English Summary. 



The Grandiorite of Sogneskollen. 



Sogneskollen is a rounded mountain top (Fig. 3) in the western 

 part of Sogn in Western Norway (Fig. 1). It consists of a white 

 granitic rock. Dykes of this rock penetrate the surrounding meta- 

 morphosed silurian schists and fragments of the same schists are also 

 found in the granite. Thus the granite must be younger than the 

 Silurian and was likely pressed up during the great Caledonian- 

 Scandinavian mountain folding. The minerals of the rock are plagio- 

 clase, microperthite, microcline, orthoclase, quartz, sericite, biotite, 

 epidote, garnet (only found some fe w crystals), titanite and pyrite. 

 The soda-lime feldspars and quartz are predominating, and give the 

 rock a white or grayish colour. The Mg-Fe-silicates occur either 

 in small lenticular masses or they have a linear arrangement. By 

 microscopical investigation we find a cataclastic or in some cases 

 a protoclastic structure, the latter in the massive of Sogneskollen. 

 In some cases we see a false porfyritic structure with plagioclase 

 in a detritus of quartz, orthoclase and other minerals. 



The chemical composition of the rock may be seen from the 

 analysis page 7. On the basis of this analysis I have tried to 

 calculate the mineralogical composition, and I found that the 

 rock contains about 70 % feldspar, 23 V2 % quartz, 6 % Mg-Fe- 

 silicates and V2 % pyrite. There are 14.86 % K Al Si 3 O s , 48.84 

 % Na Al Si 3 8 and 6.23 % Ca Al 2 Si 2 8 ; the plagioclase is 

 consequently the predominant feldspar and is oligoclase, oligoclase- 

 albite and albite. One portion of the feldspar is microperthite 

 and the rest is microcline and orthoclase. 



The Dyke of White Granodiorite in the Island of Svano. 



Svanø is a small island in Søndfjord 17 km. s. of Florø, a 

 small town in Western Norwav- The distance from Svanø to Soenes- 



