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The Pamphlet Collection of Sir Robert Stout: Volume 75

Does Gold Exist in Mine-Waters of Either or Both Circulations?

Does Gold Exist in Mine-Waters of Either or Both Circulations?

Prof. A. Liversidge* has pointed out that the search for gold in meteoric and mine-waters has not proved its presence in solution. It has been detected, but it may have been in mechanical suspension. So far as I know, Messrs. Norman Taylor and Cosmo Newbery, of the Victorian Geological Survey, are the only persons who have experimentally investigated this subject in these colonies. Mr. Newbery, who made the most experiments, said before the Victorian Royal Commission on Gold Mining that whenever he got gold, he got also angular fragments of quartz, which could find its way wherever gold could find its way, and both might have been conveyed mechanically.

The evidence for the existence of gold in mine-waters rests so far as I am aware, on the discovery of gold: (1) in boiler

* "On the Origin of Gold Nuggets." Roy. Soc. N. S. Wales, Apr. 6, 1893.

Report of the Commission, 1893, p. 68.

page 39 scale from boilers fed with mine-water; and (2) in wood taken from old mine-workings, where it had been covered for some time with mine-water—the latter being assumed to have carried dissolved gold into the timber, to be precipitated by the organic matter of the wood. But the finding of gold under such circumstances does not prove that it was in solution in mine-waters at deep levels. In the first case, the gold may have been carried into the boiler in suspension, along with the silt which all mine-waters contain. In the second case, even though gold may have been dissolved in the water surrounding the old timbers, it may have been brought into such solution by the action of air in the mine-workings, oxidizing sulphides of the rock to sulphates and setting free sulphuric acid, which, in turn, acting on the chlorides always present in mine-waters, would liberate hydrochloric acid. This acid, acting on oxides of manganese, would free chlorine, which would dissolve gold. This statement applies particularly to all mines the waters of which contain considerable iron. Every sample of chalybeate mine-water analyzed by me acted as a precipitant of gold when taken fresh from the workings, but as a solvent of gold at ordinary temperatures, in the presence of the oxides of manganese, when it had been exposed to the air for a week or two.

Mr. Newbery, however, distinctly said, in his testimony; already cited, that he found angular quartz which had been I soaked up into the timber examined, and that the gold might have been mechanically introduced in the same way.

With regard to the suspension of gold in mine-waters, the I following evidence, obtained by me last year, may be of interest.

In the Long Tunnel G. M. Co.'s mine at Walhalla, Gippsland, Victoria, one of the most productive mines in Australia,* the water pumped from various depths, down to about 2300 feet below the surface, is run into two large settling-tanks, before using. At the time of my visit one of these tanks contained a large quantity of fine silt, which had been suspended in the mine-water. I analyzed three samples of about 2 pounds each, first panning off the lighter part, and then assaying the residue. The first sample gave 0.0063 grain of gold; the second, no trace; and the third, 0.0175 grain.

* Mr. Ramsay Thompson, the general manager, to whom I am indebted for much kind assistance, informed me that up to December, 1894, this mine had produced over 22 tons of gold, and had paid £1,200,000 in dividends.

page 40

These results show that assays of boiler-scale do not necessarily prove that gold was dissolved in the water depositing it; and, also, that in all analyses even of samples from the vadose circulation, to test the presence of dissolved gold, care must be taken to free the water beforehand from every trace of suspended matter.

I have tested many old mine-timbers for gold. In every case the outside wood was chipped oft* to the depth of about ½-inch; and, when cracks appeared in the timber, about ½ inch on each side of the crack was also chipped off. These parts were burned, and analyzed separately from the inner portions.

The following table shows the results of several such analyses.