104 On the Occurrence of the Diamond near Mudgee. 



hitherto stood in the way of the successful investment of capital 

 in this direction. 



The Newer Pliocene drift has afforded a few diamonds. Its 

 materials appear to have been partly derived from the older drift. 

 In one spot, where it rests on greenstone, it consists of a pure white 

 clay, in which gemstones are concentrated in the most remarkable 

 abundance. It is studded throughout with black grains of 

 pleonast, and more sparingly with sapphire, ruby, &c. The 

 accumulations looks like the result of some natural washing 

 process upon the materials of the Older Pliocene, so that it is 

 not surprising that a few diamonds have been discovered in it. 

 In the Newer Pliocene we find Carboniferous conglomerates, 

 pebbles of quartzite containing Spirifer, others of shale retaining 

 impressions of Grlossopteris, rolled silicified fragments of Pavosites 

 and other corals, pebbles of sandstone with crinoidal stems and 

 Orthis, silicified wood, abundance of pebbles of flesh-coloured 

 quartz, boulders of basalt and greenstone — all occurring in 

 addition to the ordinary contents of the older deposit. It also 

 affords the same gems and minerals, and, besides these, a few 

 grains of osmiridmm have been found. 



The recent deposits in the present river channel are of local 

 origin, being derived from the neighbouring rocks, including 

 slates, sandstones, quartz of all kinds, greenstones, characteristic 

 conglomerates from the carboniferous rocks, and silicified fossil 

 wood. The minerals comprise gold, black titauiferous and 

 magnetic iron sand, sapphire, topaz, zircon, stream tin, and brown 

 garnets crystallised in minute rhombic dodecahedrons with edges 

 either entire or truncated. Similar garnets are found in the bed 

 of Lawson's Creek, a tributary which joins the Cudgegong at 

 Mudgee. 



The plan which is adopted in washing for diamonds is — first to 

 screen the drift to separate the larger stones, then to rid it of 

 clay as much as possible in a "torn;" the coarser portions are 

 raked aside, whilst the gold and finer matter is carried by a 

 stream of water through the grating of the " tom," on to the 

 blanket boxes below, where the gold, and occasionally a diamond, 

 is deposited. From the material which passes over the blankets, 

 the heavier fragments are separated from the lighter by various 

 contrivances, among which Hunt's ore-separating machine is the 

 most in use. The heavier stones accumulate in the machine, 

 whilst the specifically lighter materials are washed away, In the 

 heavier portion, thus reduced to a small bulk, the diamonds can 

 be readily distinguished. 



In speculating as to the original source of the diamonds in this 

 locality, many diflBculties arise. Considering that we have not 

 yet discovered the matrix of the pleonast, corundum, zircon, and 

 topaz, which exist in such profusion, it is hopeless to advance any 



