DEEP LEVEL MINING.

Otago Witness, Issue 2082, 18 January 1894, Page 13

DEEP LEVEL MINING.

Mr R. A. F. Murray, the Victorian Government geologist, who is to report upon deep level mining, wishes to return to Victoria early in February, and as there is no one to urge the claims of Otago ho is not likely to visit this district, but confine his attention to the West Coast aud the Thames. In the course of an interview with a Wellington Times representative, Mr Murray said that in Victoria they obtained as good stone out of the deep levels as from those nearer the surface, but having to take it in bulk from the deep levels, and not being able to pick and choose, the average results have not been so immensely rich as those obtained from the rich shoots which cropped out on the surface and were worked in the early days. But the returns from deep level mining have been more steady and permanent, especially at Bendigo and Ballarat. The prevailing feature of tho quartz reefs in the Bendigo district is that they occur in successive saddle formations. The reef will form an outcrop in the form of a saddle in one particular spot, aud thin out into " legs " on either side, while at varying depths beneat'a thi'i outcrop thure may be as many as 10 or 12 morf saddle formations.

<^ra^ BALIARAT UEEF3. In Ballarat two different classes of reefs are met with. One of these, which is found at Ballarat East, iB known as the " indicator." The rockbands there are nearly vertical in their course, aud what are known as the "indicators" are either certain thin bands of Blate charged with pyrites, or an occasional thin seam of the pyrites itself, sometimes no thicker than a crown piece, but traceable for long distances. These seams are crossed at intervals by flat veins of auriferous quartz-like floora, and they ore exceedingly rich at the points of intersection, where they sometimes yield nuggets of large size. Then, in addition, there are the ordinary lodes, more or less inclined from the vertical, sometimes nearly vertical, and making occasionally into large patches of quartz, and in other places pinching out into veins indicate! by mere fissures in the rocks. At;ain there are variations of these lodes, small in size, making bunches here and there and apparently dying out, but occasionally recovered further on either in length or depth. Then in the north-east part of what is called the Dark river, they have very well denned lodes, composed largely of pyrites intermixed with quartz. Those on the surface where the pyrites are decomposed have yielded fairly well to ordinary appliances, but when they get down to the undocomposed mineral special appliances are necessary for the saving and concentration of the pyrites and its treatment afterwards to extract the more precious metal.

TREATING QUARTZ. Referring to the systems in vogue for treating quartz, Mr Murray said that free milling quartz was simply crushed in batteries and passed through the boxes and over the tables. Of course in the case of pyrites, roasting is resorted to in order to enable the associated gold to be recovered. Sometimes the roasting is followed by amalgamation, and sometimes by chlorination, the necessary plant for this last-named process having been erected in two or three different places. In Victoria, as in New Zealand, some of gold is found in combination with Bilver, but this gold is of less than average value owing to this fact. Some of the Walhalla gold, for instance, is only worth £3 10s per oz owing to the admixture of silver with it.

AN INCREASING YIELD OF GOLD.

Mr Murray says that the increanid output of gold in Victoria la«t year as compared with the preceding year is principally owing to the greater attention that has been paid of late to scientific goldminine. both as regards alluvial and quartz mining. Then the burst-up of the land boom has had something to do with ie, because many people have been induced thereby to devote themselves to mining operations A large number of men have gone out prospecting duiiog the last year or two, and many of them have done well As a consequence, there has been a substantial revival at several of the old fields that were once goo'i. but had ben neglected for" a good many yeais past.

THE PROSPECTS OF DEEP LEVITL MINING,

Mr Murray Bees no reason why quartz should not be as rich at great depths as at the surface. Rich quartz, too, has been found in Victoria at all altitudes from 4000 ft to 5000 ft above the sea level, to more than 1000£t below it, and it has been found at all depths from the surface to as low as 2000 ft down. " The fact of the matter is," he added, "the gold occurs in shoots. One shoot dies out, and if you follow right down you drop upon another shoot."

ALLUVIAL MINING,

Referring to alluvial mining, Mr Murray said there was a good deal of it goiug on in the Ballarat district. In the Creswick country, which begins about 11 miles to the north of Ballarat, there are auriferous deposits extending for 20 miles beyond the present workings. lie understood that in "hydraulicking" New Zealand was able to teach lessons to Australia. "Of course," he remarked, " in New Zealand you have immen&e water power, and the stuff to operate on. In Victoria we have only a little of that hydraulic mining, in the mountainous parts, but nothing ou the scale that has been described to me as obtaining in New Zealand."