1 G6 Tlie Geolofiy of llip. Gold Flplds of British Gn,iana. 



rock. A dyke of coarse diabase crosses the Gloria Creek between 

 Gloria Placer and Quintette. The road from Gloria Placer passes over 

 (]uart7-sand until it joins the Potaro Road about seven and a half miles 

 from Potaro Landing. 



The Potnro-Konawamk Road. — The Potaro-Konawaruk Road starts 

 at Potaro Landing from a hill of red clay, the degradation-pi'oduct 

 of diabase, and for some miles the hills traversed by the road, as a rule, 

 show the same characteristics. In places the hills are covered with 

 white siliceous sand, and in others with concretionary ironstone. Here 

 and there, for instance at near the third and fifth miles, boulders of 

 diabase of varying texture are found in the Ijeds of little creeks crossed 

 by the road. Jn the valleys, and on some of the hill sides, the road 

 passes through or over white or light cream-coloured sandy clays clearly 

 derived from granitic or felsitic rocks. The low hill on which is the 

 road camp, near the eight mile post, is an example of this. A little 

 beyond the road camp, at this place, the road passes through a cutting 

 in red cla^^, containing ironstone-gravels and small boulders of diabase. 

 Ironstone-gravels on the hill-sides, and red or ochreous clays, are the 

 prevailing characteristics of the road from here until reaching the 

 Inflexible Syndicate's Camp. On the roadside from the camp, 

 descending the hill to the Mahdia Flats, where the placers of the 

 syndicate are situated, there are some very large boulders of 

 concretionary ironstone. 



Near the Mahdiana workings of the Inflexible Syndicate, south-east 

 of the camp, a compact felsite and a coarsely crystalline augite- 

 granophyre, with narrow veins of quartz and with much iron pyrites, 

 occur. Samples of the latter rock have yielded upon assaying at the 

 rate of from two and one-eighth pennyweights of gold to the ton to as 

 much as fifteen pennyweights. In the forest near the Mahdiana 

 workings there are two very large boulders of conglomerate, or 

 pudding-stone, resembling in character the conglomerate of the 

 Kaieteur Plateau. These, pi'obably, are remnants or outliers of tiie 

 sandstone-formation which in former ages extended much farther in 

 a north-easterly direction than it does at present. 



The Mahdia is a large stream with a north-westerly and south- 

 easterly course, flowing into the Potaro River above and at a distance 

 of about three miles south-west of the Pakatuk Cataracts. The 

 iluviatile deposits of sand and gravel along its course are everywhere 

 auriferous to a greater or less degree. Unfortunately the flats on the 

 lower parts of its course are very subject to flooding by the waters of 

 the Potaro, and hence but little has been done in the way of working 

 that part. The Mahdia Valley is filled by a fluviatile deposit of sandy 

 cl-iy of an ochreous colour, which is underlain by auriferous gravels. 

 The bed-rock of the placers is a light-coloured or bluish-white sandy 

 clay, evidently derived from the degradation of acidic rocks, probably 

 of quartz-porphyry. In places the whitish clay is crossed by belts of 

 sandy clay, which are deep ochreous to dark-red in colour, and which 

 doubtless represent former dykes of basic rocks. 



