182 Tlt'i Gfioloijy of the Gold Fiddn of British GvAana. 



area near Akaiwanna on the EssequiVMj Iliver between Twasinki and 

 Great Itanime Rapids, which covers some sixty square miles. On 

 the Demerara Ri\er the only district of any importance is the small 

 one comprisiiifi aVjout thirty square miles in the neighljourhood of the 

 Kuniaparu lla})ids, and in which the hitherto only partially de%eloped 

 mines at Darina, Appaparu and Kainaimapu are situated. 



On the Berbice River there is a small area, of which it is not 

 possible to estimate the extent, lying between the Kuruduni Creek aiirl 

 the Tdurivvfwldi Cascade, which is somewhat auriferous, but, as far as 

 is known, not in any place to a payable extent. 



The geological structure of the Essequibo-Potaro-Konawaruk district 

 is far more complicated than are those of the districts situated to the 

 north-west of it. The placer gold has arisen from the degradation of 

 the older basic rocks, of the more recent diabase, and largely in places 

 from that of mineralised masses of acidic intrusives. 



Towax-ds the north-east of the district colours of gold have been 

 found in the gravels of the streams Mowing from the Arisaru Range. 

 The metal has Vjeen here derived from the degradation of the diabase 

 of which the hills consist. 



The district between Ararapira Point and Kuniaparu Point is 

 remarkable on account of the numerous, relatively narrow dykes of 

 diaVjase which traverse it. The diabase of these dykes always contains 

 minute proportions of gold diffused through the rock, whilst in places 

 at the edges of the dykes I have found that the proportions present 

 amount to from one to three pennyweights of gold to the ton of the 

 rock. This part of the district appears to me to Vje worthy of more 

 extended examination than it has yet received. 



Our knowledge of the geological structure of the Omai District is 

 more complete than it is of any other part (jf the colony. This is due 

 to the very extensive exploration work which was carried on by the 

 German Syndicate, and to the readiness with which their local agent, 

 the late HonouraV)le J. H. de Jonge, placed at my disposal the details 

 of the work and large collections of the rock-cores obtained by borings 

 put down, by the use of diamond drills, to depths of somewhat over 

 one thousand feet. Dr. Emil E. Lungwitz, of New York, who for 

 some years was in charge of the development work at Omai, presented 

 to the colony in 1901 a collection of drill-cores from the bore-holes 

 which were sunk under his superintendence at Omai, whilst he described 

 its geological structure in his monograph " Uber die regionalen 

 veranderungen der Goldlager-statten," and in the " Zeitschrift fiir 

 praktische geologic" for July, 1900. Mr. E. G. Braddon also added to 

 our knowledge in his paper entitlefl " British Guiana and its Mining 

 Development," published in The Mininf/ Journal, Railway and Com- 

 mercial Gazette, May and June, 1901. 



The country in the neighlxjurhood of Omai consists principally of 

 schistose rocks, intersected by a great roll of coarse-textured granite, 

 which extends from Kumaka to Krabbu Rapids, a distance of about three 

 miles. The rock varies in character and composition from a granitite, 

 containing such small proportions of ferro-magnesian minerals as to be 

 practically an aplite, to one containing consideraV)le proportions of 



