines involving the area inclosed by the systems 2MnO . SiO2-3MnO . Al2O3 . 3SiO2, 3MnO . Al2O3 . 3SiO2-SiO2, and 2MnO.-SiO2-SiO2 are indicated. Isotherms and isofracts (lines of equal refractive index) are given for the portion of the system investigated. X-ray data show that crystals of the compound 3MnO.Al2O3.3SiO2 have the same structure as the garnet mineral spessartite (manganese garnet). The compound 2MnO. 2Al2O3 . 5SiO2, which is shown by X-ray data to have a basic structure similar to cordierite, 2MgO.2Al2O3.5SiO2, seldom crystallizes from the glass, but a third substance which has a high extinction angle crystallizes readily from the reheated glass. These high extinction angle crystals are replaced by 2MnO .2Al2O3.5SiO2 when a proper heating cycle is employed, and they are not found again until the product is melted and crystallization is repeated.

X-ray powder diffraction patterns and phase relationship of tridymite modifications

Abstract: Calculated and observed X-ray powder patterns of three ambient temperature modifications of tridymite: L1-T O (=ordered low-tridymite MC), L2-T D (=disordered low-tridymite PO 5/10 ) and L3-T o (=ordered low-tridymite MX-1) are reported. Deviations in the diffractograms due to texture effect, stacking disorder and intergrowth of different modifications which complicate identification and indexing are discussed. Changes of unit cell dimensions due to thermal expansion and phase transitions were measured from room temperature to about 700 o C. Near 160 o C all ordered and slightly disordered tridymite polymorphs transform to monoclinic high tridymite H3-T (OS) with non-integral modulation, at about 210 o C to orthorhombic high tridymite H2-T (OC) and finally at about 400 o C to hexagonal high-tridymite H1-T (HP)

Temperature Inversions of Anhydrous Gallium Orthophosphate

Abstract: Crystalline GaPO4 was prepared in a hydrothermal bomb at 200° to 300°C. It was found to be isostructural with the berlinite form of AlP04. Thermal analysis and high-temperature X-ray techniques were utilized to show that the analogy extends to some of the polymorphic forms of AlPO4 as well. Three forms of GaPO4, corresponding to the berlinite, high-cristobalite, and low-cristobalite forms of the A1PO4 system, were observed. No evidence was found to indicate the existence of a tridymite form.