COTTA ON THE VEIN-FORMATIONS OF THE ERZGEBIRGE. 27 



On the Vein-formations of the Erzgebirge. By B. Cotta. 

 {Leitfaden ^c, p. 117.) 

 The mineral veins of the Erzgebirge have for a long period, and 

 especially since the time of Werner, been the object of exact investi- 

 gation, and many attempts have been made to divide them into for- 

 mations. A short account of the conditions of these formations, 

 according to the views of H. Miiller, may serve as an example of such 

 attempts. 



The mineral veins which intersect the Erzgebirge in various direc- 

 tions may be reduced to four large chief divisions, essentially distin- 

 guished from each other by their local distribution, their mineralogical 

 composition and their geological age. These groups are : — ■ 



1 . Veins of the Tin-group. 



2. Veins of the Pyritical Silver-group. 



3. Veins of the Barytes, Silver and Cobalt group. 



4. Veins of the Iron-group. 



1 . The Veins of the Tin-group, taken collectively, form a large 

 band from nine to eighteen miles broad, which beginning on the 

 eastern border of the gneiss district of the Erzgebirge, continues, with 

 few interruptions, in a direction from east to west, through the whole 

 Erzgebirge to the Fichtelgebirge ; but in its progress, in consequence 

 of various local conditions, appears more or less perfectly developed, 

 and worthy of being wrought. By far the greater number of these 

 veins have a strike coincident with that of the collective vein-mass, 

 from east to west (Morning and Evening veins), with a dip generally 

 very high, to the north or south. These veins appear sometimes as 

 regular vein-masses from one inch to one fathom {Lachter) thick, and 

 with a pretty rectilinear strike and dip, sometimes only as bands of 

 many smaller parallel veins lying close together, or at other times as 

 a network of veins and fissures crossing each other at various angles. 

 The first form occurs in most of the tin-veins in the district of Geising, 

 Marienberg, Johanngeorgenstadt and Eibenstock ; the second in the 

 veins in the Sauberg at Ehrenfriedersdorf, and in some veins near 

 Marienberg ; the last in the mass of veins {!Stockwerk) at Altenberg, 

 Zinnwald and Geyer. 



A common character of the veins belonging to the tin-group is, that 

 the mass filling them, firmly united to the rock forming the walls, 

 consists predominantly of quartz, with which are conjoined — as vein- 

 stones, felspar, lithomarge, steatite, tourmaline, topaz, apatite, astrite- 

 mica, chlorite, fluor-spar, and scheelite — as ores, cassiterite (tin-ore), 

 mispickel, chalcopyrite, pyrites, black blende, haematite, wolfram, 

 and molybdenite ; along with which also a multitude of non-essential 

 minerals, mostly belonging to younger vein-formations, as barytes, 

 dolomite, siderite, oligon-spar, calc-spar, amethyst, picrohte, nacrite, 

 specular iron-ore, psilomelane, native bismuth, bismuthine, stibine, 

 and uranite, occur in more or less abundance. 



According to the local conditions in which the veins appear, some- 

 times one, sometimes another of these minerals exists in greater abun- 

 dance ; several are often entirely wanting, a circumstance which ap- 



