CARBONIFEROUS AND PERMO-CARBONIFEROUS ROCKS, N.S.W. 265 



beds; it gives good outcrops at Wallarobba between the 

 railway station and the Wallarobba Tunnel. Good outcrops 

 occur at Eelah (in the Parish of Gresford just north of the 

 Hunter River), and from here it can be traced to Hudson's 

 Peak and Lamb's Valley. This rock is dark blue in colour 

 with abundant small phenocrysts of augite, hornblende and 

 plagioclase with occasional phenocrysts of quartz. Its 

 microscopic characters have already been described by 

 Mr. Aurousseau. (8) 



The Hyper sthene Andesite Glass. — This is a very wide 

 spread lava flow; at Martin's Creek and the Gilmore Range 

 it is the next flow after the Martin's Creek andesite. It is a 

 pitch-black rock with numerous phenocrysts of plagioclase. 

 Under the microscope it displays a glassy base in which 

 are embedded abundant plagioclase phenocrysts with fairly 

 abundant hypersthene. It varies from 150 to perhaps 400 

 feet in thickness. 



The Dacltes. — There are from three to four of these flows, 

 but they are all of somewhat similar character. The un- 

 weathered rock has a bluish-grey colour, but the partly 

 weathered rock may be green, red or pure white, pheno- 

 crysts may or may not be present, when present they con- 

 sist of quartz (variable in amount), felspar and biotite, the 

 latter occasionally very abundant. Generally much of the 

 rock consists of volcanic glass which may be more or less 

 devitrified. Although fairly acidic these rocks do not 

 always give good outcrops, and it is difficult to secure 

 specimens that are quite free from decomposition. They 

 frequently contain small fragments of aphanitic igneous 

 rocks which probably represent older rocks which were 

 melted up to form this lava. Some of these rocks upon 

 analysis may prove to be rhyolites, in fact the field evidence 

 suggests that a flow which is a dacite in one locality may 

 merge into a rhyolite not very far away. The possibility of 



