Wellington Philosophical Society/. 409 



of pyrites has been long familiar both to scientific observers and practical 

 miners, and I remember in 1860 specimens of quartz were given to me in 

 California having cavities left by the decomposition of cubic pyrites, and which 

 contained only a brown powder of oxide of iron and thin films of gold, as 

 showing that the pyrites and not the quartz was the true matrix of gold. 



This view, however, has not proved to be the correct one, the gold having 

 been shown to be an after deposit to the pyrites, and, as Mr. Skey has been 

 the first to explain, due to its direct reducing influence. It appears that in 

 the first place my friend Mr. Daintree, who is now Agent-General for the 

 Colony of Queensland, at the time he was on the geological survey staff of 

 Victoria, pointed out that a nucleus of gold, when placed in a solution of 

 chloride of gold undergoing decomposition by organic matter, is increased in 

 bulk by a deposit of 2)ure gold. Following up this hint, Mr. Wilkinson, also 

 a Victorian chemist, found that many other substances, chiefly metallic 

 sulphides, would also act as nuclei, but that quartz does not do so ; and Mr. 

 Cosmo Newbury afterwards indorsed the correctness of these results. Tn this 

 state of the question Mr. Skey took up the subject, and by a series of 

 experiments, which are detailed in our Transactions, proved that the organic 

 matter is not at all necessary to produce the reduction of the metal, but that 

 it is due to the direct action of the sulphide, and showed that each grain of iron 

 pyrites, when thoroughly oxidised, will reduce 12^ grains of gold from its 

 solution as chloride, which is a proportion far beyond that which could be 

 effected by the same weight of organic matter. He also included salts of 

 platina and silver in this general law, and demonstrated that solutions of any 

 of these metals traversing a vein rock containing certain sulphides would be 

 decomposed and the pure metal deposited. 



We are thus enabled to comprehend the constant association of gold, or 

 native alloys of gold and silver, in veins which traverse rocks containing an 

 abundance of pyrites, whether they have been formed as the result of either 

 sub-aqueous volcanic outbursts or by the metamorphism of the deeper-seated 

 strata which compose the superficial crust of the earth. 



Still following the same line of induction, Mr. Skey has also shown by 

 very carefully conducted experiments that the metallic sulphides are not only 

 better conductors of electricity than has hitherto been supposed, but that when 

 paired they are capable of exhibiting strong electro-motive power. Thus, if 

 galena and zinc-blende in acid solutions be connected in the usual manner of a 

 voltaic pair, sulphuretted hydrogen is evolved from the surface of the former, 

 and a current generated which is sufficient to reduce gold, silver, or copper 

 from their solutions in coherent electro-plate films. 



By pairing the different metallic sulphides Mr. Skey was further able to 

 construct a table of their relative value as electro-motors and conductors 



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