AUSTRALIAN MINING-FIELDS 



123 



have been limonite and not anhydrous oxide of iron. It is 

 probably an ore deposit due to the interaction between water 

 percolating through the conglomerate and ascending ferruginous 

 solutions along the fault plane. 



The North Lyell Mine has been described by Mr. W. T. 

 Batchelor, 1 the engineer in charge of mining operations at 

 Mount Lyell. The mine is situated in a mass of schists, which 

 has been intensely crushed and contorted, by having been faulted 

 between blocks of the hard conglomerates. The ores are siliceous, 

 and consist of quartz and broken schist charged with chalco- 

 pyrite, bornite, and chalcocite. The average of the ore that 

 pays to extract under present conditions has been brought 

 down as low as 6*25 per cent, of copper ; but in places there 



Fig. 2. — Diagrammatic Section through the Mount Bischoff Mine. 

 c.s. Contorted Silurian. p. Porphyrite. f. Fault. 



s. Silurian. 



q. Queen Lode. b.f. Brown Face. 



are rich veins of almost pure bornite, which are in places 

 2 ft. in thickness ; they follow the strike of the schists. 

 The bulk of the ore is in masses, of which about eight were 

 known in March 1904. One of them, the " Eastern Ore Body,' 

 is a brecciated mass of quartzite and schist, occurring between 

 the main conglomerate mass of Mount Lyell and a faulted 

 conglomerate outlier to the west. The genesis of the ores is 

 doubtless similar to that of the Mount Lyell Mine; but the 

 ore masses are more irregular, owing to the more intense 

 disturbance of the rocks by the more intricate nature of the 

 faulting; and they will probably continue to greater depths. 



1 Op. cit. pp. 108-16. 



