200 The Geologu of the Gold Fields of British Guiana. 



Tlie Mariwa Placers (jii the western slopes of the Blue Mountains 

 resemble in general characters the Groete Creek Placers, but, as 

 a rule, their gravels yield lesser proportions of gold. 



The Arimu Creek placers in the lower parts of the creek, where 

 undulating sand-hills form the country, have for their pay-dirt fine 

 angular, white, and ferruginous quartz gravel, with, occasionally, larger 

 pebbles of quartz. Where these pebbles show a schistose structure 

 specks of free gold are not uncommon in them. The upper placers are 

 situated some miles from the course of the creek, where the country 

 consists of low hills of ferruginous clays, capped with large boulders of 

 concretionary ironstone. In these placers the gold-bearing gravels are 

 generally about one and a half feet in thickness, and are covered with 

 from six to ten feet of yellow and reddish clays, with, in their lower 

 parts, layers of white sand and clay. The gravels consist of fine and 

 coarse, angular brown quartz, and, in places, have yielded as much as 

 seven pennyweights of fine gold per cubic yard. In the highest parts 

 of the disti'ict towards the water-shed, between the Cuyuni and Puruni 

 Rivers, the overburden averages about four feet in thickness, and it 

 rests on about two feet of gravel, which has yielded about five 

 pennyweights of fine gold per cubic yard of the pay-dirt. 



The Quartz Stone Placers are about twelve miles from the Cuyuni 

 Kiver. Their strippings consist of an average depth of three feet of 

 yeliowish-red clay, which is underlain by about two feet of white 

 angular quartz gravel, intermixed with sand and clay. The quartz 

 occasionally shows free gold. The gold in the gravels varies frora fine 

 dust to large nuggets, and shows no signs of having undergone 

 transportation. 



The Waiamu Placers are scattered over a wide area. Their gold- 

 bearing gravel is of a coarse angular quartz, with a good deal of sand, 

 yields about one and a half to two pennyweights of gold per cubic 

 yard, and is overlain by about three feet of ferruginous clay. 



The St. John's Placers usually have an overburden of about four 

 feet of an ochreous-yellow clay, and their gravels — -consisting of coarse, 

 angular fragments of quartz, intermingled with pebbles of more or less 

 decomposed felsite, and, in places, with many nodules of concretionary 

 ironstone — vary in thickness from one to three feet. The gold found 

 is coarse, and is very unevenly distributed. 



The Kopang Placers are situated towar*"^ the head of the creek 

 near the Barama disti'ict. As a rule the overburden of brown clay is 

 not deep, and the gravel consists of coarse quartz pebbles which do not 

 show visible gold. The gold obtained is usually fine-grained, and the 

 gravel has yielded at the rate of two to three pennyweights of the 

 metal per cubic yard of pay-dirt. 



The Mazaruni and Puruni Placers. — The Puruni Placers are the 

 more important of these. They have an advantage over most of those 

 in other districts of the colony in being, as a rule, relativelj'^ near the 

 banks of the river. Some are situated almost directly on them ; whilst 

 the average distance of the placers is not more than four miles from 



