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Journal Article

Thermal analysis of quartz and its use in calibration in thermal analysis studies

01 Jun 1948-American Mineralogist (GeoScienceWorld)-Vol. 33, pp 337-345
About: This article is published in American Mineralogist.The article was published on 1948-06-01 and is currently open access. It has received 13 citations till now. The article focuses on the topics: Calibration (statistics) & Thermal analysis.
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Book ChapterDOI
18 Oct 1989
TL;DR: The structural order defines the individual polymorph and results in unique physical and chemical properties which are briefly summarized below as discussed by the authors, where the definitions of the disordered silica polymorphs as proposed by J.B. Jones and Segnit appear to be more widely adopted and will be utilized, where possible, throughout this chapter.
Abstract: In nature, silica (Si02) occurs as seven distinct polymorphs: quartz, cristobalite, tridymite, coesite, stishovite, lechatelierite (silica glass), and opal; the latter two are amorphous. Of these minerals, quartz is most abundant in soil environments, while disordered cristobalite commonly occurs in soils. Tridymite is rare in soils and is usually associated with siliceous volcanic rocks. Coesite, stishovite, and lechatelierite are rare polymorphic forms produced at high pressures, but found under atmospheric temperature and pressure at sites of meteor impact. Opal is a hydrated "amorphous" silica that comprises the bulk of diatomaceous rocks of biogenic origin and silica of inorganic origin (Frondel, 1962; Deer et aI., 1978). This chapter emphasizes quartz and the disordered polymorphs of silica. The disordered polymorphs have been referred to by a number of conflicting and sometimes ambiguous names, often resulting in confusion. The definitions of the disordered silica polymorphs as proposed by J.B. Jones and Segnit (1971) appear to be more widely adopted and will be utilized, where possible, throughout this chapter. Each of these distinct and unique polymorphs of silica expresses a definite degree of structural order. The structural order defines the individual polymorph and results in unique physical and chemical properties which are briefly summarized below.

228 citations

Journal ArticleDOI
TL;DR: In this article, the authors compared the reliability of two clay mineral identification methods: combined differential thermal analysis and thermogravimetry (DTA-TG ) and the methylene blue adsorption test (MBAT ).

42 citations

Journal ArticleDOI
TL;DR: Differential thermal analysis (DTA) has been used for many materials, but the major applications have been concerned with clay and carbonate minerals as mentioned in this paper, and the typical DTA curves for clay minerals the low-temperature endothermic loop associated with the loss of water.
Abstract: Differential thermal analysis (DTA) began soon after the development of the thermocouple. It has progressed through the systematic development of better equipment and the cataloguing of typical DTA curves for a variety of materials until good technique now requires control of the composition and pressure of the furnace atmosphere as well as consideration of the thermodynamics and kinetics of the reactions involved. Although differential thermal analyses have been made for many materials, the major applications have been concerned with clay and carbonate minerals. In DTA curves for clay minerals the low-temperature endothermic loop associated with the loss of water, and the high-temperature exothermic loop accompanying the formation of new compounds, are changed in shape, temperature, and intensity by the kind of exchange cations. The midtemperature-range endothermic loop has a temperature dependence on the partial pressure of water in the furnace atmosphere. For the anhydrous normal carbonates the dissociation temperature and its dependence on the partial pressvire of CO2 are in the decreasing order Ca, Mg, Mn, Fe, and Zn. The lower temperature loop of dolomite, the reaction for which must be preceded by an internal rearrangement, is independent of the pressure of CO2 but may be shifted to a lower temperature by prolonged fine grinding which accomplishes a similar rearrangement.

30 citations