. The geology of the goldfields of British Guiana. AUGITE SYENITE, x 18,MAKARI, MAZARUNI RIVER. Photo hy J. NORITE, X 12,TAMUTAN, RUPUNUNI-TAKUTU WATERSHED. Flio/o hi/ J. IfiUiamf The Petrograpliy of the Granitic Rocks. 73 the microscope it is seen to be made up of large, irregular plates oforthoclase, of microcline, and some of oligoclase, a few of the latter arecrowded with microliths of epidote; with a very little quartz; and manylarge, more or less idiomorj^hic plates of green hornblende. A fewblebs of garnet, some small crystals and granules of sphene, and a littlelimonite are un
. The geology of the goldfields of British Guiana. AUGITE SYENITE, x 18,MAKARI, MAZARUNI RIVER. Photo hy J. NORITE, X 12,TAMUTAN, RUPUNUNI-TAKUTU WATERSHED. Flio/o hi/ J. IfiUiamf The Petrograpliy of the Granitic Rocks. 73 the microscope it is seen to be made up of large, irregular plates oforthoclase, of microcline, and some of oligoclase, a few of the latter arecrowded with microliths of epidote; with a very little quartz; and manylarge, more or less idiomorj^hic plates of green hornblende. A fewblebs of garnet, some small crystals and granules of sphene, and a littlelimonite are unimportant accessories. Augite-syenite.—Augite-syenite,moreor less altered,occurs in a broadbelt at the Makari Rapids, and in a narrow dyke at the Caburi Cataractson the Mazaruni River. The Makari rock consists of a porphyritic varietywith large phenocrysts of orthoclase, some of which are one and a halfinches in length ; and with some smaller ones of a pale brown pyroxenethickly scattered through a white matrix, in which, here and there, aretufts of small yellow ciystals of a mineral which probably is epidote
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectgeology, booksubjectp
