BY L. KEITH WARiD, B.A., B.B. 



^37 



the development of haematite. In other varieties, again, 

 the colour is dark gre}^, from the presence of some 

 colouring matter the nature of which is obscure. Some 

 of the dark varieties are clearly graphitic, but are not 

 commonly seen. 



In the upper part of the Collingwood River valley 

 some garnetiferous varieties have been found by the 

 writer. And near the latter, as elsewhere throughout 

 the neighbouring district, there are present some em- 

 "bryonic minerals in the schist which, from their pre- 

 sence, exhibits knots and complementary depressions 

 on the cleavage surfaces. 



The quartzites found among these markedly schis- 

 tose rocks are frequently perfectl}^ free from all signs of 

 foliation. They are almost always pure white in colour 

 and extremely dense in texture. 



The freedom from foliation in these rocks is prob- 

 ably largely due to an original purity of composition. 

 The absence of the foliation, nevertheless, appears re- 

 markable when the quartzitic beds, perfectly free from 

 visible schistosity, are seen interlaminated with the 

 foliated mica schists. The microscopical characters of 

 such quartzites have not yet been studied. 



It may be that the quartzitic bands have moved as 

 a whole before the crushing forces. However, it ap- 

 pears to the writer more probable that the foliated ap- 

 pearance of the micaceous schists is largely cau&ed by 

 recrystallisation under pressure rather than by actual 

 displacement of adjacent particles. Over and above this 

 foliation there has been induced also, in very many 

 cases, elaborate crumpling; but a foliated texture may 

 result where crumpling has not occurred. It will be seen 

 later that in some places the quartzites are folded and 

 fractured. 



Summing up, the several schists of which mention 

 has been made must undoubtedly represent a great 

 aeries of sediments — psephites, psammites, and pelites 

 — which have suffered dynamical metamorphism. 



This Hthological division of the Pre-Cambrian com- 

 prises by far the larger portion of the rocks to which 

 reference is made in this paper. 



