350 THE CANADIAN NATURALIST. [Vol. vi ii 



base is always present. More frequently than in the stratified 

 rocks of the Rhenish slate plateau do veins of heavyspar occur in 

 the diabases that intersect them, as for instance in the Ferdi- 

 nand Mine near Hirzenhain (5 cm.), Rehberg neaj Merkenbach 

 (3-5 cm.), Theobald, Pallas and Orion near Burg (3-15 cm), 

 and Rundbaurn near Dillenburg. As the diabases, according to 

 all examinations hitherto made, contain no orthoclase feldspar, 

 the traces of baryta that the careful researches of Petersen and 

 Senfter have always found in the rock can be contained only in 

 their triclinic feldspars. This is all the more probable since Des- 

 cloizeaux has very recently discovered a triclinic feldspar that 

 must be regarded as nothing else than a baryta-labradorite. 



According to this it would always be the baryta-contents of 

 the feldspars that concentrate themselves in the veins of heavy- 

 spar; for the barytic micas have been first discovered by Oellacher 

 in a few places in Tyrol and by me in Salzburg, and therefore 

 cannot yet be taken into consideration here. 



A second important veinstone, which usually accompanies the 

 heavyspar in the Black Forest, is fluorspar. Up to the present 

 time, however, I am aware of fluorspar only at one point in the 

 region of the porphyritic granite, viz., in the Hesselbach valley, 

 near Oberkirch, where there is a vein from 4-9 feet wide. The 

 accompanying minerals, which occur in smaller quantity, are 

 heavyspar and limonite; copper pyrites being observed in only 

 one small grain. The country- rock is in a completely decom- 

 posed condition. In far smaller quantity has fluorspar occurred 

 in the similar rock at the Hermann mine near Goerwihl, not 

 far from Waldshut. 



In the region of non porphyritic granite the fluorspar is no- 

 where concentrated in any quantity in the northern Black Forest. 

 Although it occurs in nearly all the metallic veins, the heavy- 

 spar always predominates, as in the Neuglueck Mine, King 

 David and Daniel, near Wittichen. In the south it occurs ouly in 

 association, for instance with copper pyrites at the defunct 

 Hausen iron smelting-works in the Wiesenthal. Direct points 

 cTappui for judging of the mode of formation of the fluorspar 

 are not afforded by these veins. But even here it must be care- 

 fully noted that the oligoclase and mica of the country-rock of 

 the veins are always equally and much decomposed ; md ferric 

 oxyd occurs in quantity, viz., individually in the S^lbaender, or 

 as the colouring substance of the flesh-red baryta. Similar phe 



