92 



marked great masses of primitive saceharoidal 

 limestone, tolerably fine grained, of a bluish tint, 

 and traversed by a great number of veins of cal- 

 careous spar of a dazzling whiteness. These 

 calcareous masses must not be confounded with 

 the very recent depositions of tufa, or carbonat 

 of lime, that fill the plains of the Tuy ; they 

 form beds of mica-slate, passing into a talc- 

 slate # . The primitive limestone often simply 

 covers this latter rock in concordant stratifica- 

 tion Very near the hato the talcose slate be- 

 comes entirely white, and contains small layers 

 of soft and unctuous graphic ampelite %. Some 

 pieces, destitute of veins of quartz, are a real 

 granular graphite, which might be of use in the 

 arts. The aspect of the rock is very singular in 

 those places, where thin plates of black ampelite 

 alternate with thin, sinuous, and satiny plates 

 of a talcose slate white as snow. It would seem 

 as if the carbon and iron, which in other places 

 colour the primitive rocks, are here concen- 

 trated in the subordinate strata. 



Turning toward the West we reached at length 

 the ravine of gold (Quehrada del Oro). We 



* Real talkschiefer of Werner, without garnets or serpen- 

 tine, not eurite or weisstine. It is rather in the mountains of 

 Buenavista, that the gneiss manifests a tendency to pass into 

 eurite. 



f Direction hor. 3*5° j dip 70° South-East. 



J Zeichenschiefer. 



