On the Paragenetic Relations of Minerals. 151 



bably have been formed by cementation during the vitriol- 

 essence of iron pyrites, and the accompanying copper pyrites, 

 &c, were influenced by this process of decomposition. Per- 

 haps ferruginous minerals acted upon solutions of sulphate 

 of copper during hundreds of centuries, in the same reducing 

 manner as metallic iron acts in a few moments. The 

 natural cupreous springs of Neusohl in Hungary, Altenberg 

 in Saxony, Biotinto near Seville, &c, afford evidence that 

 such processes of vitriolescence still take place in the depth 

 of lodes. 



There is in the "Wernerian Museum at Freiberg, a frag- 

 ment of metallic copper, in which a splinter of wood is im- 

 bedded, found in " Old Man."* Taking all circumstances 

 into consideration, it is very probable that native metallic 

 copper has been produced by cementation. 



The lodes of the copper formation do not often form druses, 

 and the known succession of their minerals presents no 

 great variety. The derivative products are more numerous . 

 Sometimes, however, the cupreous minerals are accumulated 

 in large masses under peculiar conditions of the lodes, for 

 instance at the points of intersection. Uniform distribution 

 of the ores for considerable distances of length and depth is 

 not frequent. 



At the mine " Junge Hohe Birke" (Saxony), the copper 

 formation is decidedly more recent than the pyritic lead and 

 zinc, especially in the lodes with a south-westerly direction, 

 and where they intersect vertical lodes, and in these latter, 

 where the former lodes adjoin them. The galena of the old 

 formation, especially in masses with a hexaedral cleavage, 

 is imbedded in copper pyrites, iron pyrites, and sometimes 

 in fahlerz. In one instance, these fragments of galena have 

 been found completely converted into fahlerz, with very con- 

 siderable diminution of volume, the individual hexaeders ob- 

 tained by cleavage consisting of a number of small crystals 

 of gray copper united in a divergent manner, so as to form 

 small druses. This pseudomorph is a very remarkable one. 



Near Freiberg this formation is represented by coarse 



* The technical German term for an old working which has been long aban- 

 doned and again resumed. 



