Authors:Ágnes Skultéti, Tivadar M. Tóth, István János Kovács, Edit Király, and Judit Sándorné Kovács
areas ( Szederkényi 1977 ). In the dislocation zone, intensively mylonitized metamorphic rocks of various lithologies crop out. Gneiss, quartz phyllite, crystalline limestone, serpentinite, and amphibolite compose the Mecsekalja Zone and
The quartz-cristobalite transformation in heated natural chert (flint) rock composed of micro- and ŗypto-quartz was investigated
in the temperature interval of 1000–1300°C by micro-Raman spectroscopy, FT-IR spectroscopy, X-ray diffraction and Scanning
Electron Microscopy. A small amount of crystobalite was first observed in the chert after heating at 1000°C for 1 h and the
transformation was almost completed after heating at 1300°C for 24 h. On the other hand, cristobalite was not detected in
well-crystallized pure quartz after heating under the same conditions. The transformation occurs as a solid state nucleation
and crystal growth of cristobalite replacing quartz at high-temperatures. The chert rock is naturally rich in crystal defects
and boundaries which serve as nucleation sites and enable an earlier quartz-cristobalite transformation.
In this work two aluminic pozzolans (metakaolins) and a non-pozzolan were added to two Portland cements with very different
mineral composition, to determine the effect on the rate of heat release and the mechanisms involved. The main analytical
techniques deployed were: conduction calorimetry, pozzolanicity and XRD.
The results showed that the two metakaolins induced stimulation of the hydration reactions due to the generation of pozzolanic
activity at very early stage, because of their reactive alumina, Al2O3r− contents, mainly. Such stimulation was found to be more specific than generic for more intense C3A hydration than C3S, at least at very early on into the reaction, and more so when 7.0% SO3 was added, and for this reason, such stimulation is described as ‘indirect’ to differentiate it from the ‘direct’ variety.
As a result of both stimulations, the heat of hydration released is easy to assimilate to a Synergistic Calorific Effect.
The paper reviews studies on possible applications of the high-low quartz inversion in petrology. Since the first suggestions of Fenner and Tuttle, nearly fifty papers have dealt with the subject, including ten by the present authors. The detailed discussion of the preparative and instrumental factors which may influence the quartz inversion behaviour reveals that the DTA (DSC) runs have to be made under highly standardized conditions to permit measurement of the ‘material inherent factors’ (mainly crystal physical factors) which cause variations in shape and temperatures. The most striking variations in shape and temperatures of the inversion effect (e.g. including temperatures more than 70°C lower than the ‘textbook value’ of 573°C for the quartz inversion) are observed for microcrystalline quartz crystals. The literature and the authors' own investigation demonstrate that the most interesting field of application of the method is that of authigenic quartz formation in sediments and soils. The characterization of metamorphic quartz is more complicated. Four fields of study are chosen to demonstrate the possible application of the quartz inversion characterization for petrogenetic interpretations: (1) the differentiation between authigenic and inherited quartz crystals in sediments, (2) the characterization of the contact-metamorphic aureoles around granites, (3) special regional-metamorphic terrains and (4) (from a few so far unpublished studies) the differentiation between sedimentary and soil silcretes.
Authors:Gergely Dabi, Ferenc Tóth, and Félix Schubert
Fluid inclusion planes (FIPs) are fossilized mode I microcracks, formed perpendicular to the σ 3 direction in minerals, which can be mechanically considered isotropic during brittle deformation, e.g., in quartz
Authors:I. Kuleff, R. Djingova, K. Kostadinov, and D. Todorovsky
A scheme for INAA of 32 elements (As, Au, Ba, Br, Ca, Cd, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, Ir, K, La, Lu, Mn, Na, Nd, Rb, Sb,
Sc, Sm, Ta, Tb, Th, U, W. Yb, Zn) in quartz glass is proposed. The accuracy of the procedure is evaluated by the analysis
of two NBS standard reference materials (SRM-1571 and SRM-1632-a). The method is convenient for routine work. The method was
used for the determination of impurities in laboratory quartz glass.
Authors:Katharina Pock, F. Steger, and T. Schönfeld
The thorium content of quartz glass tubing was found to vary greatly from very low values (<5 ng Th/g) to about 300 ng Th/g. When trace amounts of thorium are to be determined by activation analysis, e.g. in excreta, thorium content of quartz glass irradiation vials has to be taken into consideration. Analysis of fecal ash samples from persons living in the Vienna area who were not occupationally exposed to thorium containing dust, gave thorium excretion rates in feces of 0.5 to 8 g per day. For occupationally exposed persons some of the values were much higher, up to 70 g per day.
The bacground to the supposed development of the ‘Beilby layer’ on fine-grinding quartz is briefly reviewed. It is shown,
using single crucible thermal analysis and sub-milligram DTA, that grinding quartz can cause a dispersion of the α-β inversion
over a temperature range of several degrees; this is a crystallographic effect rather than an impurity effect. The sub-milligram
DTA apparatus used is described and some thermal effects, such as impurity zoning, are illustrated.