62 Notes on the Geology of the Country around Goullum. 



are commonly opaque, homogeneous in their texture, white, or 

 tinted dull blue, brown, olive, yellow, or red ; they appear to 

 consist of mixtures of clay and silica. They occur in persistent 

 layers of a few inches thickness, interbedded, with the other 

 stratified rocks. 



The altered shales, slates, and schists are represented by the 

 specimens shown ; the two former kinds of rock are invariably 

 fine grained, and are of argillaceous origin ; but the schists, 

 though generally fine grained, are sometimes coarse. The varie- 

 ties of schist observed in the county might be distinguished as 

 chlorite schist, mica schist, quartzite schist, and quartziferous 

 schist. By quartziferous schist, I mean such as the specimen 

 shown containing small lumps of quartz disseminated between 

 the fine-grained schistose layers. This rock is certainly inter- 

 mediate in structure and appearance between an ordinary schist 

 and the quartz porphyry, to be referred to immediately ; and in 

 a small spot, near Lake George, laid down upon the map it was 

 traceable passing gradually into quartz porphyry. It is probable 

 that it is a transition stage between the actual transmutation of a 

 schistose rock into quartz porphyry. 



The quartzose and slaty rocks just described form a barren 

 soil, except in the spots where they happen to be covered by 

 alluvium. Most of the ridges are stony, and the vegetation, 

 instead of protecting the rocks from waste, as usual, often causes 

 disintegration, for the roots of the trees, penetrate between the 

 thin layers of the highly-inclined beds and break them to pieces. 



Along with these remarks relating to the stratified arenaceous 

 and argillaceous materials, it is natural to mention the interstra- 

 tified calcareous members of the series, indicated on the map by 

 blue. The limestone in the county of Argyle is generally of a 

 light blue tint, very hard and brittle. Like the sands and the 

 clays, the limestone has also had its share of geological vicissi- 

 tudes, and is now hard and crystalline. On the Wollondilly at 

 Long Reach there is an outcrop of a highly inclined bed of 

 cream coloured marble with faint red mottling, but it breaks in 

 a splintery manner. Eastward of Aiarulan, towards the Shoal- 

 haven River, a pure white marble with rather a coarse grain is 

 found. And on ^Yindellama Creek, there occurs a black marble 

 with a few white fossil markings, lying in slabs from three inches 

 up to a foot or two in thickness. 



The limestones are fossililerous, but it is very rare to meet with 

 fossils in the other stratified rocks alluded to ; still, the fact of 

 the fossils being well preserved in the few instances where they 

 do occur points to the conclusion that the unfossiliferous sedi- 

 ments were originally devoid of fossils, and that the absence of 

 fossils in them cannot be attributed to obliteration resulting from 

 the changes which the rocks have undergone. 



