BY SYDNEY B. J. SKERTCHLY. XXlll 



following the system of faults. Some of them are of great rich- 

 ness, and, as in the case of the North Australian Tin and Copper 

 Mine, at Watsonville, and the Vulcan Tin Mine, at Irvinebank,. 

 huge masses of almost pure ore worth many thousands of pounds^ 

 have occured and are likely to occur again. 



(5). Beihh'd or ('Iciirai/t' Ih'jxj.sits. — ^These are similar to the 

 above, but bedding or cleavage planes, being the lines of least 

 resistance, have proved the channels for the introduction of the 

 ore which has impregnated the adjacent country. 



These are always indefinite and unreliable, and though they 

 occur in our district none are of sufficient importance for com- 

 mercial purposes. 



(6). ( '« re Deposits. — As might be expected, it has occasionally 

 happened that copper has been carried by underground drainage 

 into caves, and there been deposited as ore. This can be seen 

 on a small scale near the Harper Mine, and on a large scale in 

 the Griffith Mine at Mungana. 



(V.) Lhimanics of tlic Ih'posits. — The geological history of the 

 district repeats in a more complicated manner the story I have 

 worked out for the mineral region of South Queensland. 



We start with a rugged mountainous country formed of the 

 Silurian rocks, which had already been metamorphosed into 

 schists and gneiss, and which we now call the Dargalong Beds. 



Then came a long period of depression beneath the sea, 

 probably in Lower Carboniferous times, during which the 

 Herberton beds were laid down. Fragments of the old shingle 

 becich still remain in the Eingrose Conglomerates. This was 

 followed by a gradual elevation, which to some extent upturned 

 the Herberton beds. The new land was sculptured into hill and 

 vale by the denuding action of rain and rivers. 



A repetition of this process laid down the ^lontalbion Beds. 



Then, towards the close of the Carboniferous period, ensued 

 another depression, during which the Chillagoe Limestone was 

 laid down on the worn edges of the Herberton beds. 



Up to this time little or no mineral deposit had been formed. 

 During the ensuing Permian period a total change occurred. 

 The gi-anite slowly " Wrought its skyward impulse from Earth's 



