80 GEOLOGICAL ARRANGEMENT. 



green, containing long crystals of vitreous feldspar, appears 

 exposed. It is the real porphyrschiefer of Werner ; and it 

 would bo uimcult to distinguish, in a collection of stouee, 

 the phonolite of Parapara from that of Biliri, in Bohemia. 

 It does not, however, here form rocks in grotesque shapes, 

 but little hills covered with tabular blocks, large plates 

 extremely sonorous, translucid on the edges, and wounding 

 the hands when broken. 



Such are the successions of rocks, w^hich I described on 

 the spot as I progressively found them, from the lake of 

 Tacarigua to the entrance of the steppes. Few places in 

 Europe display a geological arrangement so well worthy of 

 being studied. We saw there in succession six formations : 

 viz., mica-slate-gneiss, green transition-slate, black transi- 

 tion-limestone, serpentine and griinstein, amygdaloid (with 

 pyroxene), and phonolite. 



I must observe, in the first place, that the substance just 

 described under the name of griinstein, in every respect 

 resembles that which forms layers in the mica-slate of 

 Cabo Blanco, and veins near Caracas. It differs only by 

 containing neither quartz, garnets, nor pyrites. The 

 close relations we observed near the Cerro de Chacao, 

 between the griinstein and the serpentine, cannot surprise 

 these geologists who have studied the mountains of Eran- 

 conia and Silesia. Near Zobtenberg* a serpentine rock al- 

 ternates also with gabbro. In the district of Grlatz the 

 fissures of the gabbro are filled with a steatite of a greenish 

 white colour, and the rock which was long thought to 

 belong to the griinsteinsf is a close mixture of feldspar and 

 diallage. 



* Between Tampadel and Silsterwiz. 



f In the mountains of Bareuth, in Franconia, so abundant in griinstein 

 and serpentine, these formations are not connected together. The ser- 

 pentine there belongs rather to the schistose hornblende (hornblend- 

 schiefer), as in the island of Cuba. Near Guanaxuato, in Mexico, I saw 

 it alternating with syenite. These phenomena of serpentine rocks form- 

 ing layers in-eurite (weisstein), in schistose hornblende, in gabbro, and 

 in syenite, are so much the more remarkable, as the great mass of gar- 

 netiferous serpentines, which are found in the mountains of gneiss aud 

 mica-slate, form little distinct mounts, masses not covered by other for 

 inations. It is nut the same in the mixtures of serpentine and granulate* 

 limestone. 



