37

a—3

This shows a falling-off in the yield of gold in three localities of about 7,0920z.; but in the other localities the yield has increased, and even in the localities where the largest falling-off has occurred—namely, Grahamstown and Waiotahi—the average yield per man last year was 44foz. and 460z. respectively, which cannot be considered a low average. It certainly shows that the ground is still capable of producing sufficient gold to give those employed fair wages. The fact of the Saxon Company suspending their operations at the low levels, where an average of ninety-two men found constant employment, the company also being a large contributor towards the payment of drainage-expenses, has cast for a time a gloom over the place. But, to take the district as a whole, mining cannot be said to be in a bad state. The principal gold-producing companies last year were as follow: — Sylvia Company. —This company has gone to a large expenditure in the erection of concentrating machinery and appliances for extracting the gold and silver from the ore. They have one of the most complete plants in the Colony for the class of ore there is to deal with in the Upper Tararu district. The ore contains galena, copper-pyrites, blende, gold, and silver, and is therefore of a refractory character, requiring a different process of treatment from the general bulk of the ore in the Thames District. During last year 3,480 tons of ore was crushed, which yielded 1,1530z. gold, and about 335 tons of concentrates, which yielded 9,8640z. of bullion, representing a value of £7,874, the value of the gold being about £4,202, making the total receipts for the year £12,076. The workings in the mine have been confined to stoping from the No. 2 and No. 3 levels, and a commencement has been made to construct another level from the side of the terrace adjoining Tararu Creek, which, when completed, will give 200 ft. of backs to the No. 3 level. The character of the ore and size of the lodes continue about the same as for the previous year. The managing director, Dr. Scheidel, speaks very hopefully of the lode continuing to a great depth. Taking the quantity of ore treated last year—namely, 3,480 tons—and the value of the gold and bullion obtained—£l2,o76 —gives an average value of about £3 9s. sd. per ton. The following description of the mode of treating the ore at the Sylvia Company's works where the Cassell process is used, was handed to me by Dr. Scheidel, Ph.D., Assoc. University of Freiberg, Germany, who is managing director for the company:— " Treatment of Sylvia Ores. "I have the honour, at your request, to place at your disposal a brief account of the results obtained during the first year of operations in the concentrating works of the Sylvia Company, Tararu, Thames, and on the cyanide extraction plant, lately added to the company's gold-saving appliances. "I gave you last year a description of the company's ore-dressing plant, constructed and erected by Mr. H. W. F. Kayser and myself, and I am now able to report that the first year's operations realised fully the expectations as to the efficiency of the plant. " The total quantity of quartz put through the mill of ten heads on 332 days amounted to 5,300 tons, or about 16 tons every twenty-four hours. The battery is quite capable of putting through 25 tons per day, but the scarcity of water during a lengthened period reduced the motive-power, and thereby the capacity of the crushing plant, to such an extent as to lower the day's average to above figure. The total amount of concentrates obtained from the crushing-dirt amounted to 440 tons, of £12,033 value. The value of the crushing-dirt varied considerably—the great bulk of the quartz assayed before treatment between £3 and £4, a considerable tonnage reached as high as £10 per ton, and at other times very low-grade stuff had to be dealt with. The value of the tailings going to waste varied between 9s. and 15s. per ton : occasionally higher figures were obtained, the consequence of a failing water-supply : the concentrating machinery requires a certain speed, corresponding with eighty-five strokes of the stamps per minute, and gives at such pace better results in dressing than at a reduced rate of motion. The amount of free gold saved on the plates amounted to 1,2780z., value £4,629, or £3 12s. per ounce. The quantity of free gold saved per ton of ore amounted to 4dwt. 19gr., value 17s. sd. The amount of concentrates saved averaged 8-3 per cent., one ton of quartz yielding lewt. Iqr. 171b., of the value of £2 ss. sd. The total value saved per ton of crushingdirt amounted, between concentrates and free gold, to £2 9s. Bd., the average value saved of the assayvalue per ton of ore being estimated at 80 per cent. The concentrates obtained were classed as follows : Jigger concentrates, first-class slime concentrates, second-class slime concentrates, and buddle concentrates. The average amount of jigger concentrates amounted to 4oz. sdwt. of gold and 20oz. of silver —value £20 —per ton. Such concentrates contain a small percentage of galena ; they consist chiefly of iron- and copper-pyrites and zinc-blende; they further contain a small percentage of quartz, which it has not been found advantageous to separate completely. The first-class slime concentrates represent only 32-5 per cent, of the total production of concentrates, but their value is equal to 52 per cent, of total value. They contain a high percentage of sulphide of lead —in some instances as high as 20 per cent.; they are almost absolutely clean, containing only a fraction of 1 per cent, of quartz. Although .solid veins of rich galena are only seldom met with, sulphide of lead is pretty equally distributed all over the mine in small quantities. It slimes considerably in the crushing process, and carries a higher percentage of gold and silver than any of the other minerals composing the concentrates. Its presence is always conspicuous, and quite a feature on the slime-concen-trating tables. From clean galena on the tables as high assays as 48oz. of gold and 98oz. of silver, value £206 per ton, have been occasionally obtained. The average assay-value of first-class slimes amounted to lOoz. 6dwt. of gold, and 440z. of silver per ton, value £47 16s. The single assays varied considerably : values as high as £95 per ton have been obtained. " Differing from methods applied to other ores, I finish the first-class slimes in one sole operation, which way of proceeding I found most expedient and economical. The middle products from the slime-tables go to a triple table, where they are finished. In the finished state they are called secondclass slime concentrates. Their total production amounted to 93 tons, their value to £1,730. They contained in average—gold, 4oz. sdwt.; silver, 20oz. They contain a very small percentage of