Mount Morgan Gold Mine. 343 



In the deeper levels of the mine the walls are in an unaltered 

 condition, and appear to be of fine grained diorite. In one 

 case such rock was thickly studded with scales of native copper. 



Up to the present no microscopical examination of the ex- 

 tremely interestinu" gi-oup of rocks around Mt. Morgan appears 

 to have been made. 



Structure. 



As sho^vn on the accompanying plan and section, the top of 

 Mt. Morgan is occupied by a plug three-fifths of an acre in 

 extent of sandstone (A). This sandstone was evidently an outlier 

 from the Desert Sandstone of Dr. Jack, which is so well I'epresented 

 a few chains to the north-west, capping the range. Tlie plug was 

 doubtless at one time continuous with the main mass, and its 

 isolation was due to denuding agencies which have also pared 

 it down to the condition it was in before removal by mining 

 operations. The sandstone was moderately coarse-grained, red 

 in colour at the surface, but nearly white in parts lower doAVTi. 

 It was bedded horizontally in beds from a few inches to a couple 

 of feet thick, and extensively false bedded. The mass formed 

 an inverted flattened cone, and filled the inside of the funnel- 

 shaped mass of sandy beds of secondary ore (B on plan and 

 section). Assays of this sandstone gave up to 3dwt. of gold pei 

 ton, and this is not remarkable, seeing that the walls of the 

 cavity in which it was laid down were highly auriferous. The 

 whole of this plug, which was nearly 100 feet deep at its 

 thickest part, was quarried and tipped over the side of the 

 Mount, so as to remove the rich secondary ore below it. It 

 was quite distinct from, and unconformable to, the beds of loose 

 sand, etc., underlying it. By means of this outlier of desert 

 sandstone it is clearly established that the secondary ore was 

 laid down before the Desert Sandstone began to be deposited, 

 though probably not long before. From the degraded condition 

 of the plug it is certain that denudation had removed a portion 

 of the secondary ore around the plug, but there was not any 

 means of gauging the extent of this work. Formerly a black- 

 smith's shop stood on the plug of sandstone. 



Surrounding the plug of sandstone were beds of loose sand, 

 etc., very irregularly bedded and disposed somewhat after the 

 form of a rim of a funnel (B on plan). Towards the centre the 



