600 GREAT SEKPENTINK-BKLT OF NEW SOUTH WALES, V., 



present in small amount. Specimen 1148 is a fine-grained, vesi- 

 cular, purplish-grey rock, with small, clear phenocrysts of albite, 

 one of which contains, in its central portion, abundant inclusions 

 of dusty magnetite. These phenocrysts have a roughly trachytic 

 arrangement. The groundmass consists of abundant minute fels- 

 par-laths, sprinkled with finely divided haematite. Quartz is pre- 

 sent in some amount, often chalcedonie, and a little chlorite occurs. 

 There are abundant large vesicles filled with calcite, and chlorite, 

 or quartz and chlorite. There is often a dense segregation of 

 dusty magnetite around the whole, or only a portion of the peri- 

 phery of the vesicles, and one can see that the zone of vesicles that 

 are most abundantly surrounded by magnetite, corresponds to a 

 zone of enrichment by magnetite of the main mass of the rock, 

 which lies on either side of a narrow crevice, running trans- 

 versely to the flow-direction of the rock. This is clearly illustrated 

 in tlie figure given (Plate Hi., fig. 3). The presumption is that the 

 magnetite in the rock lias been partly, at least, introduced pneu- 

 matolytically, and that surrounding the vesicles is due entirely to 

 this method of deposition. This is in accord with tlie results 

 obtained from the study of the Hyde's Creek complex in the 

 Nundle District(17). 



Rather different types of rocks, which, however, are clearly re- 

 lated to the above, are represented by specimens 1360 and 1363, 

 that occurred in association with the agglomerate in the complex 

 illustrated by Text-fig. 13. They were termed spilite-porphyrites 

 in the foregomg. The felspar-phenocrysts may reach 2 mm. in 

 length, are dusty and spotted with chlorite, slightly zoned, and 

 show pericline- as well as albite-twinning. The augite phenocrysts 

 are also large, 3mm. x 0*5mm. at most, are fresh or more or less 

 decomposed, and have a large optic axial angle (2V = 5'3°). Mag. 

 netite also occurs in large well-formed crystals. The groundmass 

 consists of lathy andesine-oligloclase, quartz in sharply defined 

 crystal-grains, and but rarely intersertal, granular augite, and 

 skeletal ilmenite, with small vesicles filled with quartz, chalcedony, 



