. The geology of the goldfields of British Guiana. GRANITITE GNEISS, x 12,KAPASI, MAZARUNI RIVER. Phofo by ./. HORNBLENDE GRANITITE GNEISS, x , MAZARUNI RIVER. Photo In/ J. miliamf. Tlhe Petrography of the Fundamental Gneissose Complex. 33 plates of muscovite are present; laths of olive-green biotite are iu partsirregularly scattered through the rock, and in others they form streams ;much of the biotite is more or less chloritised, and in places is completelychanged into chloiite ; in a few specimens sparse granules of pyroxeneare present, while in some others pale-green hor
. The geology of the goldfields of British Guiana. GRANITITE GNEISS, x 12,KAPASI, MAZARUNI RIVER. Phofo by ./. HORNBLENDE GRANITITE GNEISS, x , MAZARUNI RIVER. Photo In/ J. miliamf. Tlhe Petrography of the Fundamental Gneissose Complex. 33 plates of muscovite are present; laths of olive-green biotite are iu partsirregularly scattered through the rock, and in others they form streams ;much of the biotite is more or less chloritised, and in places is completelychanged into chloiite ; in a few specimens sparse granules of pyroxeneare present, while in some others pale-green hornblende is found insmall quantity: occasionally epidote is present, apparently in originalcrystals, but more commonly as secondary granules. Grains of sphene,of garnet, of magnetite and of ilmenite, with, in places, leucoxene,minute crystals of apatite, of zircon, and rarely of rutile, form unim-portant accessories. 3. Granulitic.—Parts of the gneiss where the dynamic forces havebeen more intense show not only a well-marked foliated structure butthe quartz and feldspar are granular. Specimens of this have beenobta
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