J. SCHETELIG, 



M.-N. Kl. 



The granite-specimens do not macroscopically show signs of squeezing, 

 and therefore they can only have been slightly influenced by stress. The 

 gneiss-specimens on the contrary show a well-marked parallelstructure 

 with abundant mica in the schistoseplanes. 



The specimens prove that the granite is younger than the gneiss, for 

 small veins of the light granite are seen to penetrate the gneiss (Fig. 2), 

 and small wedge-shaped fragments of the gneiss are enclosed in the 

 granite. The small graniteveins are partly parallel with the schistoseplanes 

 of the gneiss. 



Fig. 2. Rock-specimens from Mt. Betty in natural size showing intrusion of the granite 



in the gneiss. 



Granite. The specimens of granite from Mt. Betty are medium-grained 

 to fine-grained rocks of a quite light colour, sometimes nearly white and 

 generally grayish or reddish gray. The light colour is caused by the 

 predominance of the salic minerals, the felspars (both orthoclase and 

 plagioclase) being light coloured and the quartz light gray. The femic 

 minerals occur very sparingly. The chief constituents to be observed 

 macroscopically are: felspar, thick tabular || Joioj and often twinned 

 according to the Carlsbad law, quartz, and sparingly small scales of biotite 

 and muscovite. 



The common type is a true granite (according to the nomenclature 

 of Rosenbusch) with both biotite and muscovite. One sample shows the 

 felspars as prominent constituents with less abundance of quartz. 



The microscopical examination of thin sections has shown the following 

 minerals: potash-felspar (orthoclase and microcline), plagioclase, quartz, 

 biotite, muscovite, apatite, magnetite, pyrite, zircon and titanite. 



Potash-felspar. The original potash-felspar is certainly orthoclase, as 

 shown in one slice. The orthoclase shows microperthitic, spindular inclu- 

 sions of albite and is partly altered into microcline recognizable by the 

 grating structure. Along the borders of the sections myrmekite (= vermi- 

 cular quartz) is not unfrequently shown. In the other slices microcline is 



