M. Yon Buch on Gahbro. inf 



M. von Buch observes that the geological position of 

 gabbro is that always assigned by the German geologists to 

 serpentine, and that these rocks are almost always found 

 near each other, and even mixed ; it appears to him probable 

 that serpentine is but gabbro mixed with a great quantity of 

 talc, and in which the constituent parts are, from their very 

 great fineness, no longer distinguishable. He observes, in 

 support of this opinion, that serpentine is not a simple mine- 

 ral, and that it is an error to assign it a place in mineralogical 

 systems, that it contains parts differing from each other in co- 

 lour, fracture, weight, and hardness, and which, where they 

 acquire a visible size, appear as diallage, talc, oxidulated 

 iron, mica, &c. : lastly, that Rose has remarked oxide of 

 chrome as a constitutent part of serpentine, this M. Vauquelin 

 has also found in green diallage. 



The Zobtenberg, in Silesia, described long since as a 

 mountain of serpentine, is entirely formed of gabbro resting 

 upon the serpentine worked at the foot of the mountain, near 

 the town of Zobten. The same rock is found in many places 

 in the county of Glatz, and in the mountain of Herthe, near 

 Frankenberg ; it is composed of white felspar and grey 

 diallage with a little jade, and contains pyrites. M. von 

 Buch confesses that at the time of his travels in Silesia, in 

 1796 and 1797, he considered this rock as formed of felspar 

 and hornblende, though the want of a double cleavage made 

 him even then doubt the correctness of this idea ; and that 

 he had in consequence classed it among the primitive green- 

 stones (diabase, griinstein). Shortly afterwards, the iden- 

 tity of this rock with those of Prato and Genoa being 

 admitted, M. Karsten classed these last also with the green- 

 stones (griinstein) in his Mineralogische Tabellen ; but 

 primitive greenstone, says M. von Buch, is composed of 

 felspar and hornblende ; whereas gabbro is formed of dial- 

 lage, jade, and felspar. The geological position besides of 

 these two rocks is not the same ; confusion will therefore 

 arise if they are called by the same name. 



The town of Vienna is entirely paved with gabbro. The 

 old sandstone and limestone pavements resisted but a few 



