Norman Taylor — The Cudgegong Diamond Field. 449 



and late colleague, Mr. C. S. Wilkinson (Mines and Mineral Statistics 

 of New South Wales, 1875, p. 77, et seq.), on the Tin-mines of New- 

 South Wales, that the older diamond drifts must be of the same 

 age as the older Tin "leads" of Borah Creek, which also contain 

 diamonds. 1 



In ascending order, commencing with the oldest, they would pro- 

 bably occur as follows : — 



1. Upper Miocene, or ) Older Drift, possibly fluvio-marine, underlying basalt, 



Lower Pliocene, j and containing gold, tin, and gems — no fossils to prove 

 age. This drift may again be sub-divided into two — one containing 

 semi-angular quartz (a reef wash), and the other rounded boulders. 2 



Lapse of time, during which were formed— 



2. Middle Pliocene. — The Gulgong deep leads with plant-remains, the latter 



described by Baron von Mueller. These leads perhaps drain into an 

 old lake-basin at the head of Reedy Creek. 



3. Basaltic overflow, filling lake and flowing down the Cudgegong Valley. 



4. Wash of conglomerate pebbles, etc., over the surface of the basalt. 



5. Upper Pliocene. — Newer Drift, fluviatile, and derived from all the above 



during the cutting out of a new river channel. To this or the next 

 division may belong the " leads," higher up the river, containing fossil 

 bones at the Pipeclay Diggings, and cinnabar near the village of 

 Cudgegong. 3 



6. Pleistocene. — The older river channels, now silted up, and below the level of 



the present river-bed. 



7. Pv,ecent. — The present river-bed. 



With regard to these older drifts, it must be borne in mind that 

 they vary much in position ; they are below the river-bed at the 

 Eeedy Creek, and much above it at the Two-mile-flat, the present 

 river falling at a greater rate than the old river. 



The older diamond-bearing drift, underlying the basalt, is a coarse 

 and heavy deposit, — some boulders in it weighing several hundred 

 weights, — for the most part loose, but portions of it united into a 

 compact conglomerate. It varies greatly in thickness, from a few 

 inches to 30 feet, according to the irregularities, in some cases, of 

 its own upper surface, which is not uniformly level ; and in other 

 cases, due to the old river-bed. Huge blocks of hard slate, sand- 

 stone, quartz, greenstone, and felspathic rock, the two latter often 

 decomposed into masses of clay, still retaining the original shape of 

 the boulders, lie at the base of the drift in many parts. 



The following are the contents of this drift, which is, however, 

 very variable in different localities : large and small boulders and 

 pebbles of quartz, generally coloured a reddish-yellow or brown 

 externally by oxide of iron ; sand of various degrees of fineness ; 

 pebbles and sand cemented by oxides of iron and manganese, or by 

 both together, the iron coating the quartz in concentric rings, and 



1 These are considered by Mr. Wilkinson to be of Miocene age. — E. E , jun. 



2 At the time of the formation of the older drift, the Carboniferous rocks to the 

 east and south-east may have been above the reach of marine action, and so escaped 

 the denudation ; thus accounting for the absence of any traces of them in the drift. 

 The denudation of the Carboniferous rocks may have commenced after the basaltic 

 outbursts, and during the cutting out of the new river valley. 



3 At the Cudgegong cinnabar mine, boulders of coal and sandstone occur in the 

 drifts, with large sapphires and zircons, but no diamonds or topazes, nor did I find 

 ruby, though it is stated to occur there. 



decade ii.— vol. vi. — no. x. 29 



