5Q Formation of Gold Nuggets. 



place of lead salts. This decomposition gives a very simple 

 means of accounting for the oxide of iron, so often found in 

 the nuggets and crystals of gold, the latter especially, as 

 shown by the experiments of the late Dr. Becker, by cutting 

 them in halves, and by their established low specific gravity, 

 and their loss in weight suffered in smelting. 



Finding the brown iron ore of the miocene drifts contained 

 gold, I was led to suppose that though I could not make 

 gold deposit on it, I might succeed in making them deposit 

 together, which was the case. I arranged a mass of sand 

 with chips of organic matter in it, in a vessel, and slowly 

 filtered through it a dilute nearly neutral solution of sesqui- 

 chloride of iron, containing a few drops of chloride of gold, 

 and as it passed through, repeated the dose. This continued 

 for some weeks without any appreciable change taking place, 

 but after some months thin bands of hydrated sesqui-oxide 

 of iron began to form across the mass, about the centre, 

 parallel with the surface. As they increased in size they 

 assumed a botryoidal appearance, like the " ferro-manganese 

 ore " which occurs in the quartz reefs, and in many parts 

 were coated with a bright film of metallic gold. Every 

 further addition of the mixed solution produced another 

 layer of oxide and gold, so that in time it appeared stratified. 

 If the gold had been continued alone after once having 

 started its deposition, the result would have been the same 

 as in the case of the decomposition of pyrites. On the 

 other hand, if the iron solution was in excess after a deposit 

 of gold had been formed, it would have produced what 

 is so often found in the alluvial workings, a nugget coated 

 with iron ore, commonly known as "black gold." 



This mixed solution is one which we would not expect to 

 find in nature, but there is no difficulty in supposing the 

 transfer of gold with iron that would deposit as oxide, 

 even, if we need to introduce carbonic acid. If a solution 

 of sesqui-chloride of iron and chloride of gold are heated 

 together, the whole of the gold, in a very finely divided state, 

 with a portion of the iron as sesqui-oxide, is deposited 

 in a brownish yellow precipitate. 



Though the processes I have described will account for the 

 formation of nuggets, it does not account for the appearance 

 of the gold in pyrites. I have examined about 100 samples, 

 in none of which do I find any tendency on the part of the 

 gold to assume the form of a coating, it being usually in 

 irregular grains, and small octahedral crystals, seldom to be 



