0)1 the Occurrence of tJie Diamond near Mud^ee. 95 



As far as at present known, the localities on the Cudgegong 

 ■which produce diamonds lie along the river, extending from its 

 junction with Wialdra Creek (eighteen miles IN". 30° W. of 

 Mudgee), to a point further down seven miles S. W., known as 

 Hassall's Hill. Along this line the distribution of the diamond 

 is by no means general, but is confined principally to a few small 

 outliers of an ancient river-drift, which occur at various distances 

 from the present channel, and at elevations of 40 feet or so above 

 it. These outliers of drift are capped by hard, compact, and in 

 many instances, columnar basalt ; they have all the characters 

 of the wide-spread deposits in Victoria, which the Geological 

 survey there has been accustomed to assign to Older Pliocene. 

 They also agree with, it in occurring underneath a basaltic rock, 

 which presents, in Mr. Taylor's opinion, the characters of the 

 Older Pliocene basaltic flows, such as are extremely common in 

 Victoria. At present there is no direct fossil evidence from the 

 diamond drift itself to assist in the determination of its exact 

 age. Portions of a humerus and a molar tooth, the latter rather 

 too much shattered to identify with certainty, but sufficiently 

 distinct to show that it belonged to some huge herbivorous 

 marsupial larger than anything living now, have been found in 

 younger drift higher up the river, at Magpie Grully, near the 

 G-ulgong Diggings. 



The patches of diamond-bearing drift (Older Pliocene) with 

 their protective coverings of basalt, though once forming parts of 

 a continuous deposit, have been isolated by extensive denudation. 

 The point of eruption from which the basaltic flow emanated 

 appears to lie to the eastward, but it has not hitherto been 

 detected ; its remnants can be followed up for at least seventeen 

 miles along the river, in some spots still showing a thickness of 

 seventy feet, which proves the igneous outburst to have been of 

 considerable magnitude, sufficient to materially alter the physical 

 aspects of the river valley ; Ave may also infer, conversely, the 

 enormous extent of the subsequent denudation. There is the 

 clearest local evidence that the course of the river has been much 

 altered since the older drift formed a portion of the channel. 



Enumerating in descending order the outliers of this Older 

 Pliocene drift which afi'ords the diamond, the first area occurs at 

 the starting point, the junction of Eeedy or Wialdra Creek with 

 the Cudgegong. The dimensions of this area cannot be fairly 

 estimated, as much of the basalt has been covered up by various 

 surface accumulations ; it lies partly on private ground, and has 

 been insufficiently explored. 100 acres might be taken as an 

 estimate of the extent of the workings as far as yet developed. 



2. Jordan's Hill. — Three miles below, on the left bank, a 

 triangular basaltic area of about 40 acres. 



