ON THE LOSS AND SAVING OF FINE GOLD.

Otago Witness, Issue 1891, 1 May 1890, Page 11

ON THE LOSS AND SAVING OF FINE GOLD.

(By J. A. Milleh.) I.

A greah deal of sensational nonsense is talked and written from time to time on this subject, without any reference to the fundamental distinctions into which tbo question naturally dividss itself. The subject, of great importance at a\) times, is of commanding interest at the present moment, when a number of mining ventures are being fitarted whose very life dr-pends upon the efficiency of the gold saving apparatus euployed to arrest the greatest quantity of fine gold, which, at the samo timo, shall be capable of treating large quantities of gravel, and which must be independent of the nice adjustment-,-; of the regular proportions in which the stuff and water are paid intp the apparatus. These latter details create the real difficulties which it is the object of tho gold saver to combat and overcome.

As stated, tho q'l^tion resolves itself inro two fundamental divisions, each of which is essentially distinct from the other. The one at the present moment of the most pressing urgency ar d actual importance refers to tho saving of fine gold from alluvial deposits whero the material requires to be treated in tun largest possible quantities in the shortest possible time, without paying too much at tontion to tho proportions in wbieh cither "<tnflt or water are fed to the apparatus ; and the other has ref' renc; to crushed material a r d quartz tailinpr^, o/T>rin? far less difficulty, ar d compard with the former Is perhaps of secoidp.ry importance.

THE SAVING OF GOLD FROM ALLUVIAL DEPOSI! S,

as the more important, may tbereforo be t-nken first. Analytically considered, nil thf appliinc s devised for the saving of gold from auriferous drifts resolvo thr-mselves into on" and thf s -m<i principle — namely, the ripple ; whether applied as the longitudinal ripple, Venetian blin-i* — right and r versed, the curved ripple (Mr Aapinall's patent), the diasono! and douMa diagonal ripp'e, paving stone", fern tree block, grass, scrub, ferns, blankets, (runny bags, cocoal.ufc matting, pluah, hides (\mooth haired and woolley ones)— in facb. any devicw of this kind has the principle of tho ripple underlying it, and all and each of these varieties of its application are subject to tho same objection, and t*ia!; is that they all choke as soon as th=y fill, set hard, and lose thoir effectiveness after a very shcrb time of actual u'i!>. All the above varir.tifp of ripples are applied in ground '.lui^ew or bluice boxes diioharging tbo sUiff iv :ha rlirec tion of tho flow of the water ; thm all tho gol I that t;;vuuot find a lodgment ia nac of to j r'pi>U/i i= hnp-ka'-.ly c:irri«.l feway, an.!, a- C^c ai tliH proeeudof (tcattuenii is concerned, i-j h<n\,. Bo far as experiments have gone, no means

have been devised to save gold by changing the direction or breaking the current in aay other way than by the ripples. Drops of varying heights, ifc is true, have been employed withmuch success ; but where this has been most pronounced has been in cases where clayey and otherwise tenacious gravel deposits were treated, which were broken up and thoroughly disintegrated by the falling water, and the gold separated aud saved which would otherwise have betn carried away, not by the water directly, but in the lumps originally containing it. However,

THE DBOP as a means in the break of a current, in the very limited choice there is in the variety of gold saving devices, is deserving of more attention than it has received, and there is no reason why it should not be employed in all cases where ifc can be conveniently introduced. The best known way to utilise the drop is to let the stuff and water fall upon a woolly skin stretched over a frame. The weight of tho water and stuff depresses the skin, saucer fashion, the vibrations of the skin discharging the gravel and preventing; the wool being choked with sand, I believe Messrs Davis Bros., at Stony Creek Terrace, Shotover, are using bearskins imported from California for the purpose in this manner, and they were amongst the first to utilise the drop in the manner described. They are generally credited with saving the finest gold that is sold in Otago.

QUICKSILVER, also, has been used in sluices for the purpose of gold saving, but for years past has been losing favour with practical men. The objection to quicksilver is that, independent of its liability to become coated with foreign matter and becoming comparatively inactive at a low temperature, there is the difficulty in bringing the fine and light gold in contact with it; and it has been observed that the gold saved in sluices by quicksilver is anything but the finest and lightest as compared with that saved in the ripples of the same sluices — or, in other words, the gold retained by the quicksilver would have been saved, every speck of it, without the aid of mercury. Another objection is that, no matter h w caroful anyone may be in the use of quicksilver, or whatever provision may be made for its protection in the sluice, there is always a considerable loss of the silver itself, amounting to a current expense of some importance.

It can, of course, serve no purpose to refer to the different attempts made from time to time ab introducing now gold - saving machines adapted to sluicing on a large scale which never attained to any practical value, although it ia probable that amongst them the keynote to the solution of the difficult question may already have bepn given that will ultimately solve the problem.

It has been a matter of common remark, and no small surprise, that, no gold 6aving appliances were shown at the mineral courts of the late New Zealand Exhibition, with (ho exception of Mr "VVehb'« machine, which, however, would hardly ausntr for the treatment of very large quantities ; and another exhibited in, if I mistake not, the V nccnt County bay, which has somo features to recommend it to those interested in tin question, alfcbough if; would hanily answer for dredges as at; present constructed. Even Now South Waks had nothing to s-how in tho w,.y of gold paving or gold washing nj.pliauces This ia all tho moro surprising becaubo all such apparatus appliod to the treatment of largo quantities of stuff must of necessity be pimple, and therefore easily modelled, while it is of the utmost importance to the whole of the gold mining industry.

Ife would appear ''hat the question has puzzled even the cute Yankee miners, who iv many j rpppf-cKs take the lead in inventions aid improvements. Indeed, it may be said that there has beeu no invention in this department of mining prnctioe since the first introduction or adoption of the ripple, and even old Nature herself renders no new aid in unravelling the difficulty. OLD NATURE'S PLAN. Hivers, which are otbi'n referred to !>s sluice or tail races, though they illu?trato tho deposition of gold by a current in a goner.il way, offer only several varieties in tho application of tho ripple, which bave received absolutely no ntfc,;ntiou from practical men ; yet by thbir aid nml tbo manner of their employment, Nature br.s succeeded in saving the finest of the line gold iv her river br>ds mjcl water channels of past ayes, as well as in thoso of tho present time Now, when ifc hus become the task of the miner lo extract from Nature.'? treasure trove tho stores of fine gold deposited therein, the closest shirty of the plan adopted by Nature recommends itself as affording tho nearest clue to the sr cret of br-r success. Nor is this a very difficult nmttnr. Having first minutely studied and observed tbo action of running water in natural channel", it only remains to copy the same cauips and tho same results will follow, or else analogy and logic are alike false and deceptive.

It goes without saying that ifc cannot be hoped to imitate Nature in the magnitude of bcr sluicing operations on the ono haml, nor on tho othor is it necessary or desirable to spend over the operation the same amount of timo as required for propounding tho puzzle miners now strive to solve. A company which promise 8 to pay dividends in in uncertain number of millions of years wouM scarcely float at the present tirnf, however glowing experts' reports may bo mirlo to be — as it is, they (tbo dividends, not tho expirts' reports) are quite uncertain enough. It behoves us therefore to be satisfied with a compromise, and in a modest way, by sruill means try to accomplish our task, remembering that Nature has objects of her own, which to atfiain. sho takes hor own time ; yefc she never Fnik in attaining what pbo undprfcak^s, without havinjj rrfunrp to lame explanations or compi'o'.uisuij-; excuses. Moral : Man, especially whon ho is a mining investor, has much to learn from Nature.