KONGL. SV. VET. AKAhKMIKNS 1 1 A M >[,l N<! A !;. BAND 29. N:<>. 4. 11!» 



Si()j TiOj AhOa KcjO.; FeO MnO MgO CaÖ NasO K2O KaÖ Sum. 



67,47 0,87 26,13 0,06 2,19 0,21 <>,;■.,, 0,66 Ö,2é 0,39 Ö^fl 100,13. 



With hydro-fluoric acid 36,a per cent of cyanite and rutile were isolated, the miner 

 ralogioal composition of the rock accordingly is aboul 49 parts quartz, 36 cyanite, L3 

 ottrelite, 1 rutile and 1 hematite. — A cyanite schist from west of Bäen contained 40 



per cent of cyanite and the rest quartz, with a little muscovite, hematite and rutile. — 

 The cyanite schists of the western part of the quartzite helt consequently, as they have 

 the cheniical composition of clays, are not shore-deposits like the conglomerate and the 

 pure quartzite of the eastern part of the belt. 



From the structural analyses it may be mentioned, that the cyanite-prisms are brpken 

 or rlexed and never idiomorphic, while the ottrelite occurs in crystals which do not exhibit 

 any pressure phenomena (Fig. 11). The large andalusite-»eyes» of the mica-schists have behaved 

 as rigid particles during the processes of deformation, while the surrounding mäss of quartz 

 and muscovite with small grains of other minerals inclosed has been plastic (Figs. 9 and 

 12). The structure now resembles that of a porphyry with strongly developed fluidal struc- 

 ture and phenocrysts. — The quartz mäss is either composed of small polygonal grains 

 or of larger, comparatively homogeneous and little pressed lenticular-shaped ones, both of 

 which are newly formed (Fig. 10). — The larger tourmalines have also been deformed by 

 the pressure. 



The rocks of the quartzite belt are connected with the conformable nnderlying dense 

 fine-grained gneiss througli beds of mica schists, occurring in the latter, therefore it is 

 possible, that the granite, being younger than the gneiss, is also younger than the quartzite 

 formation. But none of the rocks of the quartzite belt now exhibit any distinct proofs 

 of an original contact structure, the låter tectonic movements having obliterated any older 

 structure and stamped their marks upon them all. 



Amphibolites. 



Rocks composed essentially of hornblende and plagioclase, with the structure of a 

 crystalline schist and not that of an eruptive, occur connected subordinately with all the 

 other rocks of the district, with the exception of the granites. The principal occurrences 

 of them are in twö beds, between the quartzite layer and the gneisses. Of these two the 

 one lies east of or beneath the quartzite and separates it from the dense fme-grained 

 gneiss for a distance of 7 kilometers. The greatest thickness of this amphibolite bed is 

 about 100 meters. The other lies, according to the opinion, expressed by De Geer in his 

 cited works, above the quartzite and forms three parts probably separated by faults, as shown 

 on the map. The rocks of both beds agree closely both mineralogically and structurally, 

 and, as they both occur next to the quartzite, it appears probable, that they form parts 

 of one single bed, older than the quartzite, but which has been folded, so as to enclose 

 it. The correctness of this supposition is strengthened by the fact, that the gneiss on 

 both sides of the quartzite-amphibolite complex is of the same nature. 



