464 Macfarlane on the Acton Copper Mine. 



in solution by tlie water, it seems evident that it could not have 

 existed in the water in the state of sulphate of copper, from the 

 oxydation of impregnated copper pyrites; because such a solution 

 on coming in contact with limestone would have formed with it 

 sulphate of lime and carbonate of copper. Nor is it possible to 

 ignore the physical properties of copper pyrites, and suppose it to 

 have been, to however slight an extent, soluble in water. The 

 only solvents known for heavy metallic sulphurets, are the alka- 

 line sulphurets. Many heavy metallic sulphurets when fused with 

 sulphuret of potassium or sodium, yield when treated with water, 

 solutions containing considerable quantities of the heavy metals ; 

 and I have found that on fusing a regulus containing iron, copper, 

 cobalt and nickel, with sulphate of soda and charcoal, and treat- 

 ing the result with water, a dark green solution was obtained, 

 containing, after careful filtration, all four of these metals. This 

 solution, on exposure to the air, gradually oxydized, became color- 

 less, and deposited the metallic sulphurets as a black powder. I 

 am not quite prepared to assert that the copper in the veins above 

 referred to was deposited in this manner ; but I am of opinion that 

 if we are to adopt the theory of secretion from the side rock, this 

 is the only explanation which is admissible. The third theory of 

 the source of the copper is probably the correct one, and it is the 

 one which is most in accordance with generally received opinions* 

 Colta, for instance, regards it as certain that mineral veins proper 

 have been filled up by infiltration, and that the material thus de- 

 posited came from beneath.* If we however attempt to go a 

 step beyond this general explanation, we must enquire as to the 

 nature of the solvent, and in doing so can scarcely arrive at other 

 results than those mentioned in connection with the second the- 

 ory. We must regard the alkaline sulphurets as the most probable 

 solvents under the circumstances ; and when we reflect that the 

 sulphurets of platinum, gold, mercury, tin, tellurium, antimony, 

 arsenic, vanadium, molybdenum, tungsten, nickel and iron, are all 

 soluble in alkaline sulphurets, it will appear that the latter may 

 have played a more important part in the formation of ore veins 

 than has been hitherto supposed. When moreover it is remem- 

 bered, how numerous and diverse the double sulphur salts are, and 

 how many of these, especially arsenic and antimonious sulphurets 



• Cotta; Erzlagerstatten, p. 127. 



