426 Transactions. 



The mountain presents several difficulties for a geological 

 examination. The surface of the rock composing it is every- 

 where covered with a thick mantle of decomposed rock and 

 vegetable mould, which often renders the nature of the rock 

 beneath a matter for conjecture. The evidence afforded by 

 surface boulders has sometimes to be relied on, and, since they 

 may have rolled some distance, deductions based upon them 

 mav not always be reliable. 



A map showing any topographical features was not pro- 

 curable, and in preparing a map of Harbour Cone and its en- 

 virons it was necessary to first survey it. A contour map was 

 made, the survey being made with aneroid barometer, prismatic 

 compass, and Abney level. The position of all main points 

 was fixed by means of cross-bearings, and contours then run 

 at every 100 ft. from sea-level. 



Two shafts existed in the valley where mining was originally 

 carried on. The lower one was filled with fallen earth and 

 logs, and hence was not accessible. The upper one was in 

 a better state of preservation, but it was only possible to de- 

 scend as far as the first cross-drive, as water had risen in the 

 shaft below. It was thus possible to penetrate only about 

 5 ft. or 6 ft. into the auriferous rock, as will be seen in the sec- 

 tion (Plate XIII). 



It is hard to understand how the auriferous nature of the 

 rock, or, indeed, how the rock itself, was ever discovered. The 

 mountain-sides and all the valleys and stream-beds were care- 

 fully prospected, but no trace of the rock could be discovered 

 on the surface, and the site of the mine renders it improbable 

 that it was accidentally discovered in sinking for water. 

 Panning- off of the creeks showed no colours of gold nor trace 

 of pyrites, nor any other mineral that would point to the pos- 

 sible existence of gold. 



The purpose of this paper is to describe the characteristics 

 and occurrence of the auriferous syenite and associated rocks, 

 and if possible to account for the occurrence of gold in the rock. 

 The occurrence of gold in plutonic and volcanic rocks is a ques- 

 tion bearing strongly upon its presence in lodes and allied bodies, 

 and the occurrence of it in comparatively large quantities is a 

 distinct peculiarity. 



In rock-analysis the methods described by ' Berringer's 

 Assaying " were exclusively used, and in the assay of the syenite 

 for gold and silver the usual fire methods were used. The 

 assays were run with one or two check assays at the same time, 

 and the assays and checks agreed almost exactly. The charge 

 employed was, — 



