54 Formation of Gold Nuggets. 



over with rnanganiferous brown iron ore, in which I found 

 gold, though I never could detect any in the pebbles when 

 their surfaces were carefully cleaned. 



What the gold salt was, whether a chloride, silicate, or sul- 

 phide, we have no means at present of ascertaining. And as it 

 may have been in the same solution that deposited the 

 pyrites, which probably contained its iron in the form of 

 protocarbonate with sulphates, it was not easy at first to 

 imagine any ordinary salt of gold existing in the same 

 solution as a protosalt of iron ; but this I find can be 

 accomplished with very dilute solutions in the presence 

 of an alkaline carbonate, and a large excess of carbonic 

 acid, both of which are common constituents of mineral 

 waters, especially in Victoria. This is true of chloride of 

 gold, and if the sulphide is required in solution, it is only 

 necessary to charge the solution with an excess of sulphu- 

 retted hydrogen; in this manner both sulphides may be 

 retained in the same solution, depositing gradually with the 

 escape of the carbonic acid. 



Professor Bischoff has su^o-ested the occurrence of sul- 

 phide of gold in meteoric waters, and by experiment he 

 found that it was slightly soluble in pure water. Once 

 formed and present in the water it is, like all other gold 

 salts, easily decomposed. In an experiment I have made, 

 the sulphide of gold was held in a solution by a small quan- 

 tity of an alkaline bicarbonate. A cube of iron pyrites and 

 a chip of wood were introduced, and in a few days small 

 irregular grains of metallic gold were deposited on the 

 pyrites. What part the organic matter took in the reaction 

 is not clear, but the gold was not deposited in the absence 

 of it. 



In Mr. Chas. Wilkinson's paper, a series of experiments 

 are described in which gold was deposited in the metallic 

 form upon a nucleus, from a solution of the chloride by the 

 reducing agency of organic matter, the nuclei being either 

 gold itself, or iron, copper, and arsenical pyrites, galena, zinc- 

 blende, sulphide of antimony, etc. Organic matter has long 

 been known as an agent for precipitating gold in the metallic 

 state from its solutions. 



B-ose states that oxalic acid precipitates it in metallic lami- 

 m~e. This I have failed to produce. When boiled with a solution 

 of chloride, I got purple and red precipitates, but when 

 allowed to remain at the temperature of the air for some 

 hours, a film of gold floated on the surface of the liquid, and 



