“Two typical mines—­the Great Mercury Proprietary Gold Mine, of Kuaotunu, N.Z., the other, the Pambula, N.S.W.—­have lately been conducting a series of experiments with the object of saving their fine gold in an economical manner.  The last and best trials made by these companies were at the Ballarat School of Mines, where amalgamation without overflow was put to a crucial test, in each case with the gratifying result that ninety-six per cent of the precious metal was secured.  What this means to the Great Mercury Mine, for instance, can easily be imagined when it is understood that notwithstanding all the latest gold-saving adjuncts during the last six months 1260 tons of ore, worth 4l. 17s. 10 2_3d. a ton, have been put through for a saving of 1l. 9s. 1 2_3d. only; or in other words over two-thirds of the gold has gone to waste (for the time being) in the tailings, and in the tailings at the present moment lie the dividends that should have cheered shareholders’ hearts.

“And now for the modus operandi, which, it must be remembered, is not hedged in by big royalties to any one, rights, patent or otherwise.  The ore to be treated is first calcined, then put through a rock-breaker or stamper battery in a perfectly dry state.  If the battery is used, ordinary precautions, of course, must be taken to prevent waste, or the dust becoming obnoxious to the workmen.  The ore is then transferred to the Chilian mill and made to the consistency of porridge, the quicksilver being added.  When the principal work of amalgamation is done (experience soon teaching the amount of grinding necessary), from the Chilian mill the paste (so to say) is passed to a Wheeler or any other good pan of a similar type, when the gold-saving operation is completed.”

This being an experiment in the same direction as my own, I tried it on a small scale.  I calcined some very troublesome ore till it was fairly “sweet,” triturated it, and having reduced it with water to about the consistency of invalid’s gruel, put it into a little berdan pan made from a “camp oven,” which I had used for treating small quantities of concentrates, and from time to time drove a spray of mercury, wherein a small amount of zinc had been dissolved, into the pasty mass by means of a steam jet, added about half an ounce of sulphuric acid and kept the pan revolving for several hours.  The result was an unusually successful amalgamation and consequent extraction—­over ninety per cent.

Steam—­or to use the scientific term, hydro-thermal action—­has played such an important part in the deposition of metals that I cannot but think that under educated intelligence it will prove a powerful agent in their extraction.  About fourteen years ago I obtained some rather remarkable results from simply boiling auriferous ferro-sulphides in water.  There is in this alone an interesting, useful, and profitable field for investigation and experiment.