220 REV. J. MILNE CURRAN. 



Slice 80. — Quartzite from Coronga Peak, Central New South 

 Wales. Coronga Peak is the highest point of all that stretch of 

 •country between the Lachlan and Darling Rivers west of Long. 

 148°. From a distance this hill, which forms a notable feature in 

 the landscape, has all the appearance of a volcanic cone. From 

 more than one point of view it presents splendid symmetrical 

 slopes. On examination, however, it proves to be a hill of 

 Devonian quartzite. Under the microscope the quartz can be 

 •distinguished as primary and secondary — the secondary quartz 

 acting as a cementing material between the original grains. 

 From an examination of the latter, I would conclude that the 

 material which went to build up these quartzites was derived 

 from the denudation of a granitic area. 



Slice 81. — Quartz-porphyry, from Langtree's, Nyngan and Cobar 

 Road, New South Wales. Under the microscope it is seen to 

 consist of corroded quartz crystals and broken felspars in a 

 greatly altered felsitic base. The alteration of the base has 

 given rise to a structure resembling, in minature, the globular 

 weathering of some basalts. I have reason to think that this 

 rock occurs extensively developed for a long distance south of 

 the point whence my specimens were taken. 



Although Tertiary volcanic rocks are developed over extensive 

 areas on the western slopes of the Dividing Range in New South 

 Wales, acidic and even intermediate lavas are by no means 

 plentiful. In the Bathurst and Orange Districts, acidic lavas of 

 Tertiary age are found on the Canoblas Mountain and over a 

 considerable extent of country around the junction of Rocky 

 Bridge Creek with the Lachlan River. These are the only 

 instances known to me in the western slopes of the Dividing 

 Range in this Colony. 



Slice 82. — Trachytic lava, from the junction of Rocky Bridge 

 Creek, Lachlan River. The cavities of this rock are filled with 

 opals, many of which are splendid examples of fire opal. The 

 rock has evidently been subjected to hydro thermal influences that 

 have altered it considerably. Under the microscope it will be 



