GEOLOGICAL NOTES.

Otago Witness, Issue 1866, 26 August 1887, Page 13

GEOLOGICAL NOTES.

By W. Gbbkn, Ophik, THE RISE-AND-SHINE GULLt.

In the eatly part 'of this year I had the pleasure of inspecting another example 'of ■" gold in the bed rock.'* This deposit occurs on the sunny slope of the Dunstan Range, in the Rise-and-Shine Gully, about five miles from Bendigo. It was discovered about 18 months ago by Mr Abelsted, a-n old friend of mine, one of the Rise-and-Shine company of alluvial miners. As the particulars of this discovery may be interesting to some readers, I will give them here in extensd.

On a former visit to this locality some 15 years ago, among otherplaces of interest in the old working through which Mr'Abelsted led •me was a spot where, it was said, " the yield of the alluvial had been very good." I ob,eerved that the bed rock was decomposed, and showed one or two clay scams cutting through it, giving some prospect of a reef. Here I suggested to my guide that he should sink in the rock, and see if the gold went down with it. However, the hint was not taken at the time, and the circumstance was forgotten by both of us, until of late, when the discovery of auriferous rock was made at Ophir; when, like others, Mr Abelsted came to see this strange formation, and returning home, he recalled to mind the hint given in former years about the prospects of his own locality. Now was the time for action. He sooh trted the spot, and found gold in the bed rock. The rock proving of. a soft, friable nature, the company commenced the operation of sluicing it away in the usual manner, and were thus engaged on the occasion of my last visit as above stated.

The gully which bears this beautiful name heads from a point very near to the top of the range. Its course is about northward. For the first two miles it is rather wide, with little fall till it reaches the " saddle." Here it bends slightly to the left, and descends rapidly through narrow gorges to the plains below in the direction of Bendigo.

The auriferous rock occurs in one of the left-hand branches of the gully, near the head. It is a narrow belt of mineralised argillaceous mica schist, densely charged with iron pyrites. The upper portions of the rock, as also the pyrites, are very much decomposed, and of a sort of chocolate colour. There is at least one line of fissure oa the spot, bearing about N.E. and S.W. The auriferous rock is closely related to this line, whiGh bounds it on the S.E., forming the hanging wall, and dipping in that direction at a steep angle. Tbis fissure is distinguished by a dislocation of the strata and by a band of bluish clay flanked with a few inches thickness of ochery hematite. The workings, which arc from 30ft to 40ft wide, had not yet disclosed a foot-wall. But there seems little doubt that, sooner or later, one will be found. The gold is very fine, and is certainly derived from the decomposed pyrites. Regarding the yield, I am not in a position to say ; but judging from samples tried at the time, so long as the rock continued friable, it should with ordinary appliances be made to pay. The company were sluicing the rock in the ordinary manner, with a tail race and boxes, with matting for saving the gold. The water running away, had the singular appearance of being almost as red as blood. There being little or no quartz in this auriferovis rock, and besides, as it could be easily pulverized, it should be, I think, a good subject for tlie chlorination process. The ordinary country rock of the locality is of the same general character as the gold-bearing portion, and differs little from it in appearance, except in the absence of the decomposed pyrites. Still, the course of this formation across the spur should be no great task to make out, with the fissure line and dislocated strata for a guide.

The reef opened some years ago about a mile farther down the gully is of the same class, except that it is harder, contains more quartz in the laminations of the rock, and the pyrites are undecomposed. The Thompson's creek reef, on the road through the range to Tinkers, is closely allied to these in general character.

It is worthy of remark that all these peculiar reef formations are situated very near the line of division between the' argillites and mica slates of the Kakanui and the mica and chlorite schists of the Wanaka formations of Hutton's " Geology of Otago." The line of junction of these series of rocks, as I have made it out, crosses Thompson's creek on the short track from Bendigo to Tinkers. My reason for referring to this is that these reefs partake of the character of both formations, and that they lie on the margin of a great belt of mineral country. But more of this anon, in another paper. The Rise-and-Shine Company have proved themselves a hardy and energetic class of men, as at their elevation the climatic influences are of no fuean order, and they have laboured on, night and day, through winter storms and summer heat, with varying fortune, for the last 20 years. It is hoped that they will realise a fortune, or at least a competency, for they richly deserve it, as a reward for their endurance and industry; for there are few alluvial claims in this country that work the round of the seasons at the same elevation as this.