350 Proceedings of tlie Royal Sorletij of Vicforia. 



richest spot was about 20 feet north-west from the shaft on No. 

 3 floor. The limonite also in places was phenomenally rich in 

 gold ; some large blocks assayed up to 800 ozs. per ton. Taken 

 as a whole, the secondary ore was a marvellously rich deposit 

 of gold-bearing material. It represented a zone of enrichment, 

 and the gold it contained was derived by the leaching and im- 

 poverishment of an enormous mass of adjacent ore. 



When the great richness of the surface ore at the Mount was 

 proved, prospecting was eagerly pushed on with the object of 

 discovering the continuation in depth, but although the Mount 

 was pierced right through at several points and right beneath 

 where the rich ore stood, no continuation could be discovered 

 belo^v, and the reason is obvious from the plan and section 

 given. For while the workings at the surface were in the 

 enriched zone of secondary' ore the tunnels were driven through 

 the impoverished zone of cellular siliceous rock from which the 

 sulphides and much of the gold had been leached out. 



The secondary ore was, with the exception of the ironstone, 

 in such a loose and friable condition that most of it was re- 

 moved with a shovel. 



It is quite possible that in the secondary ore a certain amount 

 of Desert Sandstone material may have been mingled with the 

 material resulting from the disintegi-ation of the cellular siliceous 

 rock, for the Desert Sandstone sea must have covered this area 

 while the secondary ore was being formed, and that some sand 

 should have been carried in seems quite nattiral. 



Gold. 



In the enriched zone gold existed not only in exceptional 

 abundance, but the quality was abnormally high ; in fact, no 

 naturally-formed gold is known that more nearly reached 

 chemical purity than the gold obtained near the surface at 

 Mt. Morgan. Thousands of ounces were bought at the 

 Sydney Mint that w^ei-e 99.7 fine, and some reached 99.8. This 

 unusual degree of fineness was certainly due to the processes by 

 which the much-alloyed gold of the sulphides w^as fu-st dissolved 

 and leached out of its original ore and then re-deposited under 

 such conditions that no silver was deposited at the same time. 



