PRE-CAPE ROCKS OF THE NORTH OF THE COLONY 57 



kinds of granulites consisting of dark green hornblende, 

 blue augite, labradorite, sphene, and sometimes garnet 

 and epidote, the presence of the coarsely granular 

 quartz in the sharply denned lenticles that were 

 once steam-holes, gives the rock a very character- 

 istic appearance. The markedly schistose rocks are 

 usually made of quartz, felspar, tremolite, actinolite, 

 a much darker green hornblende, epidote, sphene and 

 magnetite with or without garnet. As the felspar de- 

 creases in amount epidote increases, and garnet also. 

 There is no sharp line of demarcation between such 

 rocks and those with a granulitic structure, but in the 

 granulites the hornblende is always actinolite or a much 

 darker variety. The blue augite is confined to the 

 granulites and does not occur in the markedly schistose 

 rocks ; to the north-east of the Kaaien hills the augite 

 is not deeply coloured, though colourless varieties are 

 very rare ; in the isolated patches of granulites south- 

 west of these hills the augite is more highly coloured. 

 In these western rocks, however, no amygdales have 

 been seen, and their relationship to the Marydale beds 

 is uncertain. 



In both the Marydale and the Kaaien beds there are 

 bands of grey granulite, often with the mineral composi- 

 tion of gneiss but grading into almost pure quartzite on 

 the one hand and into hornblende-granulite on the 

 other ; they sometimes contain cyanite, staurolite, and 

 sillimanite. It seems probable that much of this grey 

 granulite was of sedimentary origin. 



Though there is much doubt as to the original nature 

 of many rocks included in the Marydale beds, it is 



