Gold in New Zealand.

Te Aroha News, Volume XXVI, Issue 43092, 14 May 1907, Page 2

Gold in New Zealand.

Mr W. Green, writing in the “ Mines Record ” on the undeveloped gold de. posits of New Zealand says : In the volcanic districts of the North the pyritic minerals, such as the sulphides and arsenides, occurring so plentifully in the rocks of the Thames and other miuing districts of the Hauraki Peninsula, are very poor in the precious metals in comparison with the gold-values of the same mineral belonging to the gold districts of the South. It is an undeniable fact that New Zealand possesses resources almost beyoud conception in her valuable deposits of pyritic minerals —as reefs, seams, and impregnations of country rock. There is a vast open field for the establishment of a permanent and very profitable industry in the treatment of pyritic minerals in New Zealand; and, seeing that Australia has long been awake to the value of this industry, why should not this colony 7 realise this asset also ?

Quartz reefs of the ordinary kindhaving never had an assay trial —are known to exist in great numbers all over New Zealand. There are also many reefs in gold-fields districts which have only been accorded a hurried test with a pestle and mortar that would perhaps show profitable value if treated in the laboratory. And many more outcrops of quartz have been passed over because no gold was visible. The history of each goldfield furnishes accounts of reefs worked for a period, and then abandoned at the water-level either because the capital ran out or because the free gold in the reef gave way to baser minerals and the yield of gold became unprofitable for the primitive miuing. In numerous instances reefs of this better kind have been mined afresh with profit under new appliances and im proved methods, and many of the others still left deserve another trial. The reefs of the Hauraki Peninsula are celebrated for their very rich concentrations of gold in strings and leaders occurring in decomposed zones and areas of volcanic rocks. The decomposed rooks called “ sandstone ” by the miners, are commonly found to be hornblende andesite, diabase, and feldspar porphyry. The reefs iu the andesite are the richest in gold, those with the diabase carry copper-pyrites and other minerals with the precious metals ; and the reefs, of the porphyry have a large proportion of silver in combination with the gold. These characteristics of the reefs are seen at Thames, Cor on andel, and other parts of the Peninsula. The zones of decomposition of the rocks, which seem to have had a mysterious origin, have, no doubt, been caused by the effect of thermal mineral waters welling up from fissures and spreading into the adjacent country 7 , and thus chemically changing all parts within their reach. Much of the quartz appears to be of secondary formation, and would likely have been deposited contemporary with the gold during the chemical process of alteration in the rock country. The small leaders of the quartz occurring in the decomposed “ sandstone are noted for their exceeding richness, specimen stone yieldiug upwards of .an ounce of gold per pound of quartz being of common occurrence in the Thames and Coromandel fields. _ . During the early period of gold-mining at the Thames some of the claims worked phenomenally rich patches of metal. The Moauataiari y ielded 14 600 oz. of gold from less than 21 tons of specimen stone in one fortnight, and. IO.OOOoz. of gold in one week. It seems impossible to estimate the full value of the metal obtained in these fields, but several million pounds’ worth are said to have been taken from, the small area around the Thames. The future of goldfields such as the Thames will depend largely on the eessful development of these mines at deeper levels. The problem of the continuation of the gold-prospects m depth, is iu some measure, solved by the theory of the chemical alteration of the rocks Hud deposition of the gold, as these conditions of auriferous area may be expected to be repeated from floor to floor in deoout, probably deeper than successful mining can be carried* on. also, other auriferous areas would likely occur under new conditions at intervals along the belt of country in strike. The famous Waihi mines have a great future in addition to tlieir successful past. These massive ore-b idles have been formed by solfatara agencies in the near vicinity of the geysers, which at no remote period were a feature in the land" scape between Te Aroha mountain aim Waihi. The nature of the origin of these reefs suggests also their continuance in depth, with other parrallel reefs yet to be found in lower levels by cross-driving. Other similar reef bo-lies should be sought for in situations near the sites of the old geysers round the Waihi Plain. Prospecting operations near Waikino have been in error through the drives having been put in above bed-rock, and Striking oulv the 'old lake strata of the plain. But this can be easily corrected.