J. SCHETELIG. M.-N. Kl. 



The mineral constituents of the tonahtic (or quartz-dioritic) gneiss are: 

 plagioclase, quartz, biotite, zircon, apatite and magnetite. 



Plagioclase (oHgoclase-andesine AboAni) is the only felspar. 



Quartz is abundant. The grains are crushed and show undulatory 

 extinction. 



Biotite is abundant and arranged in parallel bands. 



The other minerals occur as in the granite-gneiss. 



In the granite-gneiss the effect of stress in shown by the crushed 

 quartz-grains, and the bent and broken twinning-lamellæ in microcline, but 

 also by the arrangement of the biotite-scales in parallel bands. True cata- 

 clases are not shown. The structure of the tonalitic gneiss seems on the 

 contrary to be throughout of secondary character. 



In one slice — of a rock-specimen, like the other gneisses in external 

 appearance — the following minerals are found: biotite, niuscovite, quartz 

 and some few grains of garnet and clinozoisite. This rock is a common 

 mica-schist. 



The slice of the above mentioned quartz-vein shows quartz and a few 

 minute scales of muscovite as the only minerals. The structure is like 

 the interlocked structure of the quartzites. 



B. The Rocks from Scott's Nunataks. K. Edward VII Land. 



The rock specimens from Scott's Nunataks collected by Lieutenant 

 Prestrud are the first rocks collected from King Edward VII Land. A 

 great interest is attached to these rocks from a country, the geological 

 features of which have hitherto been completely unknown. 



The rock specimens from this locality belong to the following different 

 groups : 



1. Granite, medium to fine grained of grayish-white to light-gray colour. 

 In external appearance the specimens could not be distinguished from 

 the granites from Mt. Betty. 



2. Granite-pegmatite , coarse-grained with felspars (microcline and plagio- 

 clase), quartz and biotite. 



3. Amphibolite, medium to fine grained, dark-coloured, with abundant 

 amphibole, mica and iron-ore. 



4. Gneiss, fine grained, dark-coloured with prominent schistosity. 



The granite and granite-pegmatite are younger than the amphibolite 

 and the gneiss. The gneiss-samples sometimes show veins of granite and 

 pegmatite. A special feature is the segregation of biotite along the border 



