348 GREAT SERPENTINE BELT OF NEW SOUTH WALES, vii., 



nearly half a mile wide, and includes a band of a peculiar por- 

 phyrite (see p. 369, specimen 1435). In lithological character, 

 the agglomerate is very like that in the band described last. It 

 may be traced continuously to the south, becoming narrower all 

 the way, until it dies out near the Pipeclay Gully. 



Massive Igneous JRocks. 



The Keratophyres. —The most striking feature of the massive 

 igneous rocks is the occurrence of a second long zone of kerato- 

 phyres extending from near the northern end of the map to the 

 southern. The northernmost occurrence in this zone appears to 

 be the few small sills at the head of Oakey Creek, in the Parish 

 of Nemingha; but, further south, there is the keratophyre- 

 complex by Macllveen's, which clearly belongs to the zone here 

 discussed. It has been already described (6, pp.57 1-3). South 

 of the Peel River, keratophyre appears again in Portion 55, 

 Loomberah, where there is a very inconspicuous outcrop of vesi- 

 cular, magnetite-bearing keratophyre to the M'est of Sandy Creek. 

 Beside it, there rises Jasper Knob, a huge mass of jasper, some- 

 times almost saccharoidal or miarolitic, with chalcedonic quartz 

 and finely divided platey haematite, not at all smooth and uniform 

 like the jaspers of the Eastern Series. The hill is about 200 

 yards long and over 100 yards in width, and is crowned by great 

 crags of jasper rising about 150 feet above the creek. To the 

 north and south, the country-rock is more or less jasperised 

 claystone. There can be no doubt that the presence of the 

 jasper is due to the impregnation or replacement of the claystone 

 by ferruginous solutions emanating from the keratophyre, just as 

 was shown in earlier papers {e.g., 5, pp. 133-4, 137, 164; 6, p. 57 2). 

 There is, however, a remarkable disproportion between the size 

 of the mass of jasper and the small amount of visible keratophyre. 



Passing to the south, no more keratophyre belonging to this 

 zone appears for a distance of about four miles. Then it is seen 

 forming the low ridge in the east of Portion 31, the red breccias 

 and Nemingha limestone occurring along its western margin. 

 It is here a porphyritic rock, with large phenocrysts of acid 

 oligoclase in a finely trachytic base, in which a little quartz is 



