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Report on the Geology & Gold Fields of Otago

Appendix 3. — The Gabriel’S Gully Beef, Lawrence

Appendix 3.
The Gabriel’S Gully Beef, Lawrence.

Amongst the once celebrated reefs of the Province, this is perhaps one that most disappointed its original proprietors, though there are still some who believe in its being worth more than generally supposed, and who occasionally brave the dangerous character of the old working, by putting in prospecting drives at favoured places. I inspected what was accessible of the old workings, in company of Mr. Warden Carew and Mr. H. Squires, legal manager of the old Company, to whom I am indebted for all particulars concerning the character and behaviour of the reef, of which latter itself nothing could be seen. It lies at the head of a small gully running from the N.E. into Gabriel’s Gully, and was discovered by a party working the alluvial at that place. The first workings, by open cuttings and shafts, extend for about 240 feet from the northern hill slope across the gully, a short distance up the opposite slope, and it was from them that the best returns were obtained. Afterwards, to ease the work, the reef was opened at 50ft. in depth, by an adit of 215 feet in length, starting lower down the page 196gully; and 120 feet below this again, a second adit, about 1200ft. in length, was driven for the purpose, both of opening it at that depth, and also to prospect for another reef supposed to exist beyond. This adit, which I inspected, proved unsuccessful in both points. It ought to have intersected the reef under notice at about 900 feet in, but only a thin, slightly auriferous casing was struck there, which, on being followed by a crosscut on the left of the adit, was found to bend flat and run out in the line of dip of a black carbonaceous bed, interlying common hard phyllite. Several small drives in different directions from the crosscut disclosed also no sign of the reef, but it was proved by a winze, sunk in the latter from the upper adit to the level of the lower one, which it strikes in the crosscut a few feet in, that the quartz runs completely out into the just mentioned casing, within about 20 feet above the crosscut, Judging from the surface workings, the reef strikes N. 15° E., and dips westward at 70-75°, crossing soft phyllite, striking N 30° W.. and dipping westward at 30-35°. Its thickness ranged from a few inches to 12 feet in the upper adit workings, and the walls were very well defined, the hanging one showing a thin ferruginous casing. The gold occurred in a shoot extending from near the top of the northern hill (where the reef runs completely out into the hard phyllite) to the end of the workings on the south, and, though at first shallow, deepened rapidly in depth to about 53 feet down the winze, between the two adits. At the south the reef was found to be displaced by a slide, and on recovering it again about five feet out of its previous line, it soon became poorer, broke, and thinned out. The quartz containing the gold, i.e., that within the shoot, was of a soft, ferruginous character, whilst below it a hard bluish stone came in, in which no gold could be seen. Except low down the winze, as above mentioned, and on the north and south in strike, this bad stone was nowhere lost underfoot in the upper adit workings. Regarding the yields, the stone from the shoot, though in places carrying at the rate of perhaps several ounces of gold per ton, paid in the average only 4 or 5 dwts. per ton; yet in spite of this low yield, the mine paid a handsome sum in dividends. The crushing machine of the Company, lately removed to the Blue Spur for crushing cement, stood at the lower end of the small gully, and consisted of two fine batteries of five heads of revolving stamps each, with common copper-plate tables, and blanket strakes attached—a turbine supplying the motive power.

In reviewing all the different points of Mr. Squires’ information concerning the extent, lay, and character of the reef, I think there is a strong probability of the latter representing a large block which dips at a rather steep angle southward in strike, passing the lower adit over head, and lies therefore on its right hand side, not perhaps far off, where it would be advisable to search for it by a branch drive. For the hard blue quartz overhead, and likely to continue downward, and which owes its color mainly to a dense im-page 197pregnation of minute particles of pyrites, has not at all a bad chance of containing a payable shoot, judging from assays of specimens made for me by Mr. Morley, at the Melbourne Technological Museum laboratory, which gave at the rate of 14 dwts. of gold per ton.