Under any circumstances some natural processes are associated to the formation and filling of gold veins. Even had been the original veins solid masses of gold, silver or any base metal, their contents would have been scattered far and wide through the rocks which were formed out of the earth’s first crust, even if that crust itself did not contain them, and the condition of the rocks would have been one of the first results of erosion, and the formation of gold veins by segregation or substitution must have commenced even in those early days, by the workings of the laws of chemical affinity, which imply the abandonment by one element of its associate in a compound when it meets with another which is more to its linking under suitable conditions for making the exchange.
How easily these changes were performed may be seen in the occasional action of metallic compounds in the orebody. Just as the pyrite is present in many deposits such those of gold gravel deposits, drop to pieces and decay with extraordinary rapidity, so specimens of pyrite of the bronze-colored variety from some places such Monte Cristo district, after remaining in a wooden box only two months, were entirely decomposed, the pyrites having absorbed moisture, which combining with the contained sulphur had produced sulphuric acid, which in its turn had combined with the gangue of the specimen, forming glistening salts and rough concretions, not only on the specimen originally attacked, but on the adjacent ones which happened to be in contact with it. The amount of moisture absorbed may be so great that what remained of the specimens could not be handled without staining the hands black.
This kind of changes can be noted in the vein by extracting samples, and after a time, the gold vein will present a different appearance due to the changes occurred in place. If the small amount of moisture which is present in a dwelling room can affect such changes, it is a good way to understand and accept some changes effected by nature in her underground workshops, with her absolute disregard of the element of time.
Those operations are constantly going on in nature, and there is plainly evident from the changes, which take place in the outcrops of veins and elsewhere. Gold prospectors constantly find incrustations or various salts such alum and those of soda and potash, forming on the sides of caves, and even of other minerals on the walls of deserted mines. Formation, rearrangement, destruction, reformation and return to the original are the perpetual cycle of the changes in veins, and not only of them, but the rocks in which they are contained. These views afford a natural explanation of the reason why gold veins are confined to certain regions and are not found in all areas. But, just as soon as fracturing began, and with it the circulation of heated waters, the concentration of the minute particles into gold veins would begin, which as they in turn were eroded would furnish particles of larger size to the sediments, and in time these might contain sufficient gold bearing minerals to form large deposits when concentrated by the circulating waters, even at long distances from the seat of the original rocks from which the mineral was derived.