SYSTEMS OF MINERAL VEINS. 413 



expression this may apply to the continent of Europe, though both 

 in the Pyrenees, and around the central granitic tract of France, 

 metalliferous veins apparently originating in these rocks, traverse 

 strata of the oolitic and cretaceous systems. 



Association of Veins and Dykes. It must here be remarked, that 

 both in Great Britain and throughout Europe intrusive veins and 

 basaltic dykes are in the same manner abundant in the primary and 

 rare in the secondary and tertiary strata. This is one of many general 

 analogies tending to substantiate the opinion that rock veins and 

 dykes, and metalliferous veins, ften form two parallel series of 

 products developed during the same geological periods by the same 

 general causes, acting under different circumstances upon different 

 materials. The disruptions by which igneous rocks were placed in 

 contact with secondary and tertiary strata must have been first expe- 

 rienced by the older strata, from beneath which the disturbing force 

 originated ; hence it is easy to understand why the primary rocks are 

 so universally, and the secondary and tertiary strata so partially 

 affected by dykes and enriched with mineral treasures. 



Modern Veins. As an example of veins of more recent date, we 

 may quote Von Dechen's notice of the veins of Joachimsthal. In 

 this case the dykes of basalt which divide the mica slate are them- 

 selves cut through by mineral veins. These dykes are variously 

 connected with great overlying masses of basalt which break into the 

 Brown Coal formation. It is therefore evident that the silver, arsenic, 

 and cobalt ores have been thrown into the veins at a later epoch than 

 that of the brown coal tertiary deposit at the foot of the Bohemian 

 Erzgebirge. 



Werner's Eight Systems. Werner distinguished eight principal 

 systems of mineral veins in the mining field of Freiberg. The first 

 and oldest produces abundance of argentiferous lead glance. It con- 

 sists of coarse granular lead glance with from one and a half to two 

 and a half ounces of silver per quintal, common arsenical pyrites, 

 black blende in large grains, common iron and hepatic pyrites, some- 

 times a little copper pyrites, and a little sparry ironstone. The vein- 

 stones are chiefly quartz, sometimes a little brown spar, rarely calc 

 spar. These circumstances occur most generally in veins ranging from 

 north to south. 



The second yields lead very rich in silver. It contains lead glance 

 in large and small grains ; black blende in small grains ; iron and 

 hepatic pyrites, and a little arsenical pyrites. In addition, dark-red 

 silver ore, brittle silver ore, white silver glance, plumose antimony 

 ore. The veinstones chiefly quartz, with much brown spar and often 

 calc spar. The veins range south and south-west. 



The third yields lead glance with one ounce of silver per quintal, 

 much iron pyrites, a little black blende, and red iron ochre. Vein- 

 stones are quartz, sometimes with chlorite mixed and surrounded with 

 clay. The veins range north and south. 



The fourth yields lead glance with one-fourth to three-fourths of 

 an ounce of silver per quintal, radiated pyrites, and sometimes brown 



