Norman Taylor — The Cudgegong Diamond Field. 457 



had no fossil evidence. The diamond drift rests on argillaceous 

 shales with interbedded conglomerates. The miners regard these 

 conglomerates as being diamond bearing, but without any proof. 

 He states also that he had not detected any fractured diamonds. 1 



If the diamond is derived from the Carboniferous rocks, why is it 

 not found in the present river-bed (except where tailings have been 

 washed into it) which abounds in Carboniferous detritus ; more 

 than one-half of the pebbles and boulders consisting of Carboniferous 

 conglomerates ? Why also is it totally absent, although carefully 

 looked for, in close proximity to the Carboniferous rocks, as at 

 Cudgegong, and immediately under their escarpments at Tallawang, 

 and in all the streams of the upper sources of the river ? It is rare 

 to find a trace of the Carboniferous rocks in the older drift, and 

 only occasionally in the newer, whilst they are common in the most 

 recent river drifts. The sand in the newer drifts is probably the 

 remains of the Hawkesbury sandstones, which overlie the Carbon- 

 iferous rocks, and must at one time have had a far wider extension. 

 The late Eev. W. B. Clarke observed that the occurrence of grains 

 of graphite in the Hawkesbury rocks looks like an approach towards 

 the diamond ; and, in a letter to the writer, he says that the evidence 

 of fossil wood must be rejected, as it is found in various formations 

 of all ages. 



If the gem-stones in the older drift (underlying basalt) were derived 

 from basalt, this basalt must have been older than that now covering 

 the drift, and there is no trace of such older basalt, if we except that 

 capping Mount Bocoble, west of Cudgegong, which is of a totally 

 different character to the Cudgegong flow, and at nearly 1000 feet 

 higher elevation. We are then driven to the greenstones and 

 granites for the origin of the gems, and here we are completely at 

 fault. 



The Broombee and Cudgegong limestones (Devonian) may have 

 supplied the rubies, as they do not occur above the latter place, nor 

 are topaz or diamond found there. 



The gems associated with diamonds are very common in most of the 

 river drifts of Victoria and New South Wales, but in one instance only 

 in the former colony, at Beechworth, have diamonds been found. 

 And, if these gems are derived from igneous or metamorphic rocks, 

 and their presence is an indication of the diamond, how is it they 

 are associated in one place and not in another, the surrounding cir- 

 cumstances being apparently the same ? 



Why is the corundum family — all the members of which, or nearly 

 all, are as hard as the diamond, and harder than all other rocks which 

 would be at all likely to grind down their angles — rounded and 

 fractured, and not the diamond, which, although the hardest mineral 

 known, is brittle and easily fractured on its cleavage planes ? 



1 The cinnabar erroneously quoted by Professor Liversidge (from the article by 

 the late Professor and the writer) as occurring at the Mudgee diamond field, does 

 not do so. It is found in an old river drift near the village of Cudgegong, over 

 40 miles higher up the river, and has no connexion whatever with the diamond 

 drifts. 



