M. Von Buch on Gabbro. ^ 



to be united with hornblende (amphibole), others wish to 

 separate green diallage from schiller spar (diallage metal- 

 loide), and to form two species of them. M. von Buch 

 conceives, from the exterior characters of jade, and above 

 all from the chemical analysis made of it by M. Theodore 

 de Saussure, and repeated by Klaproth, that it ought not to 

 be united to felspar, so long as it is not found crystallized 

 in forms, which shew this union to be necessary. He be- 

 lieves also that the cleavage, and all other observations al- 

 ready made, tend to unite schiller spar and green diallage, 

 3,ud to separate the first from hornblende, and the second 

 from acty oolite (stralstein) ', thus it is preferable to pre- 

 serve the two species, such as they are determined by 

 Saussure. 



Although blocks of gabbro are spread over the Pays de 

 Vaud and the environs of Geneva, the position of this rock 

 was not known in the Swiss Alps. In 1807, M. Struve and 

 M. von Buch found in the valley of Saas, near the village of 

 the same name (in the Haut Valais), an enormous quantity 

 of these blocks, brought down by all the glaciers, which 

 descend from the neighbourhood of Mont Rosa ; ascending 

 towards the glacier of Mont More, by the road of Macug- 

 naga, in the valley of Anzasca, they met with gabbro in 

 place before they reached the glacier. The jade is greyish 

 white, exactly resembling that of the Pays de Vaud, and the 

 diallage of a beautiful green colour, in pieces which are often 

 half a foot long ; the rock contains also small plates of talc, 

 actynolite in little radiated bundles, and red garnets. The 

 gabbro rests on mica slate, and appears to form the summit 

 of the ridge descending from Mont Rosa, and separating the 

 valley of Saas from that of St. Nicolas, nearly as far as 

 Stalden, where it constitutes an enormous cap : this rock is 

 several thousand feet in height, and about two or three 

 German miles in length. No serpentine is found with the 

 gabbro in the valley of Saas, but it occurs in that of St. 

 Nicolas. The heights of Mont-Cervin, and the pyramid of 

 Breithorn, are known from Saussure, to be composed of 

 serpentina. In the Grison mountains, a chain desceudipg 



