598 GREAT SERPENTIXE-BELT OF NEW SOUTH WALES, v., 



The soutliern end of this mass is very fine-grained, and-exeeed- 

 ingiy vesicular, and passes without any definite break into the mass 

 of p^^'oclastic rocks that are described below. 



A single sill of spilitic dolerite invades the clayslates, at the 

 Municipal Quarry in the Tamworth Common. It is a rock of 

 medium to fine grainsize, with a subvariolitic texture (1018). The 

 felspar is clear albite, with a few inclusions of chlorite. It forms 

 long plates with occasional skeletal extensions. Intersertally are 

 minute laths of felspar, and a small amount of granular quartz, 

 mixed with a considerable amount of chlorite. Many small, brown 

 grains of augite occur, together with a few larger ones, which are 

 fairly fresh. There is also a little magnetite. Some secondary 

 carbonates are present. 



Specimen 1303, which represents what is probably a small intru- 

 sion in Portions 213 and 216, Nemingha, is a most interesting rock. 

 In hand-specimen, it seems to be a normal but rather decomposed 

 dolerite, with large augite-phenocrysts. The microscope shows that 

 its constituent grains are mostly shattered. The phenocrysts are 

 large, zoned augites, similar to those occuring in certain andesites 

 and porphyrites. The edges of the broken fragments of them are 

 quite sharp, and show no sign of resorption. Generally they are 

 yellow-brown or green, and are markedly pleoehroic. Frequently 

 adhering to these crystals are fragments of green partially chlori- 

 tised glass, containing laths of acid plagioclase and spherulites of 

 chlorite. This adheres only to the crystal-edges of the augite, it is 

 not found against the fractured edges. The fragments of crystal 

 and glass alike are embedded in a groundmass, which consists of 

 irresolvable, apparently partly felspathic decomposed matter, 

 which seems to have been produced by the pulverisation of felspar- 

 phenocrysts, together with fragments of pyroxene, chlorite, epi- 

 dote, calcite, and rarely a little magnetite. This rock is best con- 

 sidered as a brecciated, hypocrystallite augite-porphyrite. (See 

 Plate lii., fig. 2.) 



KeratopTiyres. 

 These are far less frequent in the massive condition than the 

 spilites or the dolerites, though they are very abundant in the 



