58 Formation of Gold Nuggets. 



same sample made by the ordinary fire assay, and finding 

 that they agreed. 



If sulphide of gold has existed in the metallic waters, we 

 might expect in some cases to find it, but, as before noticed, 

 it is so easily decomposed, that it is not possible for much 

 to have resisted the heat caused by the basaltic eruptions. 



I have experiments now in progress which contain the 

 sulphides of iron and gold in solution, but up to the present 

 time without any result, in this direction. Like some of the 

 others I have spoken of, they may require a year or more 

 to accomplish the end wished for. 



Professor Bischorf suggests silica as the medium for the 

 transmission of gold to the quartz reefs, goid, as he points 

 out, certainty has a great affinity for silica, always being 

 found in connection with it in mineral veins in the drifts, 

 and even in the pyrites, where I have always found silica 

 as grains, and minute nearly perfect hexagonal crystals ; 

 the occurrence of which I have always been at a loss to 

 account for. 



The Professor's experiment is a very instructive one. He 

 reports it as follows : — On adding to a solution of chloride 

 of gold a solution of silicate of potassa, the yellow colour of 

 the former disappears. After half an hour the fluid turns 

 blue, and in time a gelatinous dark blue precipitate appears, 

 which adheres firmly to the vessel. Alter the lapse of some 

 days moss-like forms are to be seen on the surface of the 

 precipitate like an efflorescence ; on exposure to sunlight, no 

 reduction takes place, but after the lapse of some months, 

 if the precipitate is allowed to remain undisturbed under 

 water, a decomposition takes place, and in the silicate of 

 gold appear minute partly microscopical specks of gold. 



If this is the method by which the gold reached the lodes, as 

 the Professor argues, the origin of the silica may also be that 

 of the gold. The origin of the former we now believe to be 

 the silicates of the rocks, by the decomposition of which by 

 mineral waters the silica is conducted to the lode cracks. 

 In these silicates we have therefore to look for gold ; and it 

 is possible that it is contained in them as silicate. To prove 

 this is almost impossible, for if w r e even found the gold 

 it would be in a quantity too small to determine whether 

 it was in combination or not. 



Silicate of gold is extremely insoluble in water, but if 

 we assume that its solubility is in the same ratio to the 

 solubility of silica as the gold of even our richest reefs is 



