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



sheared, and is composed of light and dark carbonate-grains, with 

 numerous cross-veinlets. The talc and carbonates are very 

 irregularly distributed, and the former presence of chrysolite- 

 veins is occasionally indicated. The distribution of the magnetite 

 is typically that of a sheared serpentine-rock. Sometimes the 

 rock is silicified by the development of chalcedonic veins. 



The rocks on Eumur Creek, Crow Mountain, 20 miles south- 

 east of Barraba, are also interesting. They are both massive 

 and schistose. The surface is brown, and the silica-veins are 

 etched out by chemical erosion. On fracture, they are flesh-pink, 

 with carbonate and clear siliceous veins. Small, green patches 

 occur, which prove to be chalcedonic replacements of serpentine, 

 stained with a little green chlorite. They are sometimes very 

 finely granular, but occasionally are quite coarsely grained; the 

 carbonate-mineral (ankerite 1 ?) is quite idiomorphic, and grows 

 out on either side of the shear-lines that anastomose throughout 

 the rock. 



The ore-body of the Trevena Mine mentioned above, should 

 also be described here. It is a creamy-white rock, sometimes 

 quite friable, with a glistening appearance suggesting a decom- 

 posed, fine-grained greisen (and it is locally termed greisen). It 

 is full of large and small cubical pyrites. Microscopically, it 

 varies somewhat in character. One specimen consists of radiate 

 spherulites of talc, 1 mm. in diameter, dotted with small apatite- 

 crystals and well-developed, sagenitic webs of rutile. The pyrites- 

 crystals are in strings, with perfectly formed, minute rhombs of 

 siderite deeply stained by the separation of haematite. In other 

 examples, e.g., N.T., 504, the talc is in little flakes, placed in such 

 a manner as to suggest derivation from antigorite. There is a 

 little brownish, almost isotropic, matrix, chiefly chalcedony; and 

 into this, the talc-plates cut sharply, rather in the dagger-like 

 manner of antigorite. A little quartz is present, with pyrites 

 and sagenite. Some rocks are very siliceous [e.g., N.T., 499], con- 

 sisting of quartz with very undulose extinction, talc with pyrites, 

 carbonate, etc. The foot wall of the ore-body [N.T., 492], is a 

 green and grey mottled rock, consisting of finely divided talc, 

 with an antigorite (pseudo-gitter) arrangement. It is dotted 



