Annual report of the United States Geological Survey to the Secretary of the Interior . PLATE XLIII 17 GEOL, PT I 48 753 PLATE XLIII. A. Soda-8yenite-porphyry, No. 46 Tuolumne, showing the microcrystalline ground- mass of albite grains in which are embedded phenocrysts of plagioclase. Withthe analyzer, X 50. B. A view of another portion of the same section as the previous, showing radiating brushes of delicate blue hornblende needles. Without the analyzer, X PLATE XLIV. PLATE XLIV. A. Diorite-porphyry, No. 298 S. N., showing the idiomorphic tendency of the plagio- clase and hornblende.
Annual report of the United States Geological Survey to the Secretary of the Interior . PLATE XLIII 17 GEOL, PT I 48 753 PLATE XLIII. A. Soda-8yenite-porphyry, No. 46 Tuolumne, showing the microcrystalline ground- mass of albite grains in which are embedded phenocrysts of plagioclase. Withthe analyzer, X 50. B. A view of another portion of the same section as the previous, showing radiating brushes of delicate blue hornblende needles. Without the analyzer, X PLATE XLIV. PLATE XLIV. A. Diorite-porphyry, No. 298 S. N., showing the idiomorphic tendency of the plagio- clase and hornblende. With the analyzer, X 45. P = plagioclase phenocrystswith decomposed interior and rim of fresh feldspar; A = brown smaller plagioclases of the grouudmass likewise have idiomorphic ten-dency, so that the rock has a nearly panidiomorphic structure. B. Quartz-diorite-porphyry, No. 298 S. N., view of part of the same section as the previous, the section being made from a chip taken at the contact of the twodikes. The microcrystalline nature of the quartz-feldspar groundmass isshown, and in this groundmass are embedded plagioclase phenocrysts. Withthe analyzer, X U. S. GEOLOGICAL SURVEY SEVENTEENTH ANNUAL REPORT PART I PL. XUV
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