C.—3

54

" The percentage of minerals in the tailings =18 per cent. The percentage of saving effected by concentration = 78-9 per cent. " The concentration of this ore, from the above results, may be considered satisfactory but a few remarks must be made as to the time when concentration must begin. The above 12* tons were collected m long buddies, where the refuse from 20 tons of quartz ought to have been all deposited. Total Value „ n m , in Quartz treated. er oent - Iwenty tons quartz, value £13 15s. per ton .-. = ... £275 0 0 = 100 Gold got from places and berdans = ... ... 115 90 = 41-9 Tailings ought .-. = ... £159 11 0= 50-1 Hence the total value of the 20 tons of tailings passing from the tables, blanketings, and berdans, = £159 lis., or £7 19s. 6d. per ton. "A certain quatity of these tailings, as skimmings and blanketings, were treated in berdans the refuse or waste from which assayed as follows :—

" The sample from which the above assays were made was almost pure iron—very, very fine— and it is worthy to note that the finest particles are the most valuable. t u " T1^ lff ?" c ? Cc in the value of the tailin gs which were collected in the pits, and that which they ought to be by calculation from the original value, and that value received as gold, is simply astonishing, and goes to prove that the very fine particles have been carried out of the pits by the large amount of water necessary to pass such heavily mineralised ore over plates; indeed, the percentage of saving is remarkably good considering the class of ore. * r-" I J, IS ' n ? I Y erth . eless . absurd to treat such ore by the ordinary battery process, without concentrating the tailings immediately ; they leave the plates or blanketings and by treating in such a manner 85 per cent, of the original value of the ore would be obtained. " To verify the above statement, look at the following figures :— " Twelve and a half tons settled from 20 tons, and assayed only £119s. per ton; whereas by calculation from the original value, these 12J tons ought to be £159 lis., -r- 12*. tons, = £12 15s. per ton "Hence we treated 62-5 per cent, of the bulk, containing 152 per cent, of the value, thus proving conclusively concentration must be introduced immediately the tailings pass from the "An analysis of the concentrates proved them to be pure iron, with a small percentage of silica " lhis report is born out by Mr. Park, of the School of Mines, who made assays from samples taken at intervals during the crushing of the 20 tons of quartz referred to, which Mr. Park states the assay-value to be £274 10s. The total return from all sources, after going through the ordinary battery process of treatment, was 430z. 16dwt. of melted bullion, valued at £110 155., which represented a saving of only 40-3 per cent, of the assay-value. Hape Creek. There has been a slight increase in the yield of gold from this part of the field last year, the operations being principally carried on by twenty-two tributers, only three men being employed on wages. Ihe total quantity of quartz crushed, 868*, tons, which yielded 5750z. lOdwt. of gold. Tailings Plant. The principal tailings plants on the Thames are those belonging to Mr. Brown of Tararu and those belonging to the Foreshore Tailings Company. The plant at Tararu consists of McKay 'pans which without exception, are the best grinding pans yet introduced into the colony, and if properly worked, and the mullers slightly lifted when the quicksilver is added, these pans when working in charges will do as efficient work as any yet on the field; but while admitting this, there is a considerable loss m bullion with all pans which cannot be avoided. The Foreshore Tailings Company have a plant of twelve Watson-Denny pans, which have a continuous discharge. This principle of grinding-pan is held to be more convenient to use, as the tailings irom the tables can be run directly into them ; but neither these nor any of the continuous discharge grindmg-pans save a large percentage of the bullion. Indeed, until recently on this field ™l ? e Au mmc " managers would not credit that the y were losin S so much gold, they beino- always satisfied they were at least getting 75 per cent, of the assay-value of the bullion. But the recent assays made for several companies by Mr. Park shows the necessity of a systematic sampling

Bullion. Gold per ton. Silver per ton. Value per ton. Total Values. Tailings, 12J tons ... Oz. dwt. gr. 2 18 19 Oz. dwt. gr. 0 8 4 Oz. dwt. gr. 2 10 15 £ a. d. 1 19 0 £ 24 s. 7 d. 6 Concentrates, 2-J- tons Eefuse, 10 tons 10 0 5 19 4 21 1 17 12 0 1 15 8 0 8 3 7 6 8 11 0 0 6 10 19 4 9 3 8 4 Loss ... £1 14 5

Bullion per ton. Gold per ton. Silver. Value per ton. I. II. Oz. dwt. gr. 4 1 16 4 0 0 Oz. dwt. gr. 2 1 12 1 19 4 Oz. dwt. gr. 2 0 4 2 0 20 £ s. 8 11 8 1 d. 0 8