576 GRKAT SKRPENTINE-BELT OP NEW SOUTH WALES, V., 



Nemingha. It was, unfortunately, not exactly localised, and 

 the writer could not find it on a second visit to the place of its 

 discovery. It is described below (see p. 598). 



The intrusions of dolerite at the extreme south and north of 

 the long complex, of which East Gap Hill is the central part, 

 are normal dolerites, the felspar of which is labradorite; but 

 several specimens from the central portion of this mass are 

 albitic. So far as can be seen, there is no evidence of the forma- 

 tion of adinole in the cherts, associated either with the albitic 

 or the non-albitic dolerites, nor is there any difference recognisa- 

 ble in hand-specimen between the two types of intrusive rock. 

 Tlie microscope shows that the albitic rocks are thoroughly 

 uralitised, but some of the calcic dolerites are also considerably 

 altered. The dolerite in Portion 166, Nemingha, contains veins 

 of epidote, with which is associated a large amount of axinite. 

 The discovery of this is due to Mr. D. A. Porter. Axinite also 

 occurs in the vesicles of the spilite-porphyrite on East Gap Hill. 

 Nothing more can be said as to the source of the axinite than 

 was said concerning that of the Nundle district, namely, that it 

 probably is derived from the basic rocks themselves, and is not 

 necessarily a product of the intrusion of the not very distant 

 granite (see 17, p. 126). 



There are, finally, a few small intrusions of quartz-keratophyre, 

 of which the largest occurs on the extreme south of the area 

 studied, Portion 171, Nemingha, while a series of smaller intru- 

 sions are to be found along the eastern side of the East Gap Hill 

 zone of igneous rocks, and an isolated occuri-ence a quarter of a 

 mile north of Housefield's Hill in the Parish of Woolomol. The 

 characteristic feature of these rocks is the very great amount of 

 strain-effect which they exhibit: the rock breaks with a peculiar 

 jagged fracture, the felspars are often bent and broken, and the 

 grains of quartz are shattered and ragged, with very undulose 

 extinction. The reason of this great exhibition of pressure- 

 effects is not at all clear. One may recall the fact that the 

 keratophyres of the Nundle district showed strongly brecciated 

 structures, and the suggestion made previously (17, p.l64), that 

 possibly these rocks owed their character to movements acting 



