Granitic Rocks of Mont Blanc. 1 15 



Another circumstance surprised me much ; this was to see, 

 among the debris proceeding from the mass itself of Mont 

 Blanc, the granitic rock associated with many others often 

 extremely schistose, and the greater part talcose ; even ser- 

 pentine is met with, as also masses of actynolite, a substance 

 almost solely belonging to this kind of rock. The true 

 granites of other countries are, on the contrary, nearly with- 

 out mixture, without any other subordinate rock, and they 

 never, or nearly never have, a tendency to the schistose 

 texture. Lastly, the granite which forms such considerable 

 masses in other chains, appears to me very scarce, and 

 greatly divided in the Alps. There are no doubt chains of 

 mountains without granite ; but from analogy, it is extraor- 

 dinary that true granite should shew itself in such an ele- 

 vated chain without occupying a greater space, or at least 

 without appearing more frequently. 



All these irregularities (many times verified), joined with 

 other circumstances, inclined me to suspect, as I have an- 

 nounced in another memoir (Journal des Mines, No. 137), 

 that the granites and other primitive rocks of the Alps, at 

 least from Mont Cenis to St. Gothard, appeared less ancient 

 than the other primitive rocks ; a conjecture which has been 

 adopted by M. von Buch. 



Without having the intention of at present attacking in a 

 more positive manner the priraordiality of the rocks of the 

 Alps in general, I shall venture to undertake not only to 

 confirm by new considerations the doubts already raised 

 with respect to the granitic rock of Mont Blanc, but to shew 

 that it is not a true granite, either mineralogically, nor 

 geologically, and that in these two respects it appears to 

 unite itself, by different gradations, to a talcose rock widely 

 spread in the Alps. 



If I am not able entirely to convince naturalists of this 

 approximation, I hope at least that they will acknowledge 

 that it very well explains the irregularities that the granitic 

 rock of Mont Blanc presents, compared with the true gra- 

 nites of other countries. The talcose rock whiih I have 

 observed to possess relations to the granite of Mont Blanc^ 



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