Art. LVII.—On the Occurrence of Large Bodies of Ferrous Sulphate in the Gold-mines of Thames Goldfield.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 37, 1904, Page 551

Art. LVII.—On the Occurrence of Large Bodies of Ferrous Sulphate in the Gold-mines of Thames Goldfield. By Matthew Paul, Mine-manager. Communicated by Professor James Park. [Read before the Otago Institute, 8th November, 1904.] Sulphate of iron is found in large deposits in the old workings on the Thames Goldfields, principally in the Kuranui, Caledonian, Waiotahi, Victoria, and Moanataiari Mines, situated west or seaward of the Great Moanataiari Fault. In No. 3 level in the Kuranui-Caledonian Mine, in an old cross-cut drive (347 ft. from surface) which was driven for the purpose of connecting with the Waiotahi Mine some twenty-five years ago, there is a very large deposit of this mineral. In some parts it has almost filled this drive up, and one would think at first sight that the country-rock had fallen away, but on closer examination the whole of this is found to be sulphate of iron. In this level there is scarcely any moisture to be seen, and the deposit grows on the top,

bottom, and sides of the drive. It is very pale-green in colour, and when exposed to the atmosphere for some time gradually melts away, but if put under a glass case it keeps its form and colour for many years. At this particular level the mineral is very pleasing to the eye by candle-light, as nearly all the colours of the rainbow are reflected from its surface. Ferrous sulphate also occurs at No. 1 level (210 ft.)—in one case the characteristics being somewhat similar to that already described, but in another place the reason for its formation can be plainly seen. The water dropping from the roof has formed stalactites of all shapes and size, some of them very beautiful in form and colour, many reaching from the top to the bottom of these old drives. The mineral is very brittle; and associated with it there is epsomite in large quantities, depending from the roof and sides of the drive in dense snow-white bundles like masses of fine-spun silk. The mineral filaments possess a silky lustre, and vary from 4 in. to 8 in. long In other parts of the mines there is a dark-green sulphate of iron, which is only found in drives where the reefs or veins have contained large quantities of iron-pyrites. The water dropping from the roof forms stalactites varying in size but not in colour. This variety is much harder than the former, and as brittle as glass. There can be no doubt but that this formation is caused by the decomposition of iron-pyrites; and, although sulphate of iron is extensively used in the manufacture of manures, some of this sent for analysis was found to contain so much acid as to be of no commercial value. Its composition is as follows: FeSO4 + 7 H2O, equal to sulphur-trioxide 28.8, iron-protoxide 25.9, water 45.3, in 100 parts.