CARBONIFEROUS AND PERMOCARBONIFEROUS ROCKS, N.S.W. 291 



being red, green or brown. Quartz is inconspicuous to the 

 naked eye, the principal phenocryst being a white felspar. 

 Examined under the microscope the rocks are seen to have 

 been to some extent modified by the incoming of secondary 

 silica, which has formed patches of microcrystalline quartz 

 in the groundmass and has pseudomorphed some pyroxene(?) 

 phenocrysts. Porphyritic plagioclase '(andesine or labra- 

 dorite), quartz, a little ilmenite and an occasional biotite 

 flake are to be seen. The groundmass is cryptocrystalline 

 and plentifully besprent with pumice fragments. A couple 

 of specimens from a quarry on the road one and a half miles 

 beyond Paterson show generally similar characteristics. 

 One of them contains a number of angular fragments of 

 soda felsite. 



Andesites. — These naturally divide themselves into the 

 biotite-hornblende and the pyroxene groups, but transitional 

 forms exist. 



Biotite-hornblende Group. — This is what is elsewhere 

 referred to as the Martin's Greek type, from its extensive 

 development in that locality. It is however of very con- 

 stant occurrence all over the area, and has, within limits, 

 very constant characters which enable it to be readily 

 recognised in the field. It is usually of a blue-grey to pale 

 grey colour, is porphyritic in felspar and hornblende, and 

 often exhibits marked flow-structure in hand specimens, 

 due to parrallelism of the phenocrysts. The felspar is 

 andesine or acid labradorite, generally a good deal decom- 

 posed; orthoclase is absent. In addition to the hornblende 

 the microscope reveals subordinate biotite and magnetite 

 {? ilmenite) with a very little quartz occasionally. The 

 base is cryptocrystalline, with a variable proportion of 

 irregular glassy patches and streaks showing fluidal fabric. 



Among the contemporaneous flows of the Burindi series 

 there is found a type transitional to the pyroxene andesites, 



