J. SCHETELIG. 



M.-N. Kl. 



7 — 8 cm. thick. The rock is fine-grained and the structure apHtic, the 

 content of coloured constituents being very small. Some few visible 

 phenocrysts of quartz and felspar show the passage into an ordinary 

 quartz-porphyry. With the lens are also visible a few minute grains of 

 rose-red garnet, brown specks of limonite derived from pyrite and a few 

 minute flakes of biotite and muscovite. 



Under the microscope are shown very sparingly pyrite, magnetite, 

 apatite and only some few grains of the rose-red garnet; the coloured 

 constituents: biotite and muscovite are met with in small amounts. The 



Fig. 3. Aplitic granite (analysed 1. Mt. Betty. Micro-Photo. Niçois +• Enlarg. 18.5. 



iron-ore is partly secondary, filling cracks in felspar and quartz and the 

 interspaces between the grains. Biotite is partly altered into chlorite, 

 muscovite is the predominating mica. According to estimation from the 

 slice the whole amount of these minerals constitutes i — 1.5% of the rock. 

 The chief constituents : microcline, plagioclase and quartz form 98 — 99 % 

 of the rock. 



Microcline is the only potash-felspar, in many sections showing fine 

 grating structure. The larger individuals often include small rounded grains 

 of quartz, showing in part a simultaneous crystallisation of both minerals. 

 The twinning lamellæ are often broken and bent, indicating incipient 

 mechanical deformation of the rock. 



Interstital crushed grains of quartz showing undulatory extinction are 

 abundant. 



