Bulletin Volume 9, PT. 1

Bulletin Volume 9, PT. 1

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 edition. Excerpt: ...no tendency to porphyritic structure whatsoever. On the same road, five miles slightly east of south from Greensboro, at Veazy's store, are outcrops of a coarsebut close-grained granite, the feldspars of which have a decidedly pinkish color. The rock carries but little mica. Another outcrop of the same granite is seen on the north side of a stream near the store. About four miles southeast from Greensboro, along the same road and on the north side of Beaver Dam creek, is an outcrop of practically the same granite; but the quartz in it is of a smoky variety, decidedly dark in color. But little mica is present, and the feldspar is flesh-colored. The outcrops of this rock are more or less continuous along the wagon-road, to within several miles a little east of south of Greensboro. After leaving the main outcrop of the porphyritic granite and travelling towards Greensboro, the outcrops are invariably of the boulder type, usually of extraordinary dimensions.' 1 See Plate XVII, Fig. 1. Owing to a lack of fresh granite exposures, from the extreme depth of covering of the residual rock decay, the exact relationship between the two granite facies could not be worked out in the field. The nearest exposures of the porphyritic and non-porphyritic, or even-granular, granite to each other showed no appreciable gradation from one to the other. While the necessary exposures are lacking, there can scarcely be any doubt, as to the two facies representing the same granite-mass, with the central portion porphyritically developed, grading peripherally into an even-grained granite, of the same mineral and chemical composition. As is shown below, the feldspar phenocrysts carry inclusions of the groundmass minerals, which proves that the porphyritic mineral, ...show more

Product details

  • Paperback | 150 pages
  • 189 x 246 x 8mm | 281g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236863887
  • 9781236863881