The Demerara River. ] 75 



chlorite after biotite. Above the falls the diabase has a coarsely 

 granular structure, and has weathered into rounded masses. 

 Near its contact with the gneiss its texture becomes finer, the ro3k 

 weathering into angular blocks ; and it gradually changes to a very 

 fine-grained basaltic diabase, which in the places of actual contact is a 

 very compact dense proterobase showing a fluxion structure. The 

 intrusive diabase mass sends out many narrow veins, which split up 

 and follow lines of weakness in the gneiss. In these the diabase is 

 converted into an epidiorite. 



The country in the neighbourhood of the Kanaimapoo, Appaparu 

 and Darina mines consists either of epidiorite, of epidote-hornl^lende- 

 schist or of quartz-schist and chlorite-schist. It is intruded into by 

 numerous dykes of diabase which give rise to ranges of low hills. 

 Quartz veins have been worked at these mines, but on tentative 

 scales only. 



