AMALGAMATION OF GOLD.

Tuapeka Times, Volume III, Issue 208, 25 January 1872, Page 7

AMALGAMATION OF GOLD.

Mr. W. Skey, Government Analyst, recently instituted a scries of experiments for the purpose of ascertaining the actual quantity of gold which escapes in course of extraction from the various mills at the Thames. The following are extracts from his report : —

) SUMJfATIY OP BESUXTS. | From a perusal of these tables, the following general results appear : — I 1. The amount of gold allow separable by an almost exhaustive amalgamative process from numerous samples of tailings taken quite indiscriminately |rom this (Thames) field has varied from a minimum of 1 dwt. 14< grs., to a maximum of 1 oz. 19 dwt. 18 grs., as calculated upon a ton of the sample, hrhile the assay yield has been from 2 dwt. to 1 oz. 9 dwt. 2 grs. of pure gold j>er ton for the same samples respectively. 2. The yield thus obtained does not bear any fixed or definite ratio to that jbtained in the first instance from the same stuff at the batteries. I 3. In respect to quality, the gold given up to this re-amalgamation is gene ftilly poorer than that which has been taken at the mills by the first amalgamation. n J 4 Roasting the stuff previous to amalgamation does not, as a rule, raise the ]6eld of gold alloy ; but the gold so obtained is uniformly finer. In making proper deductions from the results above summarised in referjnee to the actual loss of gold entailed by the present way of milling, it is ifccessary to make allowance for the concentration of the stuff in passing tlrough these mills. p (The amount of this is not a fixed quantity, but varies with the kind of stuff, tlte degree of fineness to which it is crushed, the volume and fall of water used, and mode of settling. It would be difficult, therefore, to. do more than make a vague allowance for thb loss : and this is stated by several of the managers of the batteries at from 3at0.50 per cent, upou the stuff before crushing. \ had not time to fully investigate into this matter, but from the fow experintnts I was able to make in this direction, I believe these figures to be apprckimately correct. %ese experiments were confined to the testing of the actual loss in earthy aiafcer incurred by my particular mode of sampling, as stated on page 71, the greatest loss being for the Una battery, and amounting to 45 3 per cent, while thelowest was 20 per cent. Cfi the whole, therefore, and considering that the larger proportion of gold lostwill remain with the coarser portions of the earthy matter saved, it will be projbr to reduce the figures in the 2nd column to about two-thirds of their ■valuL in order to get au approximation to the actual loss of gold upon the actiil quantity of stuff crushed. " Sfoject to the reductions consequent upon making these allowances, the loss of gdd for many of these batteries amounts to 30 or 40 per cent, upon that capable of being extracted by careful and prolonged amalgamation; or to 35 and 5 per cent, on the quantity actually present in the stone, as shown by assail Cdh pared to the loss experienced on other goldfields, where amalgamation is thdprocess used, this does not appear excessively high. Still, it is very unsatefactory as regards our present gold-saving arrangements, to know that we ai frequently throwing away nearly as much of the precious metal as is savedland with a view to the reduction of these losses, the main causes of this loss vjll now be, considered. I (To be continued.)

Rate of yield per ton. Name of Claim. By Mortar. After I Roasting. Actual yield of original stuff at Mills. By burdan. 'Assay yield Onehunga Shamrock Una Berkeley Castle ... Bull's Scottish Chief Golden Crown Young American ... Kuranui oz. dwt. gr. 1 0 2 3 2 6 2 10 2 11 2 11 2 14. 2 22" 3 1 3 16 3 20 4 0 4 7 4 14 4 14 5 1 5 2 5 9 5 17 5 19 5 20 6 10 7 14 7 21 7 22 8 6 12 22 13 2 1 13 0 1 5 21 1 39 18 clwt. gr. 1 14 dwt. gr. .oz. dwt. gr. loz., nearly Unascertained, small I to l£ oz. 14 oz. 1$ cz. 1 oz. 12 dwts. to 1 oz. 1A oz. 1 £ oz. l| oz. 2oz. I ... I*2o fl7 I 1 2* 18 • ... 2 17 2 20 4 7 211 Flying Cloud Just-in-time Mariner's Reef ... Moanataiari Waitemata Ladybird & Hand of Hunt's [Friendship Long Drive Inverness Golden Crown Little Nell Hunt's Una 4 0 5 17 6*17 7 7 8* 12 8 "l 4 8* 23 ... 2oz. £oz. 1 oz. 6 dwts. A little over 2 oz. 2oz. 4 to 5 oz. I ozr j oz. 2oz. 6 2 10 20 7 4 5 23 10 22 J 12 3 ... • Wandering Star . . . Una 8* 1 1 oz: l£oz. 1 to 2 oz. 2oz. 2oz. 5 oz. 4 to 5 oz. 14*" 8 • ... City of Dunedin ... , Belfast 15 19 14 8 17 5 Golden Crown 1 9 2 ...