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Report on the Geology & Gold Fields of Otago

Chances of Prospecting for Auriferous Reefs

Chances of Prospecting for Auriferous Reefs.

As regards the chances of the occurrence of other auriferous reefs in the districts under notice, [consider them to be very good. In the neighbourhood of Saddle Hill Reef, several (4) good-looking, strong reefs crop out, which, as superficial prospecting has already proved them to be slightly auriferous, might likely yield payable stone on being tried at other points in their lines of strike. But besides this, there is in my opinion a very good chance of the existence of an auriferous reef about the head of a highly auriferous gully, worked abreast of the Saddle Hill Reef, on the right hand side of the main road lead ng from Dunedin to the Taieri. In the neighbourhood of the Canada Reef, Tokomairiro, the finding of rich quartz specimens outside the lines of the reefs opened, coupled with that of rich, nuggety gold in the north branch of the Tokomairiro River, is pretty good evidence of the occurrence of other auriferous reefs in that district. That the Gabriel’s Gully Reef should be the only aur f rous one in the Tuapeka district is also very unlikely. And, touching the country round Waipori where no systematic prospecting seems to have been carried on at all, I feel quite convinced that good reefs exist besides the one in work—not only in the neighborhood of the latter, but also in the ranges on the opposite side of and about the head of the Waipori River,—in order to account for the gold in the drift of the Waipori Valley, the angular specimens of auriferous quartz, and the patches of highly auriferous angular drift found here and there in the ranges. At Bendigo, the Carrick Range, the Skipper’s Creek, the tracing of auriferous gullies and quartz specimens led, I was told, to the discovery of most of the principal reefs worked, though some showed by no means plain outcrops at the surface, partly by reason of their mullocky character, partly on account of being covered by detritus or being disturbed. And these features are the most serious obstacles page 172the intelligent prospector has to contend with in these districts for that the latter are promising fields for further discoveries of quartz reefs is plainly indicated by numerous auriferous alluvial gullies and creeks, and the occurrence of quartz specimens outside the drainage range of the known lines of reefs. The recent discovery by tracing specimens of a new reef in the Bendigo district presents a case in point. The same reasoning, based upon similar data, applies more or less to all the other reefing districts (Arrow Rough Ridge, etc.). And not to them alone, but also to the north and south slopes of the Obelisk Range, and to the rich alluvial diggings dotted along the edges of the Manuherikia, Idaburn, Upper Taieri, and other main valleys, though the reefs that in the latter cases supplied the gold to the drift would most likely lie in the ranges at the heads of, and bounding, the permanent creeks and rivers, entering the main valleys at, or in the neighbourhood of, the diggings. With regard to accepting the occurrence of massive auriferous drift or of mere surface at any place in rangy country as a promising indication of the existence of auriferous quartz reefs in the neighbourhood, the prospector ought to pay special attention, however, to one point, namely, to the nature of both the drift and the gold, i.e., whether the pebbles and gold-specks are waterworn or not. For, if the first is the case, the deposit may be a remnant of a former terrace formation, far transported from its original source; whilst the more angular the stones, the more hackly and crystalline the gold-specks are, the nearer lies their place of derivation. There is one district (I had no time to visit it) hitherto only known as an alluvial diggings, which, according to information kindly afforded me by Messrs. L. H. Preston, Jenkins, McDougall, and Smith, of Arrow, presents first-class indications of being a good reefing district. This refers to the 12-Mile Creek diggings, and mainly to the Great Barrier Range, in which the Arrow and 12-Mile Creek take their rise, and that forms the water-shed between them and the Shotover River, the position of the tract being pretty nearly in the line of strike of the Skipper’s Creek Reefs. A big reef runs right along the top of the range, and in the drift of the top part of the 12-Mile Creek, Scanlan’s Gully, Specimen Point, and in that of Rodger’s Gully and Tobin’s Point, at the head of the Arrow River, rich quartz specimens were frequently found, and shown at the stores and banks of Arrowtown, whilst at certain points in the 12-Mile Creek large quartz blocks can be seen—one of nearly ½ ton in weight—showing fine specks of gold all over. The gold obtained from Rodger’s Gully was generally so quartzose that it required careful crushing and separation of the quartz before it could be sold. Lower down country, about ½ mile from the junction of the 12-Mile Creek and Arrow River, a mullock reef, full of quartz veins, appearing as a wall-like formation on the mountain side, was cut through by a race, in which it proved to be 8 feet thick, show- page 173ing well defined walls, and dipping nearly vertical. Its promising appearance led a party of miners some time ago to prospect it, but, though the gold was found in the stuff, they deserted the reef again, and no work has been done on it since. Strong evidences of auriferous reefs are said to abound in many other places on the Arrow River and over the 12-Mile Hill, and only await the pick of the enterprising prospector for their development.

Concluding with a general comparison between this Province and Victoria as to the facilities and chances of prospecting, I must say that this work—looking at it in a strictly mining point of view only—is here much more difficult than in Victoria; for, whilst there, reefs consist mostly of massive white quartz, and are plainly exposed on the surface, they are here more frequently of a mullocky character, and more or less covered over by detrital matter. And there is besides one striking difference between the two countries, namely, that whilst in Victoria reefs abound all through the gold-fields, but, as the saying goes, ninety-nine in a hundred prove barren, here they are comparatively very scarce, but with this redeeming feature, that nearly everyone hitherto found has proved to be auriferous, and therefore, we may fairly assign the same chance to any ones discovered in future.