410 Norman Taylor — The Cudgegong Diamond Field. 



mineral occurs, probably a clay coloured by silicate of iron. The 

 basalt is magnetic, with strong polarity in places, and the water 

 channels draining off it contain a fine black magnetic iron sand. 

 The columnar structure above noticed renders shaft sinking in these 

 basalt hills tolerably easy. From the peculiar position, with regard 

 to one another, of these basaltic outliers, and the apparent impos- 

 sibility of drifts of such varying thickness being part of the same 

 river-bed (I now allude to the older drift), I at first supposed that 

 " the flat" had once been a lake, subsequently drained by the river 

 cutting through the greenstone dyke ; but, on taking a series of 

 barometrical levels across the flats, in and across the strike of the 

 rocks, with accurate measurements of shafts sunk, etc., this suppo- 

 sition proved erroneous ; for the drift-bottom is higher at Buckley's, 

 on the east, than at Driscoll's, on the west side of " the flat " or fall 

 of the river, although Buckley's has suffered more from denudation, 

 and is consequently lower than the other hills. During the forma- 

 tion of the newer drift it may, however, have been temporarily a 

 lake. The " Deep lead " is a curious feature, for, at Fitzpatrick's 

 Claim, the older drift-bottom is nearly 20 feet below what it should 

 be in the average fall of the river, and is nearly on a level with the 

 newer drift, and a very little above the present river-level. It is 

 evidently older drift, inasmuch as it underlies the basalt, — and the 

 only way to account for it is, that it must have been a large and 

 deep waterhole. 



The centre of the north end of the flat is occupied by a mass of 

 greenstone, apparently intrusive. According to the late Professor 

 Thomson, some of the greenstone of the Wellington district is con- 

 temporaneous, and interbedded with the Upper Silurian rocks ; but, 

 in one place here, we have it cropping out on both sides of a sand- 

 stone hill, but not appearing at the top ; and, in another place, the 

 greenstone is capped by a mass of altered shales, similar to what 

 occurs at Lancefield in Victoria, where a high greenstone range is 

 capped, in patches, with undenuded outliers of altered flinty shales. 

 Its occurrence in parallel bands, having the same strike as the adja- 

 cent vertical and highly-metamorphosed shales, seems to favour the 

 view of its being interbedded, as also does the presence of what 

 may possibly be trappean ash-beds (described further on). I think, 

 however, that, were there any good sections across the strike ex- 

 posing these rocks, it would be found that the Upper Silurian rocks 

 are here underlaid by a large mass of greenstone, which throws up 

 veins through the joints of the slates and sandstones. The green- 

 stone (diorite) consists of a mixture of hornblende and felspar, and 

 varies from a fine-grained extremely hard and tough compact rock 

 to a coarsely crystalline one. Its colour is a dark green, and in 

 weathering it forms a rich red soil. It exhibits a concretionary 

 structure at the surface, but is very dense below. In places it is 

 largely intersected by epidotic veins of a light chrome green colour, 

 containing, occasionally, rhombic prisms of epidote ; it is also cha- 

 racterized by the presence of quartz, sometimes containing confusedly 

 radiating olive-green prisms of actinolite. The felspar crystals have 



