lxxiv. Timehri. 



was being worked in the earlier mouths of 1897 but temporarily closed 

 down about the middle of that year. Both mines are now closed down, 

 the former perhaps on account of the excellent and scientific exploitation 

 by which the really payable sections of the reef — a quartz-aplite vein in 

 a chloritic actinolite-schist — were removed and crushed, leaving only its 

 relatively poor areas for future working ; the latter because the reef split 

 into a plexus of small quartz veins and threads as the workings reached a 

 diabase-sill which traverses the country, there an altered aplite. The 

 shaft was driven into the sill for several feet, but as the rock was there of 

 coarse texture, indicating that the sill might be of considerable to great 

 thickness, the working was abandoned. 



Dredging for alluvial gold is being, and has been for several years, 

 carried on successfully on the Konawaruk River and on the Mahdia and 

 the Minnehaha creeks of the Potaro goldfields. Hydraulic workings 

 were carried on for the exploitation of the gold in the weathered aplite 

 and the laterites of Omai, Essequibo River ; and in the weathered chloritic 

 and sericitic schists at Tassawini on the Baraina River. The former was 

 very successful in its recovery of gold from the aplite ; the latter did not 

 meet with much commercial success in its exploitation of low-grade 

 schistose material. 



At first sight it would appear as though the prospects of our country 

 for the future production of gold are gloomy in the extreme. This is not 

 so ; and I am satisfied that sooner or later after the termination of the 

 war the prospects will very greatly improve. There are — there must be 

 — other valleys in the vast interior of the colony having a structure similar 

 to that of the Mahdia and Minnehaha valleys, a country of more or less 

 auriferous aplite and aplitic granite intersected by the many feeders of one 

 of the great sills of diabase which are so characteristic a feature of the 

 interior of Guiana. The igneous and metamorphic rocks of the colony are 

 practically all auriferous, carrying either original or far more usually secon- 

 dary gold, the metal being of course present in them in only very minute 

 proportions. The great geological age of the country has resulted in the 

 destruction of the auriferous quartz-aplite veins with resultant concentra- 

 tion of their gold-content in their remnants. This has given rise to reefs 

 exceptionally rich in gold at their present outcrops owing to secondary 

 enrichment, but becoming non-payable or petering-out at depth. There 

 must be other enriched masses and reefs not yet found to reward the fut- 

 ure prospector. There are vast masses of auriferous aplite, closely allied 

 to alaskite, in parts of which the gold-content has been concentrated to 

 payable extent by the action of intrusive dykes of diabase, of other aplites 

 or of micro-pegmatite. There are vast areas of ancient gabbros and 

 norites, — now epidiorites,hornbleudic or chloritic schists, — with their gold- 

 bearing debris, auriferous laterites. There must also be streams with 

 payable auriferous gravels in their beds other than the Konawaruk, the 

 Mahdia and the Minnehaha which will amply reward scientifically con- 

 ducted dredging-operatians. 



