THEORY OF METALLIFEROUS VEINS. 247 



a multitude of small cracks, with country rock between. These 

 loosened planes become also water-ways, and, by deposit, form those 

 irregulai veins so common everywhere, but especially in the cinnabar- 

 veins of California. Or, again, crust-movements may produce not 

 clean open fissures, but rather planes of shattered rock like fissures 

 filled with rubble. Deposit in such a water-way forms a breccia of 

 country rock, cemented with vein-stuff. Or, again, in certain country 

 rocks soluble in water, especially limestones, the rock is dissolved along 

 the water-way, and the vein-stuff deposited pari passu, giving rise to 

 what are called substitution-veins. In short, once conceive clearly that 

 mineral veins are filled water-ways, and all these complex phenomena 

 solve themselves. Even porous rocks like sandstones, because of their 

 porosity, become the depositaries of vein-stuff, though not in paying 

 quantities, except along lines or planes where water-transit is more 

 easy and abundant. Examples of such deposits are found in the silver- 

 bearing and copper-bearing sandstones of Utah and New Mexico.* 



Thus there seems no longer any room for doubt that metalliferous 

 veins are deposits from solutions in water-ways of any kind, but mostly 

 from hot alkaline solutions coming up through great fissures. It is 

 only the exact chemical reaction which is yet obscure. The work of 

 the geologist is all but complete ; the problem must now be turned over 

 to the chemist. It may be interesting, however, before leaving this 

 subject, to consider separately the auriferous veins of California, and 

 apply to them the principles set forth above. 



Auriferous Veius of California. — Gold is one of the most insoluble 

 of substances, and the occurrence of this metal in veins has always 

 been regarded as a difficulty in the way of the solution theory. The 

 only free solvent of gold is a solution of free chlorine; but this does 

 not exist in Nature. Nevertheless, gold is known to be slightly solu- 

 ble in the salts, especially the persalts of iron. It is also quite soluble 

 as gold sulphide in alkaline sulphides. It is probable, therefore, that 

 the usual solvents of gold are iron sulphates, and especially alkaline sul- 

 phides. There is also a silicate of gold, which, according to Bischof, is 

 slightly soluble under certain conditions. 



There is abundant evidence that the auriferous quartz- veins of Cali- 

 fornia have been deposited from hot solutions. These veins exhibit in 

 many cases the characteristic ribbon-structure. They exhibit also the 

 luater-cavities characteristic of deposits from solutions, and the vacuous 

 spaces, indicating that the solutions were hot. By actual experiment,! 

 the temperatures at which the vacuous spaces disappear, and therefore 

 at which the deposit took place, have been ascertained — being 180°. 



* Cazin, Newberry, etc., Report on Nacirniento Copper Mines of New Mexico. 

 f Arthur Phillips, ibid. 



