542 THE GEOLOGY OF NEWBRIDGE, NEAR BATHURST, N.S.W., 



pressure has fractured the larger crystals, and recrystallisation 

 has to some extent induced a fiowage-structure, especially marked 

 by the biotites, though the llowage-structure is in most specimens 

 quite subordinate to the cataclastic structure. 



The fifth group is that of the Knotted Slates. Their chief 

 occurrence is in the railwa}'- cutting, between the augen slate 

 band and the granite massif. They are fine-grained, grey, with 

 a silky lustre and good cleavage. On cleaving, the flake will be 

 seen to contain dents or lumps up to the size of a grain of wheat; 

 and, if we polish the flake, the lumps will be found to have a 

 black core. I have not sectioned a specimen of this slate from 

 Newbridge, but an exactly similar rock occurs at the Wimburn- 

 dale Creek, as is described by Curran;^ and sections of it show 

 the following characteristics — the predominant mineral is quartz 

 showing rock-llowage. Brown biotite is very abundant, and 

 runs in strings parallel to the schistosity; it is not very pleochroic. 

 Carbonaceous matter is very abundant, and finely divided. 

 Some tourmaline occurs, and small rutiles, both well crystallised. 

 The black spots are aggregates of carbonaceous matter with some 

 magnetite. In one instance the boundary of a spot is almost 

 pure graphite, outside of which the biotites are arranged circum- 

 ferentially, so that a wave of extension passes round the spot as 

 the slide is rotated between crossed nicols. Generally the spot 

 is elliptical, but this instance is in the form of a prism with 

 terminal pyramidal faces. Inside the black border there is 

 carbonaceous matter intimately mixed with green and brown 

 biotite. These spots probably represented incipient andalusite^ 

 or chiastolite crystals. 



The second member of tliis group. Spotted Slate, is only the 

 oxidised outcrop of the Knotted Slates. It occurs in a band 

 running down the eastern side of the hill between Newbridge 

 and the granites, that is a band parallel and near to the junction 

 of slate and granite. This band is about 200 yards wide. In 

 hand-specimen it is medium to fine-grained, soft and reddish,. 



* These Proceedings, 1891 (2), Vol. vii., p. 201. 



