122 The Geology of the Gold Fields of British Guinna. 



been perceived from the description, they are over a complex of gneiss, 

 gneissose-granitite, and intrusive granites and aplites. The appearance 

 of the majority of them is deceptive ; only the low cataracts of Tuwarong, 

 Matope and Arikabusa impressing the inexperienced traveller with a 

 sense of danger. But the whirling rushes of water and the numerous 

 backwaters at the lower ends of the various rapids are recognised by 

 skilled boat hands as sources of many dangers. The loss of life in 

 this part of the Cuyuni has been great, but, fortunately, the Kamaria 

 road now offers an easy and practicable mode of avoiding the passage 

 of the cataracts and rapids with its attendant portages and delays 

 while going up the river, and its many dangers while descending. 



Masses of amphibolite are seen in an ochreous-coloured ferruginous 

 clay at the Upi^er Kamaria landing. About halfway between the 

 upper and lower landings of the road near the foot of a steep descent 

 rocks occur which, apparently, consist of a basic diorite, but which may 

 be an amphibolite or epidiorite. Between the Upper Kamaria landing 

 and a spot near the foot of Markabu Island rocks are not seen ; but a little 

 below the island is a rock of bluish quartz containing a few scattered 

 grains of pyrites. At the lower end of the island there are masses of 

 quartz exposed in the river, some of which are white and glassy in 

 appearance, while others are pink. Between the island and the right 

 bank of the river, and again at the head of a small island in the channel, 

 are exposures of a dark -grey schistose-quartz. The quartz yielded 

 upon assay gold at the rate of fifteen grains per ton of the rock. 



On the right bank of the river near the mouth of the Oko Creek, 

 and at the end of the Markabu Island opposite the mouth of the creek 

 there are broad exposures of fine-grained, almost compact, dark-coloured 

 hornblende-schist, with, in places, specks of pyrite, the rock varying 

 in structure from massive to iinely schistose. Similar rocks, showing 

 upon weathering a well-marked schistose structure, are seen at 

 intervals in tne river from the Oko Creek to the lower end of 

 Tiger Island, their schistosity being, in places, well marked. Above 

 Tiger Island the bed of the river is occupied by a broad expanse of 

 concretionary ironstone. 



The landing for the Groete Creek path is situated on the left bank 

 of the Cuyuni River about three-quarters of a mile below Tiger Island. 

 As already described, this path traverses a country of epidiorite and 

 hornblende-schists. Probably the Oko Hills, which appear to be a 

 continuation of the Blue Mountain Range on the right bank of the 

 Cuyuni, consist of hornblende-schist and amphibolite similar to those 

 exposed on the path. 



The only rock seen in the Mariwa Channel between the left bank 

 of the river and Tiger Island, is a mass of white quai'tz. Assays showed 

 that it contains only traces of gold. 



The Government Station is situated alxtut half a mile above Tiger 

 Island on the right bank of the river. It stands on a hill about sixty 

 feet high, the top of which is covered with a red earth with abundant 

 ironstone-gravel, which in places contains large masses of milky-white 

 (juartz. The slope of the hill from the river consists of a white friable 



