666 GREAT SERPENTINE BELT OF NEW SOUTH WALES, iii., 



tailed extremities, are a very marked feature (Plate vxv., fig. 2), 

 In some of the spilite-fragments included in the Baldwin agglomer- 

 ate, this becomes even better marked. Among these, there are 

 strongly pumiceous types. 



The spilites, that occur east of the serpentine-line, are very abun- 

 dant, and are greatly altered by pressure. Sometimes they have 

 received a schistose structure, with phacoidal cleavage, and, if not 

 vesicular, are easily mistaken for altered sedimentary rocks. An 

 excellent example of these is M.B., 56, from Woods' Reef. This, 

 when seen microscopically, shows that it has been sheared in 

 several directions. Some shear-lines are marked by finely pulver- 

 ised rocks, the adjacent felspar-laths being sometimes dragged out 

 and bent. Crossing these, are numerous carbonate-filled veins, 

 which have been slightly sheared also. 



N.T., 283, is a spilite from Folly Creek, near Nundle, occurring 

 adjacent to the serpentines on Folly Creek, that have been changed 

 to carbonates, and has been affected by the same solutions that 

 altered the serpentine. The ferromagnesian minerals are gone, and 

 much carbonate, talc, and a little pyrites have been introduced, 

 while the rock has been much bleached. 



(2) The keratophyre on Opossum Creek, Hanging Rock, forms a 

 roughly circular area about 30 yards in diameter, and is probably 

 a volcanic plug. It is buff-coloured, fine-grained, with calcite- 

 filled vesicles [N.T., 195]. It is pilotaxitic in texture, composed 

 almost entirely of laths of acid oligoclase. A few magnetite grains 

 occur, but the augite, which occurred interstitially and in small 

 phenocrysts, is completely replaced by chlorite. 



(3) Devonian Dolerites. — These rocks have a medium grain-size, 

 varying from 1-3 mm., in diameter. The texture of the rock is not 

 constant; in one instance only is it gneissic; in the others, it is 

 never more than subophitic, and, more usually, the augite is more 

 prismatic and idiomorphic than the felspar, and is sometimes bent, 

 through movement during consolidation. In these rocks, with both 

 main constituents partially idiomorphic, there are interstitial areas 

 filled in with finely crystallised, lath-like felspar or quartz-grains, 

 or quartz and felspar conjointly. The constituent minerals are 



