146 GREAT SKRPENTINE BKLT OF NEW SOUTH WALES, IV., 



The dolerite of the Possum Tunnel and elsewhere, near Bowling 

 Alley Point, has been invaded by a coarse pegmatitic dolerite, 

 consisting of oligoclase-albite (not andesine), augite, and large 

 ilmenite-plates with a little interstitial quartz and plagioclase. 

 The rock is rather crushed, and much veined with quartz, epidote, 

 and calcite. 



The long string of spilite-occurrences, running from north of 

 Tom Tiger to the Oaken ville Creek, have been already described. 

 The spilite first analysed is one of these (117, N.T.415, Part iii , 

 p.704). It has a complex texture; coarse phenocrysts and 

 glomero-porphyritic aggregates occur in a spilitic ground mass 

 in which are vesicles filled with calcite, and surrounded by 

 fine-grained, subvariolitic, hypocrystalline material (see Part iii., 

 Plate xxvii., fig.l). The spilites of Moonlight Hill have a par- 

 tially granular, partially ophitic texture, and pass laterally into 

 fine-grained spilitic masses. No special textural features are to 

 be seen in the dolerite that contains axinite in its vesicles, save 

 in the widely differing character of the material filling adjacent 

 vesicles. Quartz, epidote, chlorite, calcite, and axinite occur 

 singly, or in association. 



A small sill crossing Moonlight and Madden's Creeks exempli- 

 fies best the porphyritic spilites with basaltic groundmass (Plate 

 XX v., fig. 4). Its vesicles contain quartz, which also appears to 

 be replacing the rock metasomatically. Both magnetite and 

 ilmenite occurred, but the latter is now changed to titanomor- 

 phite. The sill, though only four yards wide, is much more 

 finely granular on the margin than within, though there is no 

 alteration in texture or composition. 



The spilitic rocks in the Woolomin Series are not so varied in 

 texture. They are rather basaltic in character, and the pheno- 

 crysts are not very abundant. ]n one instance only has a pillow- 

 like mass been found in the Woolomin rocks of the Nundle dis- 

 trict. The rock of which it was composed consists of a few 

 phenocrysts, clear plagioclase and uralite, set in a base of the 

 same materials. The felspar of the groundmass is fresh, often 

 untwinned, and very fine-grained (PI. xxv., fig.3). Other rocks 

 show the same original structure, but are more crushed. A few 



