These veins penetrate the crystalline schists, particularly the gneiss, in those localities where the latter are largely penetrated by porphyry. They also generally penetrate the porphyry; only a few exceptions from this rule serving to show that the porphyry-eruptions continued into the period of the formation of the ore-veins. These veins form three or four principal groups, according to their direction, which groups in general differ both in age and in contents. Still, all veins by no means show similar directions in connection with similar contents, or the converse, only these predominant characteristics often coincide. Veins of distinctive contents are almost as much confined to certain localities as they are characteristic of definite directions. According to the contents we can distinguish three or four paragenetic combinations of different ages, but which often extend into one another in such a manner that one fissure sometimes contains the products of two or three of these different periods.