182 M. Brongniart on the position 



same as that of Monte Ramazzo, i. e. that this serpentine 

 occurs with, or even in the steaschist and calcareous slate, 

 composing these mountains : for, nothing that I was able to 

 see — nothing brought forward by de Saussure, M. de Hum- 

 boldt, in the notes he communicated to me, and M. Cordier-, 

 prove a contrary disposition. But I abandon this point as 

 yet obscure, in order to throw new light on a position little 

 or imperfectly understood, by determining that of the rock 

 or marble celebrated in the arts by the name of Vert de mer, 

 and which I have named Ophicalce veinee, in my mineralo- 

 gical classification of rocks. 



This rock, which is well exposed to the E. of the village 

 of Lavezara, appears to form part of a mountain composed 

 of serpentine and steaschist, i. e. of the serpentine formation. 



If we recollect that at Rochetta, beneath the serpentine, 

 and immediately above the jasper, we recognised a calcareous 

 diallage rock composed of green talc, whitish petrosilex, 

 a little diallage, and red spots that were in a great measure 

 calcareous ; that this rock is moreover traversed by nume- 

 rous veins of calcareous spar, and if we compare this diallage 

 rock with the Lavezara marble, we shall find the same 

 characters of structure and nearly the same composition, and 

 even the same colours, i. e. white spathose limestone, red 

 steatite limestone, and green talc. Only here, the limer 

 stone is most abundant and the felspar appears to be want- 

 ing, for I cannot affirm that it actually is so. Perhaps from 

 researches that a traveller cannot undertake, it may be dis- 

 covered in some parts of this rock. Led by analogy, which 

 may, in geology, be regarded as a sure guide, at least in 

 the same canton or system of mountains, I do not doubt but 

 that the marble or ophicalce veinee of Lavezara, is a minera-* 

 logical modification of the calcareous diallage rock of Ro- 

 chetta, and that it has exactly the same position ; conse- 

 quently that this rock is, like the diallage rock beneath the 

 serpentine, and above the jasper and calcareo-sandstone 

 formation, and that, far from being a primitive rock, as has 

 been said, it belongs to a later formation, that of thd 



