FORTUNES IN TAILINGS

New Zealand Mail, Issue 1756, 1 November 1905, Page 65

FORTUNES IN TAILINGS

TWENTY-FIVE MILLION POUNDS. NEW PROCESS OF EXTRACTION. It is reported by cable that a Melbourne syndicate, backed by a capital of £350,000, is purchasing Broken Hill tailings and approximate tailings from other mines, and expects by a new method of extraction to obtain the vast sum of £25,000,000. A writer in the “Adelaide Register” says there has been considerable adverse criticism on the Barrier and in the cities concerning the extensive sales of tailings by the various Broken Hill companies, and arguments have been keen on the principle that a most valuable commodity is being sacrificed for only a few shillings per ton, but it must be taken into consideration that although the metal contents of these tailings are of fairly large gross value, due allowance must of necessity be made for certain contingencies which put another complexion on the matter. The position might be summed up under several headings:—(l) The first consideration would be by the purchasers the cost of*the plant necessary for the treatment of this hitherto waste product by whatever process may he adopted. (2) Then would. follow the actual cost of treatment of these tailings for the recovery of their zinc contents, which is probably from 7s to 9s per ton. (3) That although experiments in treatment processes have been proceeding for many years, and magnetic separation, saltcake, and acid. Cattermole and De Bavay processes have been evolved; still, so far as can be ascertained, none of these processes succeed in recovering more than 75 per cent, of the zinc, and from 60 to 70 per cent, of the lead and silver in these tailings, which heretofore have been a waste product. Moreover, the Sulnhide Corporation, for the year ending June, 1904, produced concentrate® which were below 3 y per cent, zinc, and it is said the grade of zinc concentrates produced by the Australian Metal Company, B.H. Proprietary, and block 14 rarely exceed 42 per cent. (41 The smeltino- of zinc concentrates and the Production therefrom of metallic zinc is admitted by all metallurgists to be not only a difficult but an expensive process, and the returning and smelting charges on this product are consequently high. Reliable figures on the last-named noint recently published in one of the Melbourne papers demonstrate the ro-

taming charges now ruling to be about <£Q per ton, but in computing the amount that shall be paid to the seller for the zinc concentrates, in the first nlace, practically 10 units of zinc are deducted, and the market price is paid for the balance. To instance, a 40 per cent, proportion is only paid on a 30 per cent, basis. The zinc concentrates do not contain high lead and silver values, but even these metals that are contained are largely discounted by the fact that in the case of lead no payment is made for the first 8 per cent., and only half market rates in excess of that. In silver a deduction of soz is an initiatory proceeding, and then only onehalf market rates for any excess is paid. The highest zinc concentrates that coujJ. be made from Broken Hill ores would be about 53 per cent., compared with 67 per cent., which is the theoretical value of zinc blende. Tliefintimate associates of Broken Hill blende are mainly manganic iron and copper, with only a trace of lead and silver, the difference being made up of sulphur. Taking all things into consideration, the actual buyer’s deduction for freight and smelting amounts to £lO or £ll per ton of concentrates sold. This will account for the milk in the cocoanut, otherwise the low price paid for tile concentrates. The price paid for block 10 tailings is said to be 6s 3d per ton, but the South’s figures are not yet available, and as the metal contents are lower the price paid will probably be correspondingly lower. (5) The current market price of zinc blende stands phenomenally high, namely, £27 ss, and never since 1895 for a whole or full year has zinc value been higher than £24 17s per ton, so that spelter is to-day standing at its almost record market price, and the question whether it will long continue at this high price is very problematical. However, apart from other considerations, to quote the gross value of the dumps on the price of zinc, which has for no one year been reached before, is not giving the matter fair justice. The converting into metallic zinc of these enormous dumps, representing close upon 6,000,000 tons, cannot he expected to have a hardening effect on the zinc market. This also is am important factor which has to be borne in mind by the management of the different mines .when disposing of their products.

It must be remembered that the distillation of zinc sulphides is a process of no recent date, and in Germany and America, where this process is in use for the production of spelter, some of the best trained metallurgists the world has ever seen have been experimenting for years, regardless of expense in efforts to discover more ready and cheaper means of spelter production from zinc sulphides. It is history to many Australians that a new process of zinc distillation known as Sulman Pickard process was adopted by the Sulphide Corporation at Cockle Creek, when it started production of spelter, but it is not generally known whether this new process is successful. Briefly outlined the sales and options of taillings so far comprise South, 702,000 tons; Block 10, 600,000 tons; and Block 14. 200,000 tons. In addition the South’s tailings output for nine years is disposed of. and an unknown output of the same material from Block 14 is also sold. Besides this the De Bavay process will be operating with the North’s 150,000 tons tailings, and the British tailings lump (about 200,000 tons) will be dealt with by some process at present not divulged. The Central Mine is dealing with its own material by the Mechernish and granulation processes, and the saltcake process is busy on the B.H. Proprietary. Summed up all the tailings dumps at Broken Hill, except only the Junction and Junction North, are arranged for.