Microscopy and Cathodoluminescence Spectroscopy Characterization of Quartz Exhibiting Different Alkali–Silica Reaction Potential

Different quartz types from several localities in the Czech Republic and Sweden were examined by polarizing microscopy combined with cathodoluminescence (CL) microscopy, spectroscopy, and petrographic image analysis, and tested by use of an accelerated mortar bar test (following ASTM C1260). The highest alkali–silica reaction potential was indicated by very fine-grained chert, containing significant amounts of fine-grained to cryptocrystalline matrix. The chert exhibited a dark red CL emission band at ~640 nm with a low intensity. Fine-grained orthoquartzites, as well as fine-grained metamorphic vein quartz, separated from phyllite exhibited medium expansion values. The orthoquartzites showed various CL of quartz grains, from blue through violet, red, and brown. Two CL spectral bands at ~450 and ~630 nm, with various intensities, were detected. The quartz from phyllite displayed an inhomogeneous dark red CL with two CL spectral bands of low intensities at ~460 and ~640 nm. The massive coarse-grained pegmatite quartz from pegmatite was assessed to be nonreactive and displayed a typical short-lived blue CL (~480 nm). The higher reactivity of the fine-grained hydrothermal quartz may be connected with high concentrations of defect centers, and probably with amorphized micro-regions in the quartz, respectively; indicated by a yellow CL emission (~570 nm).

Quantitative Porosity Studies of Archaeological Ceramics by Petrographic Image Analysis

ABSTRACTPores in archaeological ceramics can form in a number of different ways, and reflect both deliberate choices and uncontrollable factors. Characterizing porosity by digital image analysis of thin sections holds a number of advantages as well as limitations. We present the results of experiments aimed at improving this method, focusing on high-resolution scans of entire thin sections. We examine the reproducibility of pore measurements by petrographic image analysis of ceramic thin sections using laboratory-prepared specimens of clay mixed with sand of known amount and size. We outline protocols for measuring Total Optical Porosity, using the Image-Pro Premier software package. We also briefly discuss use of pore size and pore shape (aspect ratio and roundness) in characterizing archaeological ceramics. While discerning reasons for observed amounts, sizes, and shapes of pores is an extremely complex problem, the quantitative analysis of ceramic porosity is one tool for characterizing a ware and comparing a product to others. The methods outlined here are applied to a case study comparing historic bricks from the Read House in New Castle, Delaware; the porosity studies indicate that different construction campaigns used bricks from different sources.

NMR Facies Definition for Permo-Triassic Kangan/Dalan Carbonate Formation by Use of Core/Log and Pore-Scale Measurements

Summary An integrated and quantitative approach is taken here to the Permo-Triassic Kangan/Dalan carbonate formation. We apply pore-network characterization to the problem of the classification of these complex carbonate gas-reservoir rocks. We start with the useful and convenient nuclear-magnetic-resonance (NMR) data on 28 samples to define NMR facies (NMRF). The NMRF grouping is performed with both the relaxivity constant (ρ2) and the specific-surface-volume (Sgv) data. Seven NMRF have been defined with a combination of core/log NMR data, petrographic image analysis, and mercury-injection examinations for two wells. The advantage of evaluation of the pore spaces rather than grain properties is to discover trends that are not apparent when one uses a conventional sedimentological facies definition. Lithology-independent NMRF exhibit properties that are associated with pore geometry. This should have special importance for the formation evaluation of carbonates.