No. 6.] SANDBERGER — METALLIC VEINS. 347 



their great local richness in silver and cobalt (to which farther 

 reference shall be made) rendered them worth mining near Wit- 

 tichen, and gave to them a high value. These veins could never 

 have been worked for heavyspar, as this is always coloured 

 flesh-red (and even brick-red in some places) by finely-divided 

 scales of red hematite. 



These analyses of the fresh granite by Nessler a and of the 

 decomposed by Petersen b. 



a Schapbach, b Wittichen (calculated free from water) 



prove that the baryta still withstands the attack of waters im- 

 pregnated with carbonic acid, when no inconsiderable portions of 

 sodic carbonate, potash, lime, magnesia and ferrous oxide have 

 been already carried off. The baryta is therefore not the oldest 

 vein-stone of the Wittichen veins, but is sometimes underlaid by 

 carbonates. The circumstance that it completely coats and covers 

 the older native silver sheds clear light upon its mode of forma- 

 tion, therefore it was in solution as baric sulphate and not as 

 baric sulphide, which cannot be so easily proved in any other 

 place. Since I could extract soluble sulphates (alkalies) from 

 many granites by means of water, the baric carbonate formed by 

 the active decomposition of the feldspar must certainly have come 

 into contact with them in that form and been precipitated • 

 That it can remain partly in solution along with much alkaline 

 carbonates in waters flowing from the granite is proved by the 

 analyses of the Baden mineral waters springing from similar 

 granite, in which Bunsen has found it along with strontic sul- 

 phate. The deposition of crystalline baric sulphate in one of the 

 canals of tbe Carlsbad wells is known. 



The orthoclase of the gneiss is the most easily attacked, as it 

 occurs in the larger (Carlsbad) twin-crystals in the porphyritic 

 varieties and the larger granitic bands in the region of the Rench- 

 thal, Wolfthal and Kinzigthal. An analysis of the mineral from 

 Vol. VIII. w No 



