Mercury hides in New Zealand Hills

Cue (NZERS), Issue 22, 30 April 1945, Page 21

Mercury hides in New Zealand Hills

nrllE mining of cinnabar, th c THE mining of cinnabar, th e * peculiar red ore from which mercury is derived, is probably the least known of New Zealand’ts industries, yet for over eighty years 'it has occupied a place in the Dominion’s mining history. Mercury production has never attained large-scale proportions in New Zealand. There have been years when it has had its (booms and there have been some periods when the output was very small, but it has never completely ceased. Just prior to the war, production fell low, but in 1942 there was a resurgence when new interests brought the latest machinery and modern methods to a desolate, abandoned field and a new hope to the hearts of old miners and prospectors who believe that great sources of cinnabar still lie unexplored.

Men who have 'Spent a life-time tunnelling into lonely hillsides in search of the precious ore are firm in their faith that there ns a great deal of mercury in some of Auckland’s hills. Cinnabar has been mined in the Kauaeranga valley just beyond Thames, at Puhipuhi, twenty-live miles from Whangarei, at Mackay town, alongside the Karangahake goldfield, and near the Ngawa springs not far 1 r om Kaikohe. It was only at Mackay town that the mine was closed through the exhaustion of the supply of ere. Even there, there are some who elieve that had better plant been used and other levels prospected the venture anght have been successful. There is a . <)ry . of adventure and toil, hope and Sfepair in the chequered history of

some of those northern cinnabar mines. When companies gave up, lone seekers remained, working with pick and pan and humble retorting furnace. Though their life was hard and their income small they were fascinated by the quest. It was the labour and zeal of isiich men that kept the industry alive.

The first locality which offered prospects of yielding cinnabar was at Ngawa, and it was there that the initial effort was made to place the production of mercury on a commercial basis. As early as 1860, people who gazed at the thermal springs had wondered at the globules of ’’isilvery white and metallic lustre” that they sometimes saw in the waters. Many and varied were the theories advanced, but the one most generally accepted was that a thermometer had been broken at some time when the temperature of the water was being taken. The real explanation is that cinnabar yields mercury by heating, and at Ngawa the element had been freed (by the hot mineral water of the springs.

In 1869, F. W. Hutton, F.G.S., visited the district on behalf of the Transactions of the New Zealand Institute. He found a large quantity of mercury both in cinnabar and in a pure state. An English industrial chemical firm spent large sums of money on cinnabar mining at Ngawa and worked over many acres. Having interests elsewhere in the world, where larger quantities of ore could be obtained at lesser cost, they eventually abandoned the New Zealand project. Some

machinery was removed, but three giant retorting tubes and certain other gear still remain in desolation. The Mackaytown mine was in the centre of the town. A strange re stone, that proved to be the valuable cinnabar, was found by a boy playing on a hillside. Over L 3,000 was spent on a plant erected at Mackaytown, but after five years it was dismantled and moved to the cinnabar field at Puhipuhi where deposits were large enough to make success a reasonable possibility. Men whose lives had been spent extracting wealth from the earth and stone believe that the lode at Mackaytown was only a fragment brought down by a landslide in years gone by, and that the main source is in the hills. The mercury industry at Puhipuhi was carried on until 1911. While difficulties were being experienced in recovering mercury the decision to cease production at Puhipuhi was due for the most part to a substantial fall in prices at that time. • On this field too, machinery was left to rust and furnaces to crumble. Individuals,

however, scratched on over the field long after the plant had ceased to operate. Pure mercury is a coherent mobile liquid which does not wet glass or other objects placed in it. With good reason 'is it also commonly called quicksilver. It is an elusive element indeed, though it is heavier than lead. Unlike any other metal it is liquid at ordinary temperature and does not alter by exposure to the air. Mercury is packed in cast iron flasks. There have been various types of oretreating plant used in mercury production in New Zealand. The main feature of the plant at Mackaytown was a big kiln into which a bag of charcoal and a bag of cinnabar were put alternately. The mercury was (sweated out and raked away with the ashes. At Ngawa there were steel retorting tubes about fifty feet long, and over six feet in diameter. The tubes, which were lined with fire-bricks, were revolved by giant gear wheels, the ore rolling over as it roasted. The site of a mercury production plant looks very much like that of a gold battery. The mouths of tunnels scar the hillsides; hoppers and chutes and ramshackle buildings make a drab and dismal scene. .. There was a close association between the mercury industry and gold mining in earlier days. In quartzmining the gold-bearing rock was crushed and the gold extracted by passing the crushed ore over mercury, which formed an amalgam with the gold. The whole output of some New Zealand cinnabar mines was utilised in this way. Since the introduction of another process on the goldfields the greater part of the mercury output has been used locally in other ways. Nearly ninety thousand pounds ot mercury has also been- exported. .* Under pressures of the war a new interest was taken in New Zealan s mercury industry and production was

in commenced at Puhipuhi. Cinnabar ore, inaccessible to the prospectors of years ago, is now being obtained by open-cast methods. Modern excavating "machinery has scooped away enormous quantities of earth to enable thc miners of today to reach the lode. Mercury is being recovered in a modern treatment plant with a capacity of fifty tens a day. This plant produced mercury to the value of over L 5,000 in the first year of operation. The Government, too, is taking a practical interest lin the industry, and have been prospecting a small occurrence of cinnabar at. Karangahake on the Ohinemuri River a few miles from Waihi. ' . '

Mercury has many uses. It is of great value in the manufacture of drugs and medicine, high explosives, and artists’ colours. Its use in thermometers and barometers is well known, but it also has a part in the manufacture of vapour boilers for power-steam production or heating purposes, arc rectifiers, power control switches and numerous scientific and electrical instruments. With the growth of industry which is likely in New Zealand after the war mercury

should find an ever-widening local market. ‘ ' Today, it does not seem to ; be/ unreasonable to hope that with modern machines to aid the search the great hidden wealth of the old prospectors dreams may yet be discovered in the northern hills. Mercury may not be such an elusive element after all.