1 08 The, Geohifiy of tlic. Gold Fidds oj British Guiana. 



The Barima River. — Low lulls of more or less decomposed 

 hornblende-schist occur on both banks of the Barima River at 

 Mount Everards, Mount Terminus and near the Goodewi Creek, 

 about 46 miles from Morawhanna. The gravels derived from them 

 are probably more or less auriferous. 



At Koriabo, 20 miles from Mount Everard, is a low hill of red 

 ferruginous earth, the residue of a diabase, resting on cream-coloured 

 sandy clays derived from gneiss. I detected in the red earth minute 

 colours of gold. 



The Barima River in its course from Koriabo to near Mclntyre's 

 Lauding has cut its channel through the basal gneiss of the colony. 

 This is intersected at BamV)oos, and at between two or three miles west 

 of that i:)lace by dykes of diabase, the positions of which are shown by 

 the occurrence of red clays and concretionary ironstones on the banks of 

 the river. Near to an old Indian settlement to the east of Queaque Creek, 

 at a place known to the gold-diggers as " Flat Rock," the gneiss is 

 intersected by a broad outcrop of a grey-coloured gneissose granite, a 

 considerable area being exposed when the water in the river is low. 

 To the westward of this place some narrow dykes of diabase traverse 

 the gneissose rocks. From near Mclntyre's Landing to the foot of 

 Mekorerusa or Eclipse Cataracts, the exposures along the course of 

 the river indicate that the country is generally a schistose one, there 

 being exposures of quartz-schist, chlorite-schist, and of more or less 

 decomposed mica-schist. In places the schists are cut through by 

 dykes of diabase, which cross the course of the river between the 

 great masses of that rock which form the hills on its banks. These 

 dykes are more frequent and of larger size in the district between the 

 lower mouth of the Manicuru Creek and that of the Arakakaparu Creek 

 than elsewhere in this part of the colony. 



Only the larger of the dykes are recognisable, except when the water 

 in the river is very low, and even then the smaller ones are more usually 

 indicated b}^ the presence of bars of more or less tenacious red laterite 

 than by that of the unaltered greenish-grey to blackish-grey rock. 



The Mekorerusa, or Eclipse Cataracts, are over a granitite of a 

 decidedly gneissose character. The rock is grey in colour, and some- 

 what coarse in texture. At Yakiri Creek it is crossed by an intrusive 

 dyke of a fine-grained biotite-diorite, the outer parts of which, where in 

 contact with, or close to, the granitite, show well-marked schistosity, 

 due to fluxion in the pasty mass during its intrusion. 



At Uropocari Rapids the gneissose granitite, which is similar to that 

 at Eclipse Cataracts, is traversed by many narrow veins of intrusive 

 basic rock. Near to these the granitite is altered, and shows a foliated 

 structure. 



Near Duquari Creek, for a distance of about one and a half miles, 

 the granitite is traversed by a dyke of epidiorite, which, in parts, has a 

 massive structure, and in others a schistose one. 



Above Duquari Creek the Arawatta rocks form a marked feature 

 in the scenery of the river. They consist of a grey-coloured, fine-grained, 

 '^aieissose granitite, which rock is also exposed at intervals for about two 



