192 ON THE GEOLOGY AND PETROGRAPHY OF BATHURST, N.S.W., 



Calcareous Bocks. 

 Limestones. — Chemical composition, carbonate of lime. Some 

 of the crystalline limestones, of a clear white colour, from Cow 

 Flat, are good examples of this rock. At the limekilns, some 18 

 miles north of Bathurst, there are very considerable beds of lime- 

 stone. Some are white, but, in most instances, they are blue or 

 grey, from the fact that the last remnants of organic life have not 

 been destroyed. 



Altered Rocks. 



1. Hornfels. — A black or bluish-black rock, close-grained and 

 heavy, with blebs of a milk-blue quartz. In hand specimens this 

 rock might be taken for a fine-grained gneiss or an altered schist. 

 Study of the rock, in situ, shows it in every variety, from 

 massive and holo-crystalline to schistose. 



2. Nodular Schist (Knotenschiefer). — Schists in which small, 

 rounded concretions are present, and which stand out like knots 

 on the planes of foliation. Splendid examples of this rock may 

 be found in a creek by the roadside on the Bathurst- Peel Road. 

 The exact locality is at a point where a small bridge or culvert on 

 the main road crosses a tributary of the Winburndale Creek, near 

 the foot of a steep hill, about 7 miles from Bathurst. 



3. Schistose Rocks. — The schistose rocks about Bathurst might 

 be described as clay-slates in which layers of mica have been 

 developed and exhibiting distinct foliation. A typical mica schist 

 is an aggregate of quartz and mica only. Hand specimens can be 

 found about Bathurst that cannot readily be distinguished from 

 typical mica schists. But, as a rule, the rocks that I have noticed 

 might be described as felspathic, mica schists, in fact a transition 

 rock, or a variety between the normal type and a gneissic schist. 

 They are abundantly developed about Cow Flat and in the country 

 round the upper Winburndale Rivulet to the north-west of 

 Bathurst. 



viii. Sedimentary Formations. 



Upper Silurian. — The slates, gneissic schists, and limestones 

 near Bathurst, have been regarded by all our geologists as of 



