Annual report of the United States Geological Survey to the Secretary of the Interior . PLATE XLVII. 1 PLATE XLVII. A. Poikilitic gabbro, No. 985 S. N., showing the broken and corroded anorthites inclosed in later brown hornblende. The feldspars lie at all angles in thehornblende plate, which has the same optical orientation throughout. Thisis an illustration of the typical poikilitic structure as characterized by H. Williams. With the analyzer, X 20. B. Gabbro, No. 535 S. N., showing the gabbro or typical granular structure in which both the main constituents, pyroxene and plagioclase
Annual report of the United States Geological Survey to the Secretary of the Interior . PLATE XLVII. 1 PLATE XLVII. A. Poikilitic gabbro, No. 985 S. N., showing the broken and corroded anorthites inclosed in later brown hornblende. The feldspars lie at all angles in thehornblende plate, which has the same optical orientation throughout. Thisis an illustration of the typical poikilitic structure as characterized by H. Williams. With the analyzer, X 20. B. Gabbro, No. 535 S. N., showing the gabbro or typical granular structure in which both the main constituents, pyroxene and plagioclase, appear to have crystal-lized at about the same time, the anhedrons of each mutually interfering, sothat none of the grains attained their proper crystalline forms. With the ana-lyzer, X 40. C— plagioclase; A = hornblende; P = augite; H = hypersthene;F = iron GEOLOGICAL SURVEY SEVENTEENTH ANNUAL REPORT PART I PL. XLVII
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