152 GREAT SERPENTINE BELT OF NEW SOUTH WALES, iv., 



There are also rocks of a more obviously brecciated appearance, 

 angular fragments of black rock in a pinkish background. These 

 show a brecciated structure similar to that of the foregoing; 

 that is, they are divided up into areas, in which the general 

 direction of the trachytic texture has no relation to that in the 

 adjacent areas, and this diversity of How-direction is seen both 

 in the parts rich in magnetite and in those free from that mineral. 

 As in the last rock, also, albite crystals may project from the 

 dark ferruginous part into that surrounding it, which is com- 

 posed entirely of felspar. The limits of the ferruginous parts 

 are quite irregular; though, in handspecimen, they may appear to 

 be very sharply bounded, under the microscope, they are seen to 

 pass into non-ferruginous parts(Pl.xxvii.,f.4). In a few instances, 

 the magnetite-keratophyre fragments are wrapped round by purely 

 felspathic rock, in which the felspar laths are arranged circum- 

 ferentially about it. Magnetite may also occur in cracks travers- 

 ing the rock, sometimes running between adjacent trachytic 

 patches, sometimes cutting across a single fragment. There are 

 also segregations of magnetite lying isolated in areas usually free 

 from that mineral Chlorite occurs in large flakes. As regards 



actual mass, the magne- 

 tite is considerably less 

 abundant than the fel- 

 spar, but the very minute 

 grains and crystals are so 

 abundant that they ren- 

 der the whole portion of 

 the rock in which they 

 occur almost black. Fig.6 

 is a diagram showing the 



structure of these rocks. 

 Text-fig. 6. — Diagram showing the structure ^ . 5 i ^.r 



^ \ . ^ J ,.^ f ^ , For clearness' sake, the 



of a brecciated magnetite-keratophyre. 



size of the felspars has 



been enlarged proportionately to that of the individual rock- 

 fragments. 



A variety of the brecciated structure is seen in a few rocks, 

 in which the fragments of trachytic rock are not in contact with 



