702 GREAT SERPENTINE BELT OF NEW SOUTH WALES, Hi., 



on weathered surfaces, white felspar-laths can be distinguished. 

 Microscopically, the augites are seen to be strongly zoned, purplish 

 and weakly pleochroic in the centre, greyish-green in the outer- 

 most portion. The outer zone is usually full of irregular cavities, 

 probably originally filled with liquid, while fragments of felspar, 

 olivine and magnetite are also present. Numerous small pheno- 

 crysts of olivine occur and well shaped cubes of magnetite. Occa- 

 sionally, there are long black rods composed chiefly of minute mag- 

 netite-crystals, which are, possibly, decomposed crystals of horn- 

 blende. The ground-mass consists essentially of plagioclase, sanidine 

 and nepheline, the last being very abundant. The plagioclase 

 varies considerably in amount. In N.T., 414, though subordinate, 

 it is present in notable amount, and has the composition of sani- 

 dine ; but in another example, N.T., 418, very little is present, and 

 sanidine is more abundant. In addition, there are numerous, small 

 prisms of augite and apatite, magnetite and chlorite forming, with 

 sanidine microlites, small aggregates interstitial in the base of the 

 rock. In some rocks, more or less natrolite is present, forming 

 small, dusty patches. The rock, which is clearly to be classed as a 

 nepheline-basanite, may pass into a nepheline-basalt, when the 

 plagioclase is not developed. The chemical composition of N.T., 

 418, is given in Table iii. 



The coarse-grained dolerites of the Peel River gravels have been 

 further studied, and their description, as originally given, is here 

 slightly modified. They consist of large, purple phenocrysts of 

 augite, sometimes half an inch in diameter, strongly pleochroic, 

 and not infrequently containing laths of plagioclase, and olivine- 

 grains. Olivine-phenocrysts occur also, smaller, and subordinate 

 to the augite. Ilmenite is abundant, and apatite is present in small 

 amount. Green aegyrine-augite, of the second generation, forms in 

 the base, in small but long, ragged prisms. The felspar forms 

 irregular tabulae, and is andesine. Interstitially, there are masses 

 of chlorite-stained analcite and natrolite, associated with minute 

 laths of sanidine, apatite, and green augite. The mineral, here 

 stated to be analcite, is the brown, platy mineral of zeolitic nature, 

 mentioned in the Preliminary Note. The dolerites have, then, 



