370 UKEAT SERPENTINE BKLT OF NEW SOUTH WALES, \ li., 



The jjijrojienic keratoplii/res are those line- and coarse-y rained 

 types of rocks, wliicli are intermediate in composition between tlie 

 dolerite-spilite group, on the one hand, and the t'elspathic kera- 

 tophyre on the other. They may or may not contain quartz. As 

 instances of these may be deiicribed specimen No. 1414. This is a 

 pinkish rock of medium grainsize and syenitic appearance, occur- 

 ring a quarter of a mile soutii of the point where Sandy Creek 

 enters the Parish of Loomberah. It is granitic in texture, con- 

 sisting of grains of albite up to 1 mm. in diameter, irregular 

 prisms of augite partly uralitised or altered to chlorite, prisms of 

 apatite, and a minor amount of spliene in irregular grains. 



The western keratophyre-zone is exemplilied bj' two rocks, which 

 may be classed with the pjroxenic keratophyre-group. At the 

 northern end of this zone, in Portion 31, the keratophyre (No. 

 141.3) is porphyritic with phenocrysts of albite, augite, now com- 

 pletely chloritised, and ilmenite associated with small crystals of 

 apatite in a glomero-porphyritic .aggregate lying in a pilotaxitic 

 base of laths and .small phenocrysts of albite with interstitial 

 quartz. Further south, on the same belt, just east of Black Jack, 

 occurs a rock (No. 1383) rather more pyroxenic than this. It is 

 dark green in colour, consisting of well crystallised albite-laths, 

 generally about 0*2 mm. in length, together with small phenocrysts 

 of the same mineral 1 mm. in diameter, partly replaced by chlorite 

 zonally arranged. Interstitially between the felspar-laths is a 

 small amount of devitrified glass. The augite occurs in small 

 grains often more or less chloritised, and, in addition, there is a 

 fair amount of magnetite. The keratophyre of this zone is, how- 

 ever, usually more acid than this, as instanced by specimens 

 described below, and the highly siliceous rocks near Pipeclay 

 Creek. 



Bearing in mind Neithammer's suggestion (18), supported by 

 E. B. Bailey (19), that keratopliyres are often only albitised 

 porphyrites, we may include in this group specimen No. 1123 from 

 the Nemingha Red Breccias (Portion 58). It is closely alHed to 

 No. 1116 described above (p. 369), and contains idiomorphic 

 l)henocrysts of plagioclase, in wliicli a little original andesine 



