118 The Geology of the Gold Fields of British Gxdana. 



seen on both sides of the mouth of the Makauria Creek. In the rocks 

 on the south of the mouth of the creek, caught-up masses of gneiss 

 are noticeable in the granite. On this side of the river the granite- 

 belt appears to be about one and a half miles wide, the character of the 

 rocks exposed, and of the banks of the river to the south of it extending 

 as far as Kamarihuru Island, eight miles south of Bartica, indicating a 

 gneissose country. On the left bank of the river the exposui'es to the 

 mouth of the Cuyuni consist of the grey granite. On and near the 

 southern extremities of both Kaow and Calf Islands are exposures of 

 rocks, consisting of the grey granite, with, in places, included caught- 

 uji masses of grey gneiss. The rocks near Bartica point, and for 

 about a mile south of that point, on the Mazaruni River, consist of 

 gneiss and of hornblende-schist, probably a local modification of the 

 gneiss. To the north-east of Susan Island the grey granite occurs, and 

 is exposed on the island and on other rocky islets in that j^art of the 

 river. It is seen, veined with pegmatite, at the landing below the 

 Commissioner's house at Kalacoon ; in the quarries at Palmer's Point ; 

 at Barakara Cascades, and at Kyke-over-all Island. 



The second of a series of small islands, opposite the northern 

 boundary of the Penal Settlement, is largely made up of a mass of 

 quartz, about forty feet in length of which is exposed at low water, 

 whilst the small rocks in its vicinity indicate that the quartz occupies 

 a somewhat extensive area. Assays show that this quartz at its 

 outcrop does not contain gold. 



At the large quarries at the Penal Settlement the nature of the 

 grey granite is clearly seen. It is there traversed by veins of fine- 

 grained granite and by many veins of pegmatite. The pegmatite 

 contains small deep-red garnets and in places crystals of cloudy 

 greenish-grey beryl. 



The hill at the Penal Settlement consists of the residuary materials 

 of a basic hornblende-granitite-gneiss underlain by the grey granite. 

 At some earlier period the site of the Penal Settlement buildings 

 was a small island surrounded by the waters of the Cuyuni and 

 Mazaruni Riv-ers. 



The. Groete Creek. — Few rock exposures occur in the Groete Creek. 

 About one mile west of the mouth of the creek, near the Indian village 

 of Abanakari, on the right bank some masses of dark-coloured quartz 

 are lying in residuary clays apparently derived from gneiss. 



Rock exposures occur in the Groete Creek at about three miles from 

 its junction with its tributary the Black Creek. For a distance of 

 about one hundred yards rocks are exposed at intervals, consisting of 

 gneiss traversed by a narrow intrusive vein of olivine-diabase. The 

 banks of the creek, wherever clean sections are exposed, consist of the 

 residuary clays from feldspathic gneiss. Beyond the exposures of 

 gneiss the banks become lower, while the channel of the cx-eek consists 

 of siliceous sands. The course of the Groete Creek is mainly through 

 a gneissose country. 



On the left bank, a little below the mouth of the Black Creek, a 

 small creek — Salt Creek — falls into the Groete Creek. This has its 



