Boult. —Occurrence of Gold at Harbour Gone. 425 



Art. LI. — The Occurrence of Gold at Harbour Gone. 



By C. N. Boult, B.Sc. 



Communicated by Dr. P. Marshall. 



[Read before the Otago Institute, 8th August, 1905.] 



Plates IX-XIII. 



Introduction. 



The occurrence of gold in igneous rocks in New Zealand has 

 been treated of in only one instance — that of the andesites 

 of the Thames goldfields. In these the gold occurred in such 

 small quantities as to require special means of determination, 

 and existed only in the bands of rock immediately next to the 

 walls of the lodes. On the Otago Peninsula, however, it occurs 

 so plentifully in an alkaline syenite that the usual fire methods 

 of assay can be used for its determination. This syenite occurs 

 at the base of a mountain on the Peninsula called Harbour 

 Cone. 



Harbour Cone, as will be seen on the accompanying map, 

 is situated about the centre of the Otago Peninsula, a volcanic 

 peninsula which juts out from the coast of the South Island 

 of New Zealand, here composed of sedimentary and ancient 

 metamorphic rocks. The mountain lies at the back of the 

 settlement of Portobello, and for the last fifty years its slopes 

 have been farmed. It rises on one side from the Otago Harbour 

 and on the other from Hooper's Inlet — a shallow sea-connected 

 lagoon — at first in fairly gentle slopes, and from an elevation 

 of 500 ft. rather steeply to its summit, 1,044 ft. high (trig.). 

 The sides are for the most part grassy, but a portion of the cen- 

 tral cone is covered with bush. The top is composed of a hard 

 cap of solid rock. Its sloping sides and steep central cone 

 give it the typical appearance of a volcano, and popular be- 

 lief has always considered it an extinct one. 



About 1874 the district was startled by the discovery of 

 gold at Harbour Cone. Shafts were sunk and a drive made 

 in a valley to the south-east of the summit, and a five-head 

 battery was erected. However, after a short time it was seen 

 that with the amalgamation process then in vogue profitable 

 treatment of the ore was not possible, and operations were sus- 

 pended. While the mine was being worked it was visited bv 

 Professor Ulrich, who reported very favourably on its prospects, 

 but, despite this, work had to be abandoned. Since then no- 

 thing more has been done ; the battery has been removed, and 

 the shafts been allowed to fall in. 



