238 
stitial between the other minerals. The biotite is present 
in large quantities. It is strongly pleochroic, showing light 
yellow and deep greenish-black absorption colours. The 
ægirine in small grains and rounded prisms is less abundant 
than the biotite. A cancrinite-like mineral occurs subordin- 
ately as small allotriomorphic anhedra. Needles of apatite 
are rare. 
A dyke of syenite-porphyry, about ten meters in breadth, 
traverses the nepheline-syenite on the peninsula west of the 
Korok Fjord, near the northern end of the submarine moraine. 
This is a fresh-looking, grayish-brown rock with numerous 
phenocrysts of felspar (soda-orthoclase), about one centimeter 
long, which are of a form giving rhomboidal or broad rectan- 
gular sections. The ground-mass is fine-grained and of a tra- 
chytoid structure: it is mainly made up of felspar-laths which 
show a marked tendency to parallel disposition. The laths are 
rarely more than one millimeter long and consist of a very 
cloudy microperthite. Besides felspar the ground-mass con- 
tains allotriomorphic anhedra of a brownish-green hornblende 
with an angle of extinction e:c varying from 15° to 25°. In 
small quantities the ground-mass also contains rounded prisms 
of a colourless pyroxene with large angles of extinction. 
Apatite and iron ore occur as minor accessories. This dyke 
is of particular interest because it is the only known instance 
of a syenitic dyke cutting the nepheline-syenites of the Juliane- 
haab district. 
AUGITE-SYENITE OF THE IGALIKO BATHOLITE. 
Occurrence. 
The augite-syenite covers a border about one kilometer wide 
along the western side of the foot of the Igdlerfigsalik mountain 
group, and north of the Korok Fjord it appears again in the 
coast rocks between Niakornarsuk and the mouth of the fjord. 
