596 GREAT SERPENTINE-BELT OF NEAV SOUTH WALES, V., 



quite idiomorphie, and either isolated, or associated in glomero- 

 porplija'itic aggregates, which are sometimes in ophitic relation to 

 pseudomorphs after pyroxene. The original pryoxene phenocrysts 

 were small and not abundant, and are now completely uralitised. 

 The groundmass is very hne-grained, sometimes massive, some- 

 times Avith a strongly marked flow-structure, in which there are 

 small string-like accumulations of magnetite. The constituent 

 minerals of the groundmass are minute laths of clear felspar, 

 ami3hibolitised and chloritised granular pyroxene, and magnetite. 

 Epidote occurs with quartz in the vesicles, which are often abun- 

 dant. Secondary silicification sometimes has replaced more or less 

 of the telspar-phenocrysts (as in 1138), and veins of quartz may 

 traverse the rock. Small accumulations of dusty haematite are not 

 uncommon. The rock of Pullman's Hill, 48 Nemingha, is quite 

 similar to the above, showing a good flow-structure (1130). Its 

 chemical composition is given on p. 602; the composition of the fel- 

 spar calculated from thisanal3'sis is Or^ Ab^, g Aii^yjOrAb^j^Ang^, 

 which is rather more basic than the composition determined by 

 optical measurements. This discrepancy, no doubt, arises from the 

 presence of chlorite and epidote in the base. The spilite in the 

 eastern side of Portion 65, Nemingha, is similar to the above 

 (1150), so much so that there can be no doubt that it is really a 

 portion of the same rock-mass separated from the Tintinhull and 

 Pullman's Hill spilites by folding and faulting. As remarked, the 

 structure of these rocks is very similar to that shown by the por- 

 phyritic spilites in the Eastern Series in the Nundle District, and 

 is sufficiently illustrated by the photomicrograjDh already given of 

 that rock. (See (17), Plate xxv., fig.3). 



Associated with these rocks, and apparently passing into them, 

 is a less flnely granular albitic rock, which shows the typical sub- 

 variolitic spilite-texture, and has finely crystalline margins about 

 quartz-filled vesicles. Its pyroxene has now been completely urali- 

 tised (1166). The albite-dolerite already described (1024) is m 

 similar association with the spilites at Tintinhull. 



The porphyritic spilites of East Gap Hill have the same minera- 

 logical features as those of Tintinhull, but differ in grain 



