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



The other massive serpentine is more purely raagnesian, 

 weathers to a fairly smooth surface, and whitens by change to 

 talc, which mineral also forms small veins rarely. Frequently, 

 the rocks show green and cream-coloured patterns, in varying 

 shades, of great beauty, reminding one of "alligator-skin" leather. 

 Rarely they are reddish, and, in one instance, the rock is vesicular 

 [N.T., 218]. Some constituent has been removed, leaving very 

 irregular cavities, but what that mineral was, is not at all obvious. 

 On fracture, the rock shows a fairly smooth, sometimes oily, green 

 surface flecked by bastite-crystals. 



The least altered rock [N.T , 388] occurs in the lower portion 

 of Munro's Creek. It is chiefly yellowish serpentine, with very 

 numerous olivine-residuals in its meshes. The pyroxene is 

 diallage, which has a poikilitic structure. It is but slightly 

 altered, the serpentine growing out from its cleavages, or inwards 

 from its outer margin. The presence of the monoclinic pyroxene 

 makes this rock one of the few lherzolites yet observed in the 

 area. Chromite is present in only small amount, but white, 

 cloudy masses of steatite are not infrequent. 



The effect of pressure is first marked by the production of an 

 undulose extinction in the bastite, and the development of 

 chrysolite-veins throughout the rock. In these, further move- 

 ment shears the fibres, breaking them into frayed wisps; small 

 veins are formed, traversing the olivine and bastite serpentine, 

 filled by fibres and plates crossing them perpendicularly, and 

 these later become sheared out of position. The movements 

 naturally tend to take place along the major mesh-lines of the 

 original serpentinisation, which are marked by the presence of 

 long strings of magnetite. In such rocks, the original enstatite 

 may be represented by only an oval patch, with a slightly less 

 sheared structure, and a greater freedom from bastite than the 

 rest of the rock. Ultimately even this distinction is lost. 



A few examples may be specially noted. The serpentine, in 

 the highly displaced rocks of Gulf Creek Mine, shows shearing 

 developed to its greatest degree. The lenticle is apparently 

 fairly narrow. Its best exposure is in the Mine- workings, for it 

 is scarcely seen on the surface; and it seems quite impossible, 



