COTTA ON THE VEIN-FORMATIONS OF THE ERZGEBIRGE. 31 



has given occasion to Freiesleben to divide them into not less than nine 

 distinct formations, — (those of Pobl, Glashut, Halsbruck, Anna- 

 berg, Zschoppau, Johanngeorgenstadt, Schneeberg, Oberschlema and 

 Bockau). As a common character may be mentioned the frequent 

 occurrence of barytes, of noble silver-ores (pyrargyrite, argentite, 

 earthy sulphuret of silver, polybasite, stephanite, native silver), and 

 of cobalt ores (smaltine, chloanthite), with which are usually asso- 

 ciated ores of nickel and bismuth (nickeline, rammelsbergite, native 

 bismuth). But in many of these veins the barytes is destroyed and 

 has been expelled by quartz, as for instance in most of the Schnee- 

 berg cobalt veins. With the barytes and quartz there is very often 

 associated also fluor-spar, dolomite and calc-spar, along with non- 

 argentiferous galena, brown blende and marcasite ; sometimes fahlore 

 and chalcopyrite also occur in great abundance. Barer minerals 

 are : siderite, conite, pinguite, pseudo-apatite, glagerite, nacrite, 

 gypsum, kerate, realgar, fire-blende, arsenic-glance, native arsenic, 

 bismuthine, uranite, native copper, cerussite, pyromorphite, stibine, 

 plumosite, galmei, thraulite, stilpnosiderite, psilomelane, specular iron- 

 ore, gotheite, haematite and limonite. 



The texture of these veins is often in layers with repeated sym- 

 metry ; the layers are, however, occasionally broken and again ce- 

 mented together, when the texture appears brecciated. 



In the country round Freiberg the veins of this group consist for 

 the most part of barytes and fluor-spar, and besides fahlore, also fre- 

 quently yield noble silver ores, but on the other hand only very rarely 

 ores of cobalt, nickel and bismuth ; in the veins in the district of 

 Marienberg, Annaberg, Joachimsthal and Johannsgeorgenstadt, quartz 

 has already become much more abundant, and cobalt, nickel and bis- 

 muth ores occur almost as frequently as the noble silver ores ; in the 

 veins near Schneeberg again the barytes is almost entirely expelled 

 by quartz, and the cobalt, nickel and bismuth ores are by far the 

 most predominant. 



The Voigtsberg formation of Freiesleben, developed in several veins 

 in the Voigtland, and especially characterized by chalcopyrite, mala- 

 chite, limonite and siderite, with quartz, barytes and fluor-spar, appears 

 to be only a modification of the group now described produced by 

 local circumstances. 



The veins of the barytes, silver and cobalt group are more recent 

 than those of the tin and of the pyritical silver group. The time of 

 their formation coincides, it would appear, with the period of the ba- 

 salt, as they intersect the basalt, but have been observed to be inter- 

 sected by it on one occasion. 



4. The Veins of the Iro7i-group (Freiesleben' s Rothenberg, Aue, and 

 Schellerhauer formation) form a large zone of veins from five to nine 

 miles broad, which runs along the highest ridge of the Erzgebirge from 

 E.N.E. to W.S.W. Their strike is at right angles to the direction of 

 the zone, or from N.N.W. to S.S.E., and their dip usually very steep, 

 partly to the west, partly to the east. Their thickness is usually from 

 six inches to a fathom, but sometimes even three fathoms. The mass 

 filling them consists of quartz, amethyst, hornstone, iron-flint, barytes 



