109 
ARFVEDSONITE-GRANITE OF ILIMAUSAK. 
The arfvedsonite-granite of Ilimausak covers an area of 
about 164m", south of the highest summits of Ilimausak (see 
map, Pl. II). This granite-body has the form of a heavy sheet 
or stratum, 150 to 400 meters thick. It is overlain by the 
porphyry-sheets which are older than the granite, and it rests 
upon pulaskite and nepheline-syenite which are about contem- 
poraneous with it. South of Tunugdliarfik Fjord erosion has 
only left a small remnant of arfvedsonite-granite which rests on 
the nepheline-syenite near Tupersuatsiak. This remnant is of 
interest because it indicates that the granite has originally ex- 
tended southward across the fjord and has covered the nephe- 
line-syenites round Tupersuatsiak in the same manner as it 
still covers those at Ilimausak. 
Macroscopic appearance. — The arfvedsonite-granite, when 
fresh, is a light greenish coarse-grained rock the main consti- 
tuents of which are easily detected with the naked eye. The 
diameter of the felspar-grains varies from 2 to 4 millimeters, 
the quartz-grains are a little smaller, while the arfvedsonite- 
anhedra may sometimes attain a length of 10 or 15 millimeters. 
As a result of alteration-processes the rock has assumed a light 
brown colour in some places and a reddish or violet-red colour 
in others. A fuller description of the local variations of the 
outer habit has been given in the preceeding chapter (see p. 81). 
Microscopic characters. — Under the microscope the rock 
is seen to be made up of the following minerals: alkali-felspar, 
quartz, arfvedsonite, ainigmatite, and a little ægirine. Occasio- 
nally zircon, pyrochlore (?), and elpidite (?) are found. In those 
varieties which have undergone alteration processes there are 
found several secondary products viz. magnetite (or titano-mag- 
netite), fluorite, haematite, ferric hydrates, and calcite. 
The felspar is in more or less equidimensional grains, 
sometimes also in imperfect crystals giving broad rectangular 
