Petrographic examination

Year Two Field excursion to Wolf and Darwin Islands (24 days total 6 days on each island). Petrographic examination of samples at Lawrence University, initial analysis of trace elements by ICP-MS at Lawrence University (up to 100 samples). 

A proper understanding of the nature and behavior of resinite at all levels of rank will require considerable further effort. Petrographic examination of coals will no doubt yield additional data, but a more profitable line of attack would seem to lie in studying fresh and laboratory treated samples by a proper combination of microscopical and chemical analytical techniques. 

A preliminary examination of coal materials associated with igneous intrusions from two general areas in Colorado has been completed. A study of the field relationships, petrographic examination, chemical analyses, and reflectance studies has been conducted. Results can be summarized as follows ... 

Oxidized coal coal whose properties have been modified fundamentally as a result of chemisorptions of oxygen in the air or oxygen dissolved in ground-water. Chemisorption is a surface phenomenon rarely detectable by chemical analysis but usually detectable by petrographic examination. It reduces the affinity of coal surfaces for oil and seriously impairs coking, caking, and agglutinating properties. 

If quartz is analyzed by X-ray diffraction and the presence of an interfering peak is suspected, it may be possible to cross check the X-ray diffraction by petrographic examination of particles picked from the sample membrane. Quartz reflects light in a characteristic way also. The parlodian film which may be used in X-ray diffraction tends to interfere in petrographic examination. 

The high calcium content in the majolica found in Mexico City— 21.4% calculated as pure calcium carbonate compared with 5.9% in sherds of Teotihuacan—suggests that a calcium compound such as calcium or calcium magnesium carbonate may have been added to the majolica either as a temper or through deposition during burial. Petrographic examination of cross sections of representative Mexico City majolica sherds show heavy deposits of birefringent material with structures... 

We have been able to distinguish two distinctive groups of pottery among the majolica sherds excavated from Spanish sites in the New World. These distinctions are based on the examination and analysis of the paste portions of the sherds and have involved the combined use of neutron activation analysis, x-ray diflFraction analysis, and petrographic examination. Preliminary investigations of the relationships of each of these two groups of sherds to sherds of known origin have also been undertaken. There is evidence to support a Spanish source for the sherds from sites in the Dominican Republic and Venezuela and a Mexican source for the sherds excavated in Mexico City. 

We have been able to compare our samples to a small group of majolica sherds from Spain and to a reasonably large group of Precolumbian sherds from Teotihuacan. The majolica sherds from Caribbean sites agree in composition with the Spanish specimens, and those from sites in Mexico City have compositions sufBciently similar to the sherds from Teotihuacan, considering the secondary deposits of carbonates of calcium which are in the majolica sherds and not in the Precolumbian sherds. The presence of these deposits of carbonates of calcium in the majolica and their absence in the Precolumbian sherds was determined by petrographic examination and x-ray diflFraction as well as by elemental analysis. 

Furukawa et al. (2) measured C (15-370 K) using a sample prepared by stoichiometric proportions of LIF and AlFg in graphite. X-ray diffraction and petrographic examination of separate portions of the sample indicated a single phase identified as 0-LigAlFg. The authors tabulated values of C and S based on their data and the extrapolation S (15 K) = 0.042 cal K" mol". These values are adopted. 

On the surfaces of the silica brick utilized in the side walls, Insley observed an incrustation with a white, coral-like appearance. This frost was easily broken away from the surface consequently, very little evidence of corrosion of the silica brick was noticed. A petrographic examination of the frost revealed very small tridymite crystals in the part of the brick next to the frost. The contact material between the brick and the incrustation had a vitreous appearance composed of glass and large tridymite crystals. Further within the incrustation, the crystals were larger, but the quantity of glass was smaller. 

Petrographic examination under the microscope can provide Identification of the material, and can be complemented with techniques such as x-ray diffraction (XRD) to Identify crystalline minerals. The quantitative measure of the relative amounts of the minerals Is a somewhat controversial subject due to some of the limitations of the techniques. However the comparison of the results from a number of laboratories has led to the conclusion that no one XRD method Is superior to all others. Repeated attempts to compare results between different laboratories has led to the consensus that the technique Is seml-quantItative. 

G.C. Kennedy, suggesting that the quadruple point (gypsum—anhydrite— bassanite—H2O) is near 600 MPa (6 kbar) and 130°C, with the bassanite field widening in temperature at higher pressures. Zen (1965) estimated from thermochemical calculations and chemographic analysis that the quadruple point should be near 900 MPa (9 kbar) and 170°C. Solubility and phase-transformation experiments (Zen, 1965 Kinsman, 1974) indicate that bassanite is metastable at 0.101 MPa (1 atm.) and temperatures of 25—70°C. The conclusion of Goodman (1957) from petrographic examination that... 

The shock waves produced by meteorite impacts give rise not only to the obvious craters seen on planets and their satellites but also to subtle effects seen only with chemical and petrographic examination of the shocked material. Shock waves in the interplanetary and interstellar medium play an important role in the formation of stars and planets, including the Solar System. They also produce important chemical effects in interstellar clouds of dust and gas—including the production of rather complex organic molecules. 

EPM analysis for organic sulfur content can be performed easily on -20 to -100 mesh coal samples. Samples need only be mounted in epoxy and polished similar to how coal samples are commonly prepared for petrographic examination. 15 areas within non-contiguous vitrinite grains are analyzed with the EPM. Without the need to produce a photomosaic, the organic sulfur content of vitrinite, and therefore of a coal, may be determined in less than 10 minutes. 

ASTM C856-95el. Standard Practice for Petrographic Examination of Hardened Concrete. American Society of Testing and Materials, West Conshohocken, PA. 

Ahmed, W.U., "New Equipment Methods for Preparing Concrete Concrete Making Materials for Petrographic Examination," Proceedings of the 19th International Conference on Cement Microscopy, International Cement Microscopy Association, Cincinnati, Ohio, 1997, pp. 130-139. 

Another factor that must be taken into acconnt in determining coal quality is the degree of coal oxidation. Oxidation may affect both the organic and inorganic components and may lead to deterioration of the coal properties. Another possible conseqnence of coal oxidation is the spontaneous combustion (Misra and Singh, 1994 Beamish et al., 2001 Lyman and Volkmer, 2001 Beamish, 2005). The propensity to oxidation is mainly determined by the coal s rank in conjunction, perhaps, with the maceral and mineral (e.g., pyrite) content. Low-rank coals are particularly prone to spontaneous combustion. Other factors, such as the access of air to coal stockpiles, may need to be controlled in order to reduce the risk of spontaneous combustion. Petrographic examination may help to identify coals that have become oxidized. 

This standard specifies basic procedures for the petrographic examination of aggregates... 

Hammersley (1989) noted that the petrography of a rock mass, involving field inspection, can be of value in any assessment of its potential suitability for use as aggregate. In addition, petrographic examination can indicate the presence of deleterious materials and defects. 

ASTM C295. 2008. Standard Guide for Petrographic Examination of Aggregates for Concrete. Anntial Book of ASTM Standards (04.02) 9 pp. 

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