The Miner.

Southern Cross, Volume 10, Issue 31, 8 November 1902, Page 3

The Miner.

NEW ZEALAND’S GOLD DEPOSITS. In closing a series of articles on this subject in the Mines Record, Mr A. McKay, Government Geologist, remarks : —The progress of mining in Otago during recent years has shown incontestably that for many years to come the chief and largest returns of gold must be derived from the extensive alluvial cement deposits ot various ages that are spread over the country from the neighbourhood of Oamaru, in the north-east, to Orepuki, in Southland, . and from the mouth of the Molyneux to Skipper’s Creek, and the Upper Shotover in the opposite direction. The richer and more accessible superficial deposits, no doubt, are rapidly being exhausted. Such deposits supplied almost all the gold during the first three years after the discovery at Gabriel’s Gully. In deep and wet ground the ordinary methods of mining failed to reach the gold, or reached it at such cost that its extraction was n« longer a profitable undertaking. Hence extensive and costly dams, head and tail races, diversion of streams, and the building of dredges to scoop up the golden sands of the river beds. Improvements in the construction of dredges, and the discovery that by means of these machines highly profitable returfts were to be obtained elsewhere than from the beds of the Molyneux and other large streams, so stimulated this form of the industry that for two or three years there was a veritable boom in dredging over the whole of Otago and the West Coast of the South Island. As a rule, dredging can be applied only to modern deposits or the superficial exposures of beds of greater age. Yet the field for dredging in Otago and Southland is very extensive, and owing to the difficulties hitherto in working wet ground much of what is now available for dredging is virgin ground. Dredging in the greater part deals only with the most modern gravels of the district, but there are places where older rocks are a'so being worked by means of dredges. Gravels of Pleistocene and Pliocene age are worked at many places by hydraulic sluicing at heights varying from aealevel 'up to 2,500 feet above the sea, and by the same process the older quartz drifts are worked at an elevation of 4000 feet above sea-level. The Maori bottom (Pliocene) and the younger and older quartz drifts are at places much disturbed, and the auriferous bands are sometimes in a vertical position. At Preservation Inlet and on the Wilson River Goldfields further discoveries of quartz lodes may be expected in the Silurian rocks of that district. At the same time alluvial mining should not be neglected, as there are possibilities in both directions of an improved condition of mining on this field.