448 T rn iiMicfious 



Art. XLII. — The Platinum Gravds of Ore.jmhi. 

 By K. A. Farquharson, M.Sc. 



[Read before the ()t(u/o Institute, 2nd AuguM, 1910.] 



With the advent upon the world's arena of modern electrical apparatus, 

 accurate methods of chemical analysis, and improved methods of sulphuric- 

 acid manufacture, the demand for platinum, both pure and alloyed, has 

 gone up by leaps and bounds ; so much so, indeed, that the supply is falling- 

 short of the demand. When we consider this, and also the fact that at the 

 present time one country itself — Russia — supplies over 90 per cent, of the 

 world's annual consumption of the metal, it is at once evident that prices 

 must rapidly increase, and platinum become an article of gTeat commercial 

 value. It has seemed advisable, therefore, not so much from a scientific 

 as from an economic point of view, to investigate the occurrence of the 

 metal in New Zealand. In this investigation attention will, on account of 

 the magnitude of the task, be necessarily limited almost entirely to Otago, 

 though an account will be given as complete as possible of its occurrence 

 in other parts of the Dominion. 



As far, then, as recorded observations go, platinum in New Zealand 

 may, generally speaking, be said to occur as follows : (1) In Auckland 

 Province, in two places ; (2) in Nelson Province ; (3) in Stewart Island ; 

 and (4) in Otago, in two places. 



In Auckland the more notable of the two occurrences may be de- 

 scribed as follows : In 1882, while a shaft in one of the mines of the Thames 

 Goldfield was being deepened from the 540 ft. to the 600 ft. level, a quartz 

 vein was cut which was found to descend nearly vertically. It was also 

 observed that the vein was impregnated with massive pyrites, and, since 

 it is a matter of common knowledge that gold frequently occurs in such 

 sulphide ores, samples of the material were taken and assayed. In the first 

 assay, 200 grains of the crushed and powdered rock were taken, and these 

 yielded bullion to the extent of 0-021 grain. On parting the bullion in 

 nitric acid, it was found to still retain its silvery lustre and appearance, 

 showing that some other metal than gold was present. Several other 

 assays of the stone "were then made, from which varymg values were 

 obtained, the highest being 0-776 grain from 400 grains of ore. This assay, 

 on parting, was reduced to 0-126 grain, or equal to 10 oz. to the ton. The 

 beads obtained from this succession of assays were then put together and 

 qualitatively analysed. The results showed the presence of silver, gold, 

 platinum, and iridium. 



In the continuation of this investigation the metal was found, by assay, 

 in a large reef both at the 540 ft. level and the 600 ft. level, but in very 

 much smaller proportions. Several pockets of tailings from the battery 

 — the result of the crushing of this reef stone — were also washed, and the 

 metal was got in the shape of mhiute grains accompanying the escaped 

 gold. Viewed under the microscope, the grains were usually rounded, but, 

 curiously enough — and, indeed, quite anomalously — many were found to 

 take the octahedral shape, some being beautifully perfect crystals. Further 

 investigation into this occurrence is going on at the present time, and some 

 interesting facts Avill no doubt be shortly brought to light. 



