544: THE GEOLOGY OF NEWBRIDGE, NEAR BATHURST, N.S.W., 



soft and decomposed. The band of mica schist that lies between 

 the chiastolite slates and the granite vein is of tiiis type. A 

 second and more common type is seen among the granite veins 

 nearer the massif. It has a very fair cleavage, and on the 

 cleaved surface comparatively large flakes of mica can be seen. 

 The mica is arranged in black layers which alternate with grey, 

 finer-grained, less micaceous laminje. Junction-specimens of 

 slate and granite are easily obtained, and can with care be 

 sectioned (see Plate xxiii., fig. 3). Microscopically the slate is 

 recognisable by its unusuall}' large quartz grains, by the presence 

 of fairly large orthoclases free from inclusions, the abundance 

 and size of the muscovite flakes, and the complete absence of 

 sericite and carbonaceous matters. Biotite occurs in bright red- 

 brown crystals forming parallel bands which project from the 

 slate into the granite for a short distance from the line of contact. 

 This is probably due to the selective absorption of the schist 

 minerals by the molten granite, the quartz being absorbed more 

 than the biotite. The granite is devoid of coloured minerals for 

 about one-eighth of an inch from the junction. Small rutiles 

 occur in the slate, and some brown, pleochroic, perfect tourmaline 

 crystals. 



The schist that is in contact with the granophyre vein near 

 the 163J-mile peg is different from either of these types. It 

 would be easy to mistake it in hand-specimen for a blue slate, 

 save that it is black, and has not the same waxy translucency. 

 Microscopically it is very highly crystalline, though of fine grain. 

 Rock-flowage structure is typically developed. Quartz, biotite, 

 and carbonaceous matter are the chief minerals. Large clear 

 grains occur, with parallel rows of inclusions, and these Dr. 

 Woolnough believes to be potential andalusites. This mica 

 schist is very strongly intruded by the granophyre (see Plate xxiii., 

 fig.4). 



We have thus as a consequence of contact-metamorphism 

 first, the formation of knots in the blue slates. These pass later 

 into chiastolite crystals. B}' still further alteration the chias- 

 tolite slate passes into mica schist, which is the most metamor- 



