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II.—On the Cudgegong Diamond Field, New South Wales1
Published online by Cambridge University Press: 01 May 2009
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The next appearance of the older lead is at the “Rocky-ridge,” where the river, after running northerly for three-quarters of a mile, along the strike of the metamorphic beds, turns abruptly to the west. This ridge is a basalt-capped hill on the north side of the river, running in a north-west direction; it is about a mile long, with a bold rocky escarpment on its west side, facing the Sandy or Cudgebeyong Creek. Some tunnels have been driven in, and shafts sunk on this hill, and tolerably rich deposits of gold were found, but never followed out.Only in the southern half of the hill have diamonds been found(all more or less spotted).The drift is remark-able for the number and size of the agates it contains.The northern half of “the ridge” is underlaid by another outlier of the before-mentioned doubtful purple conglomerate, into which some tunnels have been driven in the western escarpment.The basalt is merely a fringe here, resting against the flank of the conglomerate, in which a small quantity of nuggetty gold was obtained;and form one to two inches thickness of lignite, or carbonaceous clay, is seen between it and the bottom of the basalt. Tte basali is intersected by numerous veins of a mineral allied to kaolin. The purple con-glomerate is similar in character to that near “the flat”and contains, on some of the joint faces, smll spherical crystalline aggreations of chalybite(carbonate of iron).At the extreme north ead of “the ridge”are great quantities of ironstone and conglomerate, but, from their Carbpniferous series, which is largely developed further north.The first diamonds which found their way to Melbourne were obtained.
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References
page 449 note 1 These are considered by Mr. Wilkinson to be of Miocene age.—R. E., jun.
page 449 note 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.
page 449 note 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.
page 451 note 1 The pebbles from these cements have sometimes a very peculiar resinous glaze on their surfaces, which is certainly not due to friction, as the cavities are equally glazed as the exposed surfaces. It is probably siliceous
page 455 note 1 See also, Liversidge, Quart. Journ. Geol. Soc. 1875, vol. xxxi. pp. 489–492.—E. E., jun.
page 457 note 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.
page 458 note 1 See Trans. R. Soc. N. S. “Wales for 1870, pp. 1–48, “ On the Discovery of the Diamond in N. S. Wales;” and Ibid, for 1872, pp. 1–66, “ On the Natural History of the Diamond.”—E. E., jun.