350 GREAT SERPKNTINE BELT OF NEW SOUTH WALES, vii., 



tion 61, whence it may be traced througli Portions 59, 58, and 

 57. The largest mass lies nearly three miles further to the 

 south, namely, in Portions 24 and 35. This is an almost granit- 

 oid rock characterised by the presence of strongly zoned plagio- 

 clase, chiefly labradorite, and hypersthene in association with 

 augite and ilmenite. An analysis of this rock, 1387, is given 

 below (p.368). 



It is not clear whether any of the dolerites further to the 

 south, such as that in Portion 37, should belong to this group, 

 though they were originally possessed of basic felspar, now partly 

 changed to albite and prehnite. 



The Porphy7'itic Dolerite is intimately associated with the 

 Nemingha Red Breccias, and, therefore, has invaded a somewhat 

 lower horizon than the hypersthene-dolerite. It appears in 

 typical form, east of the limestone in Portion 59, as a handsome, 

 dark green rock (1407). It has pale green phenocrysts of acid 

 labradorite and dark chloritised augite, while the peculiar spongy 

 fabric of the base suggests a relationship to the keratophyres. 

 A much larger mass occurs in Portion 32. This occurs intrusive 

 into the Nemingha Red Breccia. In between these two masses, 

 the large and small fragments of porphyritic rocks in the 

 Nemingha Red Breccia have features strongly suggestive of close 

 association with, if not original membership of this group of 

 intrusions. The ferruginous, albitising solutions have, however, 

 strongly attacked the rocks, changing pyroxenes into iron-ores 

 and carbonates, while plagioclases, originally basic, have passed 

 into albite and carbonates. These have thus become kerato- 

 phyres through the alteration of dolerite-porphyrites, a process 

 analogous to that described by Neithammer(18) and E. B. Bailey 

 (19), and they are associated with fragments of normal trachytic 

 keratophyres, more or less impregnated with ferruginous solutions. 



It is possible that these porphyrites may be connected with 

 the porphyritic spilites on East Gap Hill, in the Parish of 

 Nemingha(6, pp. 596-8). The latter pass without break into a 

 red breccia identical in all respects with the Nemingha Red 

 Breccia. The porphyritic rocks are not, however, identical. The 

 East Gap Hill rock has suffered to a greater or less degree from 



