Ch. V.] PRIMARY SCHISTOSE ROCKS. 79 



Porsangerna's is a very conspicuous object, and, when seen 

 from Kielvig, appears to be covered with snow. It is, how- 

 ever, only white quartz in thick beds between layers of mica- 

 slate. This quartz is so thinly stratified, that it separates into 

 very large plates, several feet in length, and only a few inches 

 in thickness, like marble tables. The mica-slate abounds in 

 garnets, and in nodules which are harder than the basis ; and 

 are composed of a fine granular mixture of white talc, red 

 garnet, and white felspar. These nodules not unfrequently 

 impart a very singular appearance to the whole rock.* 



The mica-slate of Leuvig contains neither felspar nor gar- 

 nets, but several beds of granular dolomite; and above 

 these beds, and even in the dolomite itself, are great layers 

 of pure tremolite with green mica, like talc.f Von Buch 

 gives several excellent details of the intimate connection 

 and transition of mica-slate into magnesian rocks, which 

 appears to be effected by the change of the mica into talc, 

 and the pure limestones into dolomite. These excellent 

 descriptions, however, are too long to be quoted in this work, 

 and will scarcely bear abridgment. 



The mica-slate also very frequently passes into clay- slate ; 

 that is, into a rock which is very fissile, and of a fine uniform 

 texture : and this change is effected so gradually, that it is 

 difficult to determine where the one begins and the other 

 ends. We shall quote one example from Von Buch, which is 

 also interesting in other points of view. 



" To what formation does the rock belong which predo- 

 minates between the Gundal and Drontheim ? Are we to 

 consider it as mica-slate or as clay-slate ? On the Steinberge, 

 towards Drontheim, downwards, it appears at first sight com- 

 pletely to resemble clay- slate : the rocks are very fissile, and 

 the laminae are not shining, but have dark-coloured scales of 

 mica scattered over their surface ; and these betray the true 

 nature of the rock ; for such micaceous folia are not frequent 



* Travels through Norway and Lapland, p, 287. t Idem, p. 205. 



