144 GREAT SERPENTINE BELT OP NEW SOUTH WALES, iv., 



crystals of augite occur, which are like rods made up of very 

 minute grains, and feathered, one might say, with tiny plates of 

 ilmenite. Such minutely granular augite is also frequently 

 around minute laths of plagioclase. In many of these rocks 

 there is more or less brown glass in the base (see Plate xxv., fig. 6). 

 The spilites are frequently vesicular, and sometimes, in the holo- 

 crystalline spilites, the vesicles are surrounded by hypocrystalline 

 rock. One of the most remarkable types of rock is that in which 

 an ophitic dolerite of medium grainsize has interstitial areas of 

 fine-grained subvariolitic rock (Plate xxv., fig.2). 



The amygdaloidal dolerite and holocrystalline spilites described 

 above are characteristic of the non-pillowy masses of spilite and 

 the central portions of the pillowy spilites all along the French- 

 man's Spur, and the slopes north of Tom Tiger. The outer por- 

 tions differ in being hypocrystalline. The phenocrysts and 

 felspar microlites in the groundmass are sharply bounded, take 

 on more distinctly the clustering radiating habit of variolitic 

 rocks and are surrounded by a blackened border, full of skeleton- 

 ilmenite and finely divided augite. In such rocks, there are fre- 

 quently clear traces of fiow-breeciation, the several fragments 

 being sharply bounded in some places; in others they merge into 

 the surrounding rock. These rocks show many structures within 

 a short space, glassy, fragmental, or variolitic, solid or filled with 

 lakelets of chlorite. In all these the felspars remain quite clear, 

 and are acid oligoclase or albite. The extreme outer margin of 

 one pillow in Swamp Creek exhibits a structure of which no 

 parallel is known to the writer. It so closely resembles the plan 

 of a pillow-lava that it may be termed the micro-ellipsoidal 

 structure. It is probably a first stage in the formation of vario- 

 litic structure, preserved owing to the sudden quenching. The 

 rock is broken up into small ellipsoidal portions about 0-2 mm. in 

 diameter, consisting of radiating fibres of a dark brownish-green 

 colour (chloritised augite ?), surrounded by a ring of clear epidote. 

 This epidote is separated from the epidote in the adjacent 

 micro-ellipsoid by a thin band of grey dusty material, which 

 widens out inco tricuspate areas at the point of contact of three 

 micro-ellipsoids, just as does the material between the large 



