ERROR OF QUARTZ MINING.

Thames Advertiser, Volume VIII, Issue 2149, 16 September 1875, Page 3

ERROR OF QUARTZ MINING.

Mr J. QoodaliL, 0.K., read a paper before tho Auckland Instituto on Monday evening on tho abovo subjeotj from which wo extract tho followiug Stamp-boxes aro generally constructed to hold iivo stamps; they aro of cast-iron in ono piece, aro thrco inches thick at bottom, and ono inch and a-lmlf to ono inch thich at tho sides, tho bottom aud sides aro protected from tho eroding action of tho stamps and quartz by castiron dies and linings. Tfo boxes havo two hoppers behind for feeding, and two openings in front for tho gratings to sorcon the crushed quartz. It has boen attomptod to havo grating openings behind tho box as well, but was found -not to answor, there being greater trouble to rogulato tho flow of water over tho two tables.

This remark applies .to side-openings also. Tho stump-boxes used at prosont are excellent. Tho only improvement I can suggest in thorn is, that tho openingß for the gratings wliieh aro now maao vertical should havo a forward inclination on tho top. This, I think, would allow tho crushed material to cscapo moro freely. Tho shoes of tho stamps and dies in tho boxes as well as tho linings aro at present mado of comparatively soft iroii. They should bo mado of tho hardest white iron and ohilled. If battery proprietors took Iho trouble of sending to England for their shoes, dies, and linings * they would find it to their advantago,~ not so much in cost as tho great saving in material and time lost in changing tho different parts when worn out. Tho cambs for raising tho stamps aro very seldom of a proper shape; they aro either too curved or 100 straight. They should bo so constructed that tho motion of tho stamp bo. uniform, and as soon as tho stamp is raised to its greatest hcight.it should drop, and not for ono moiuont beforo it is elevated for tho next stroko. Thoro is nodifficulty inconstructingacamb with the necessary curvo to do exactly as • required; and if so constructed a battory may bo driven up to 100 strokcß a minuto without tho 'risk of tho discs

striking tho cambs. Tho screens or grated for sifting tho crushed qunrlz usually used aro perforated iron«plates. Tho number of perforation? are from 100 to 132 holes to a square inch; tho grcator tho number tho finer tho holes. , It is

surprising how this kind has not ken superseded [by tho iron-wire grating, which is superior in many respects, especially in allowing moro materialpass through in a givon timo, thus causing a great saving in cost of crushing, and I am further convincod moro gold would also be saved, as, by tho present uso of quick* silver in tho boxes, tho amalgam formed is •unnecessarily battered, and converted into blo6k alia spongy amalgam—from being pulverised with bad minerals. This sickened amalgam will pass over silver-

tablefl, blankets, and oven tho settling pits, and no device <p savo it. Tho-silver-tables are sometimes mado iu ono plane, but generally in twoor Jlirco stops; tho inclination is usually 1 in MX Tho quicksilver-rifjples aro tbreo inches broad, three-eights deep, and ono half at bottom. 1 his enables the quicksilver and amalgam to bo scooped up readily when cleaning up. It is usual to'keep two ripples nearly as full of quicksilver as they will hold, and when the lower one is too full, a part of the quicksilver is lifted from it, and put back into tho. battery box. Tho blanket-streaks below tho

silvor-tables aro) about 20 fcot long. They aro so managed that a part oftliom may bo washed from time to time without stopping tho flow of water from tho rest, or allowing it to go on tho part from which the blanket had' been removed. Instead of blanket, baizo and ooarso plush havo been used with advantage. Shaking-tables were not tried excepting at ono battery; they proved very serviceable, but tho wear and tear was great, and as tho miners wcro not willing to pay an extra prico for its uso it was discontinued. Tho blanket-tailings, oc blanketings as thoy are otherwiso called, consist mostly of iron pyrites, and other sulphides combinod with quartz, and contain a fair proportion of gold, and some quicksilver and amalgam that had escaped |ovcr tho silver-tables. • Thcso tailings aro treated in berdans with- extra quicksilver, and ground up. Tho bordans now in uso at tho Thames, I think, exceed ia sizo'thoso in uso on any other gold field; thoy aro generally five feet in diameter, and I havo seen ono six feet. At ono time a couplo of rotating balls were considered suficient for tho amount of crushing icquirca; now tho general practice is to havo n loose ball as well as a stationary ono attached to a chain, and it is called a drag-ball. This drag does ■more work than a loose ball, but takes moro power than should Uo used in grinding, for tho drag grinds tho bowl as much as tho tailings. lam convinced that grinding and amalgamation can bo better accomplished <iu pans such as Wheeler's or Hepburn's than in berdans.. Pas treatment, however, lias tho sarno fault as bordan treatment; in both cases tho samo material is continually rcgrouud, thus a deal of labour is lost and quicksilver is used whilo grinding, This system accounts for tho great waeto of quicksilver at tho Thames, and if quicksilver is lost, gold is lost also. This battering nnd grinding of quicksilver and amalgam seems to mo to be the chief fault of crushing at tho Thames. It is tho basis of tho system there, and I fear will not bo stopped for somo time. How many thousands of pounds worth of gold has been carried away with sickened quicksilver, it will bo impossible to calculate, but I am convinced a great proportion of it could havo been saved.