Report on the Geology & Gold Fields of Otago
Appendix 5. — The Conroy’s Gully Reef, Near Alexandea
The Conroy’s Gully Reef, Near Alexandea.
To this reef, which has been for a long time deserted, I was kindly conducted by Mr. Warden Simpson, Mr. Coleman, and Mr. R. Poole, of Clyde, who also afforded me all the particulars of its history. It strikes W. 23° N., and dips northward at an angle of near 80°, cutting very flat-bedded, nearly horizontal mica schist, strongly interlaminated with quartz. The walls appear well defined. According to the descriptions given, it averaged in the workings—now more or less fallen in—from six to eighteen inches in width, and consisted of quartz and mullock running side by side in strike, the latter frequently predominating. It has been opened and worked for over six chains in length, but is traceable for twelve to fifteen chains farther. The first workings consisted of small shafts and open cuttings, but afterwards, when some water was struck in the deepest shaft, an adit nearly 600 feet in length was driven in the strike of the reef from the slope towards Conroy’s Gully, but starting so shallow that it required an open cutting over two chains in length, and nearly two more of a tramway, to obtain fall for the waste, and principally, that it lies only 50 feet beneath, the surface at the end. In fact, when it reached so far, a great portion of the Backs had already been worked out from the top. If on this account the adit must be pronounced, to say the least of it, a very injudicious piece of work, it appears still more so on considering that not far in advance of where the cutting begins the slope towards the bottom of the gully suddenly becomes very abrupt, and that it (the adit) might, therefore, have been put in from a point in the latter in the line of strike of the reef, lying at least 150 feet lower, and not perhaps more than 300 feet farther, than where it now commences. After all the Backs above the adit had been worked out, a shaft was commenced in the reef at the far end of the adit, but after sinking ten feet, where water made its appearance, the work was given up, and the reef shortly after deserted. Down the shaft, and left in the bottom, a vein of quartz was followed of six to eight inches in thickness, showing a tendency to widen out, of which the last 25 tons crushed yield 1 oz. of gold per ton. Touching the aggregate of the returns, it amounted, according to Mr. Poole, to £2,005 from less than 500 tons crushed; whilst the total expenditure on the claim, including crushing machinery, tools, &c, was £3,756. The crushing machinery, which stood in the bottom of Conroy’s Gully, close below the line of the reef, was sold to Williams and party, on the Carrick Range, who are there erecting it on a reef claim, to be noticed further on. All accounts agree that a considerable amount of the, in the average, very fine gold, as also of quicksilver, was lost in the tailings, through the crushing and gold saving process not being at all understood at the time. Comparing the great waste of money, through injudicious workings with page 201the total returns, and looking at the above indicated facility with which it could be opened at a good depth, whilst relying on information concerning its character as left underfoot at the end of the old adit, I certainly think this reef deserves another systematic trial.