The Stnu'tiircs of the Auriferous Dhtricts. 181 



Issano River in a iiorth-uorth-westerly direction, a distance of about 

 forty-five miles, to the Kartuni River ; and from the latter for a 

 distance of nearly thirty -five miles to the head of the Kopang. The area 

 of this district, as far as it is known, is approximately one thousand 

 square miles. The small auriferous fields on the Kaburi Rivei', the 

 Samang River and the Jsenaro Creek have a combined area of about 

 one hundred and sixty square miles. The main source f»f the allu\ial 

 gold in the district is, as in the greater part of the JSTorth-Western 

 district, the older basic rocks now represented by epidiorite and 

 honil)lende-schist. A broad belt of tliese rocks extends in a south- 

 westerly direction from the Blue Mountains, south-west of the Groete 

 Creek, to the neighbourhood of the Issano River, a distance, as the 

 crow flies, of about eighty miles. Many placer claims occur along 

 this belt, while in it, near the western bank of the Puruni River, the 

 great mass of highly auriferous quartz worked at the Peter's Mine 

 occurs. As far as is known diabase is not of much importance as 

 a source of placer gold in this district, but in the area between 

 Tinaniu and Paiyuka Cataracts on the Cuyuni River the extrusion 

 of three or more great diabase-dykes has resulted in the mineralisation 

 of the granitite-gneiss through which they have passed. 



In the north-westerly part of the district liberation of the placer 

 gold is the result of the decomposition of relatively more or less acidic 

 schistose rocks, and of consolidated tufis and chloritic-felsites. As a 

 general rule the placers in this part of the district are not very 

 productive. 



Near the Warden's reserve, south-east of Arawak Matope Cataracts, 

 placer gold has been derived from sericite-schist and the masses of 

 quartz contained in it. 



The source of gold on the Samang River is probably the residuary 

 deposits from diabase ; while that in the rich placers formerly worked 

 by Barnard & Co., near the Isenaru Creek, comes from a mica-gabbro. 



Gold occurs in very minute quantities in rocks of all types in 

 the Mazaruni River district, liut it is seldom sufficiently concentrated 

 in any of them to give rise on their decomposition to payable placer- 

 deposits. 



(c) The EsiSPipiiho, Polar o, Konawaruk and Demerara Rivera 

 District. — The principal auriferous area in this district is the highly 

 productive one which extends from Ararapira Point on the Essequibo 

 River, to the first cataracts on the Kuriebrong River, a distance 

 from east to west of al:)out forty miles ; from the south-west end 

 of the Arisaru Range in a south-westerly direction to somewhat 

 south of Two Mouth on the Konawaruk River, a distance of a 

 little more than forty-five miles ; from the latter place in a north- 

 north-westerly direction to Pakatuk Cataracts, a distance of about 

 seventeen miles ; and in a northerly direction for nearly twelve miles 

 from Pakatuk to the lowest cataracts on the Kuriebrong River. Tliis 

 very important area, in round figures, extends over four hundred and 

 fifty square miles. There is also a less important and much smaller 



