MINERALOGY OF CIIA.LANC11US. 1%$ 



many accurate and judicious observations on them in the 

 Journal de Physique, but he has considered them merely 

 "as silver mines. De Bournon, in his mineralogy of Dau- De BoumonV 

 phiny, in the same Journal, has attempted to explain the ^^ n coiiSst- 

 origin of its veins, and given a very ingenious theory for this e m with fact*, 

 purpose ; but unfortunately it is not applicable to the mine- 

 rals of Chalanches. Dolomieu, Faujas de Saint-Fond, 

 Dietrich, Mongez, Guettard, and others, have also spoken 

 of this mountain, but no one has given a general view of its 

 m ; ,;ral substances. 



Before I enumerate and describe the various products Geological 

 collected on the mountain of Chalanches, I shall give a * ketcl1 °* l% - 

 geological sketch of it. It is of the primitive order, and 

 composed of rocks, the base of some of which is simple, of 

 others mixed. The latter are the most numerous, and con- 

 stitute the chief mass of the mountain. The greater part 

 of the veins yet known are found in a micaceous quartz 

 rock, the strata of which dip in general to the south-west, 

 but at an angle that frequently varies. The manner in 

 which these rocks lie with respect to each other is pretty 

 constant. Granite forms the base of the mountain, and is Granite. 

 foliaceous. It frequently partakes of the nature of gneiss, Gneiss. 

 sometimes of that of amphibolic rocks, and frequently of 

 both at the same time. The gneiss and micaceous rocks 

 vary as much in their grain and texture, as in the difference 

 of their constituent elements. These rocks frequently al- 

 ternate with amphibolic rocks ; often they are mixed toge- 

 ther; and still more commonly their association presents 

 itself with all the characters of a granite, in which the mica 

 abounds but little. In some places the gneiss contains iron 

 pyrites, and occasionally calcareous particles, the presence 

 of which is easily discovered by means of nitric acid. The 

 colour of the gneiss varies extraordinarily. Gray, yellow, 

 green, white, black, &c, are its most common tints : but 

 it is frequently of a red, or reddish colour, whence the rocks 

 it forms have been termed burnt. 



About a third of the way up the mountain, and 800 met. Primitive limc- 

 [874 yards] west of Traverse, the last hamlet we meet with st,nc ' 

 before we get into the wood of the mine, we see in the road 

 tkree strata of nriauU?* limestone, whfch alternate with 



granitic, 



