584 GREAT SERPENTINE BELT OF NEW SOUTH WALES, ii., 



(1) Hydration has taken place, to a greater or less extent, 

 throughout the whole mass ; very little olivine remains unattacked. 

 We, therefore, get normal, massive, bastite-serpentines, schistose 

 serpentine, and antigorite-serpentine, the latter being best de- 

 veloped on the Razorback Ridge, half-way up Munro's Creek, 

 where some of its features resemble Weinschenk's stubachite(31). 



(2) Carbonation is developed best between Folly Creek and 

 Quackanacka Creek, and is well exposed in the workings of the 

 Trevena gold-mine. The rock is more or less completely converted 

 into carbonates of magnesia and iron, with a little talc, quartz, 

 chalcedony, etc. With this is associated more or less pyrites. Both 

 the schistose and massive types of serpentine have been thus 

 altered, and their original structures are well preserved. The rock 

 does not make a strong outcrop, but, on the surface, is weathered 

 to a cavernous, red haematite, with a little talc, by which the forma- 

 tion may be traced. In the western side of the serpentine, the 

 Bowling Alley rocks have been acted upon by the same agents as 

 transformed the serpentine. Clayshales, spilites, and tuffs occur 

 highly oxidised and carbonated, and impregnated with pyrites. 

 This entire formation is more or less auriferous, but differs entirely 

 from any other gold-bearing formation in the district. 



(3)Silicification takes the form of replacement of the serpentine 

 by chalcedony, quartz, and opal. The change occurs in various 

 ways, and frequently is associated with leaching. In Sheep Station 

 Creek, the serpentine contains little cavities lined with chalcedony, 

 and the main mass of the rock is partly replaced by silica, as 

 chalcedony and white opal. On Cope's Creek, and to the east of 

 Chrome Hill, is a narrow band of serpentine, changed chiefly to 

 very finely divided chalcedony, with the preservation of the schis- 

 tose structure of the original rock. ^Between Munro's Creek and 

 Folly Creek, the serpentine is replaced by a bottle-green opal with 

 black cloudy masses (pyrolusite). This opal forms kernels sur- 

 rounded by a husk of haematite, veined with white opal, and 

 speckled with dusty talc or hydromagnesite. By Hanging Rock, 

 at the head of Oakenville Creek, on the east side of the serpentine, 

 is a large mass of silicified rock, from which excellent specimens of 



