LOSS OF GOLD IN MILL TAILINGS.

Mount Ida Chronicle, Volume V, Issue 275, 12 June 1874, Page 2

LOSS OF GOLD IN MILL TAILINGS.

■ 1.. Concluding- our l extracts from ' Mr. Skey's valuable paper, we shall briefly i endeavor-to give a clear indication of the direction':! which' the' experiments made point to as the- true- remedial one for the loss of gold sustained. The' analyist is of opinion that—T-he— Chilian Will, seems itpo j slojy besides, ?i:inuch complaint is made that the'lossi of mercury is very great by this mill. With the burdan, ■.thpugh, certainly,-an.: excellent apparatus for rich hand._samples or blanketings, evidently, t on' the ?part:of the few managers, who use them, such a disposi- ■ tipn.tp run themjeither ;too\ fast,; or iwith so muchb water —m fact to give them too I much "work—-that one docs not like to re-commerfd-/them' at'all.' They are rather ;idf|fieieht,;in grinding power, lor. profitable P? e Qs.9[ scale, as at. present construe* ;t e „d,,But f if some-means could be devised for .increasing. this considerably,, say by fixed shoes, instead of balls, or a mixture of the ,trcp,, they, might be,found to work well. Concentration .of the. heavier portions of the. auriferous, rocks, and the treatment ofthe residues' Tjy special processes, certainly m erits .great .attenti on.— —JReverting again to the flowing of the mercury, Mr. Skey re-statesr-rThe -principal cause being •the pressure of sulphate of iron in the reef stuff, and the fact being that this salt ' is freely J soluble in'-'water, it naturally oe- | curs that one way of 'preventing tlie mercury beipg Effected', is, to wash the/aurf'ferous stuff impregnated with this salt before stamping. Whether this is practicable is at once- suggested. Mr. Skey cannot tell: he thinks, however, it could. be applied where tlie reef is porous or in-'cpHerent-j-,J[e. state's, in conclusion, tliat —Tp a certain extent, where gppd water is used for the staArpers and tables, the ill effects of the. metallic sulphates present -in-the reefs are diminished.—There is. a danger, however, that the water used may itself.-contain the obnoxious' sulphate. We learn that—The use of water for these purposes, containing /any nptable quantity pf sulphates, acts even more prejudicially than the sulphates naturally existing in the stuff itself, even were they ever so abundant: flowing, in such a case, becomes a chronic camplaint. Merely'as a .?,be ; naical feat, it is very easy to overcpme the actipn pf the sulphates; but, for stampers potables, where such immense quantities , of water .are used," it would scarcely pay to manipulate the water itself. , .this reason Mr. Skey is. of case, of the battary tables, it-is ,PPlj the ' mercury we. can profitably influence by. the additien to it of sodium, P r :.th. e sodium, amalgam, as suggested:by Mr., Ci'ookes.. . . . . ; . In working up the blanketings either the water or mercury.should certainly be treated: che- ■ P^iQ^Uy;» i the,. blanketi stones being -generally v very-: pyritous, and the amalgam present in a flowing condition. Cyanide which /appears .to- be the agepk yet-administered to the' water 4 or,.keeping- the?mercury-bright, acts ad r miiably. - It is- a_ solvent' for the ; ihietals gpld, silver, and. mercury singly, but I have ( found experimentally that in the ,presenceof the three together it only dissolves the silver''and the mercury—-at least to an appreciable" extent, and there is therefore' not that loss "of gold incurred rrpm its use which some persons have anticipated. Its expense, however, requires that it only be applied to that work which a, cheaper palfc cannot, effect. Thus .the neutralizing of the acid substances in the blanketings may be safely and. cheaply performed by worki'ng soda, W after thi liquid and solid matters are feebly alkaline,; then[ the cyanide, .caii -be added ftjll any _ mercurial v; globules in sight in tHe jell-stirred liquid, are bright and sharply denned. With reference to the remedies •^B;M ..PRPloyed against. : the newlv-dis-coyered absortive property of- gold forsulphuretted hydrogen, I woulf remark that the = -frequency ■ with's which *nktaral' surfaces of native gold- must be tarnished by this substance renders it a matter of importance to ascertain' the state of these surfaces, and, in case of their being sulphurised,., to take every practical means toy effecting the exposure of the pure metal to.. various amalgama prs. We may have the mereury ever so clean, ever bo.'positive, as it were,' to the gold ; we may even put it in an electiical state* as'was proposed to me by an enterprising gold-mining manager, but. if he-gold is coated ; with a continuous film ot any negative substance, however thin, it-is certain tliere would be np cpntactbetween the two metals, and consequently amalgamation could not proceed/ ' Indeed,/we have a far better chance of obtpmng; amalgamation when of the two metals the mercury .is tlie tarnished one, since even then it yields a tolerably'clean surface to the slightest, pressure or .friction. _Ther'e is np doubt'that the operation of extracting.the stone from the reef, and the present method of working it at the mills, tend greatly, by mere abrasion, to remove old surfaces, and thus expose clean metal. These should be pW"-oi-fui ;neasa:es in thougn their Uuuiy "iij~.thiß .respect has

not before been suspected. Ido not know that we can pusli this mechanical abrasion much farther than is at present done, for it seems there is a point, or ra- . ther a degreS of fineness passed which the proportion of mercury and amalgam which escapes is so large as to neutralize the good effects. Mr. Skey finally summarises hiß experiments : 1. Pure golil-kept in strong solution of protosulphate of iron for one, week, in an open vessel, and then worked, amalgamated very well at the end of tho term, r 2.. Snlphurised gold, treated in man- ■■■■'. ner' detailed above, would not amalgamate at all. 3. Pure gold freely exposed to the V v \ *j >\ air three at a v distancie from laboratory, readily amalgamates: 4. Sulphurised gold exposed, as in No. 3, for six days, would not amalgamate.. ... •, s.Pure, golli placed .in solution of , photosulphate of .irons aloilg with; ~ sulphide of-antimony, was>renderedunamalgamable in twenty- . , . four hours. ...... ; 6. The same' .effects When* ' . *ifon pyrites" (slightly cuprebusj was substituted for the antimony sulphide. \- - The experiments detailed are obviously too limited in. scope'and number to allow of ■ t any ■, very, specific ( .\deduc,tion /.being . u.ppn Jhem s,vbufc: their.'general 4 tendency is greatly iri vmy .. con viction,. • that m.piosfc • cases • n , ~, must.be greatly Rulplwrised;'-o\-, : • v .Finally, Mr. Skey'concludos that her iVincliherd 'to think the greater portion of the loss; puting aside mechanical, .improvements—is. made up of gold which , become sult phurisea upon: ifis 'surfaces, and remained ' '