. Annals of the New York Academy of Sciences. Science. 254 IRVING. be caused by the parallel arrangement of a mass of feldspar in- clusions, most of them orthoclase, but one or two of them albite. (Fig. 13.). Fig. 13. Zonally arranged inclusions in quartz phenocryst from quartz-aegirite- porphyry ; Annie creek type. 5. Sunset Mine Type. This rock is perhaps the most interesting of the series. Megascopic Appearance.—It is a porphyritic rock, dark colored in the fresher specimens, and shows large phenocrysts of orthoclase and quartz. The quartz crystals are large, often y% inch in diameter, and
. Annals of the New York Academy of Sciences. Science. 254 IRVING. be caused by the parallel arrangement of a mass of feldspar in- clusions, most of them orthoclase, but one or two of them albite. (Fig. 13.). Fig. 13. Zonally arranged inclusions in quartz phenocryst from quartz-aegirite- porphyry ; Annie creek type. 5. Sunset Mine Type. This rock is perhaps the most interesting of the series. Megascopic Appearance.—It is a porphyritic rock, dark colored in the fresher specimens, and shows large phenocrysts of orthoclase and quartz. The quartz crystals are large, often y% inch in diameter, and much rounded by resorption, and are in many cases elongated; sometimes so much so, that the length will be fifteen times the breadth. When drawn out in this manner, the phenocrysts all lie with their longer axes in the same direction. Microscopic CJiaractcrs.—The feldspars are orthoclase, fre- quently fractured and much resorbed. The cores of the crys- tals are quite clear but the borders contain inclusions, and seem to have been formed later than the main body of the crys- Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original New York Academy of Sciences. New York, New York Academy of Sciences
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1877
