Although gold-bearing rocks exist in more than one locality near Dunedin, there has never been that conspicuous success in working them, which the investor has a right to expect.
As has been stated, an instance of an exceedingly interesting auriferous rock occurs at Harbour Cone, near Portobello, on the Peninsula. Although frequently spoken of as a quartz reef, this is in reality a dioritic rock, richly impregnated with iron pyrites, and apparently occurring in very large quantities. Several attempts have been made to work it, but all have, so far, proved ineffectual. Some years ago trial crushings were made in Victoria, which yielded 7½ dwts. to half an ounce per ton, and other samples from a portion of the deposit a little lower down the hill gave 8 dwts., 1 oz., 2 dwts., and 6 dwts. per ton respectively. Some doubt was felt as to the probability of finding gold in such a matrix, and other samples were tried in Dunedin, all of which yielded the precious metal. In late years, about 1886, another attempt was made to develope the field, but without success. Professor Ulrich, who has examined the locality, describes the deposit as a peculiar, hard, diorite-like rock, the structure being holo-crystalline and medium coarse-grained; the composition triclinic felspar, hornblende, and some quartz with iron-pyrites finely and uniformly impregnated, more especially through the hornblende part. He considers that a whitish mass overlying the crystalline rock is either a decomposition product or more probably a decomposed rock of genuine trachytic type, which has flowed over the other. This is indicated, he states, by the fact that on its line of continuation, only a few feet distant from the shaft, there exists on the hill-side a massive outcrop of a hard rock, which, according to all appearance, is of trachytic character, consisting of a very fine-grained greyish or yellowish-white base, with impregnated crystals of sanidine-like felspar, hornblende not being observable.
Presuming that the rock exists in quantity, and contains a general average of gold, such as has been mentioned, it seems a matter for regret that steps are not taken to thoroughly determine its value; the prospect of finding rich veins of auriferous quartz, such as are usual in the Thames district, would lend an additional inducement. In addition to the above instance, there is at Green Island a series of quartz reefs, known as the Saddle
