Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/443

1869.] ULRICH—"NUGGETTY REEF." 333 granite, dipping east at an angle of 18°, was again struck and sunk into for 20 feet. But as it showed no change of any kind (being solid, and nearly without joint or crack), further sinking was considered useless, under the, no doubt well-founded, supposition that this last granite represented the real massive formation of the rock, dipping this way from the neighbouring surface-boundary, and not, as was at first hoped, a strong vein or bar like those before described. The only exceptional feature met with, whilst sinking the shaft through the metamorphic sandstone underneath the fourth granite-vein, was a vein of white "orthoclase" mixed with some quartz, which commenced at first quite thin right underneath the former vein, but soon thickened to 3-4 inches, and was never lost for the whole distance sunk, dipping nearly vertically through both the sandstone and the granite. It sadly deceived the poor miners for a good while, as they mistook the felspar for quartz, and considered the vein to be a fresh "making" of the reef. After the shaft-sinking was discontinued, it was noticed that the relation of the fourth granite-vein to the reef furnished strong evidence of the latter being faulted by the former; and a cross cut, starting right on the top of the bottom floor of granite, was driven eastward in search of the faulted portion. No signs of the reef being, however, met with after a distance of 70 feet was reached, this work has likewise been discontinued, and it is now contemplated to cross-cut westward — a direction which ought, in fact, to have been tried at first; for, according to the old mining rule, that the hanging portion of a faulted lode has in most cases slid down in the direction of the dip of the faulter, it is the most likely side on which the reef might be regained (fig. 7).

The four granite-veins described have, as mentioned in the beginning, been observed in the mine of the Alliance Company; in the the neighbouring mine of the Speculation Company only the second vein that dips in this direction (southward) has as yet been struck, the first vein lying wholly in the Alliance Company's ground, and the third and fourth occurring at a lower level than the workings in this mine have reached. Lately, however, a granite-vein has been struck in it at a depth of 200 feet, which is evidently quite new, i. e. different from the other four veins, as it has only a thickness of 1-2 feet, dips nearly vertically, and runs obliquely across the reef. It is at present exposed in one drive only; but as the workings progress it will be interesting to observe whether it stands in connexion with the second and third granite-veins, which lie respectively above and below it.

With regard to the mineral character of the granite of the veins, as compared with that of the granite of the main mass in the immediate neighbourhood, hardly any difference can be observed, except that the vein-granite appears to be slightly more quartzose, and to contain perhaps less mica than the other. It can scarcely be doubted that the two lower granite-veins and the bottom floor are still in connexion with the main mass, and would lead up to it if followed northward; whilst the other veins were originally so con-

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