Littell's Living Age/Volume 129/Issue 1664/A Visit to a Japanese Silver-Mine

From Chambers' Journal.

A VISIT TO A JAPANESE SILVER-MINE.

A writer in the Hiogo News lately paid a visit to the great silver-mines of Ikuno, Japan, where European machinery has been introduced with great success; and as his account of what he saw is of considerable interest, we condense from it the following notes. On the hillside above the works, the objects which first attract the visitor's notice are the house (on a small platform) of the stationary engine, used to work the shaft now being driven down into the rock; a number of places like large rabbit-holes; and a tramway which runs round the face of the hill and connects these holes with a series of shoots down which the ore is passed to the works. These holes turn out to be galleries (six feet by six), which already measure eight miles in length; in them is seen the process of removing the ore by blasting, the fuses for which were at first imported from abroad, but are now made on the premises, at a saving of more than seventy-five per cent. The ore is broken up into pieces at the mouths of the shoots; the least rich lumps and those containing a large amount of other minerals are set apart for consumption at convenience; while the best pieces are sorted into five classes, their estimated values ranging from about sixteen to one thousand pounds per ton. These are pounded into dust in crushing-mills, and the dust baked in ovens with common salt (chloride of sodium). Hitherto the silver has been combined with sulphur, but in these ovens a chemical change takes place, the chlorine of the common salt combining with the silver and the ten or twelve per cent, of gold which the ore contains, and the sulphur of the silver combining with the sodium of the salt to make epsom salt, which goes into the river and poisons the fish. The ore — now a red earth — is then, by means of water and iron balls, thoroughly mixed with a large quantity of quicksilver by the aid of revolving drums. Under this process the quicksilver takes up the precious metal, and when the amalgamation is complete, the drums are emptied and the mud washed away. The combined metals are next treated by hydraulic pressure against a leather sieve, through which free mercury is extruded, leaving a putty-like brilliant white amalgam. Heated in iron retorts, the remaining mercury in the amalgam is driven off into a condenser to be used again; and the resulting lumps of metal having been fused with borax, which brings away some scoriæ and other impurities in the form of scum, are run into moulds and sent to the mint at Osaka. The metal contains, in the form in which it leaves Ikuno, about seventy per cent, of silver and ten of gold, the remaining twenty per cent, being nearly pure copper. The power utilized to drive the machinery at the Ikuno mines is mainly water, which is brought four miles and a half in an artificial canal, and may be taken for nine months in the year at two hundred and fifty gallons per second, with a fall of one hundred feet. During the rest of the year this water-supply fails, and the works are driven by steam. The Japanese government derives a handsome revenue from these mines, which will be greatly increased when the copper is worked independently.