I9I5- ^'o. 4- 



REPORT ON ROCK-SPECIMENS. 



13 



between the amphibolite and the intruded pegmatite, probably produced 

 by pneumatolytic agents from the intruded granite-magma, afterwards 

 solidified as the pegmatite. The relative age of the ordinary granite and 

 the granite-pegmatite was not indicated by the specimens. 



Granite. The granites from Scott's Nunataks are as mentioned medium 

 to fine-grained. The color is chiefly light gray, sometimes gra^'ish-white 

 or reddish-white, according to the color of the felspars. The quartz is 

 gray. The coloured constituents : biotite and muscovite are sparingly 

 present. Two of the specimens show the border between the medium- 





Fig. 4. Rock-specimens from Scotts Nunataks showing the junction of the light medium- 

 grained granite and the fine-grained gray granite. (Natural size.i 



grained light granite and a darker gray, fine-grained granite, which contains 

 a greater amount of biotite (Fig. 4I. It is seen from the specimens, that 

 the light granite is the younger. 



The common type is a true granite with both biotite and muscovite. 



The microscopical examination of thin slices of the granites has shown 

 the following minerals: orthoclase, partly altered into microcline, plagioclase 

 (oligoclase and albite), biotite, muscovite, zircon, apatite and magnetite. 



The potash felspar is in the slices of the common t\'pe usually 

 orthoclase, shown in broad laths twinned according to the Carlsbad law. 

 Microperthitic spindules of albite are not uncommon. An incipient alteration 

 into microcline with grating-structure, is shown here and there in the 



