83 
decay, and the surface is thus full of circular holes. Round 
each spheroid there is usually a light-brown zone of about a 
centimeter in breadth. On examination with the microscope we 
find, that the light-brown zone consists of ordinary lujavrite of 
similar composition to the surroundings, but with the arfved- 
sonite replaced by acmite; the light-coloured minerals. have 
partially been converted to analcime, and this alteration has 
advanced further in the spheroids than in the main body of the 
lujavrite. Furthest out on the western of the two points we 
find some few veins, up to half a meter broad, which contain 
an abundance of steenstrupine crystals and of transparent green 
natrolite. 
At the coast about two kilometers W. 5$. W. of Igdlunguak 
there is a small projecting cliff called Tugtup Agtakôrfia. At 
this locality the rock is an ægirine-bearing arfvedsonite-lujavrite 
which contains numerous fragments and lenses of naujaite. 
The mountain which rises above Tugtup Agtakörfia has the 
same structure up to about 300 meters, but higher up there is 
uniform gray naujaite (Pl. X, Fig. 2). In the lujavrite of the 
rocky shore there are several irregular veins up to half a meter 
in breadth, which mainly consist of a white, fine-grained al- 
bite or at other places of coarse-grained analcime. In these 
veins we find steenstrupine in beautiful erystals, schizolite and 
epistolite; further a number of other, less rare, minerals in 
well-developed crystals, such as arfvedsonite, eudialyte, albite, 
analcime and natrolite; sphalerite occurs in compact masses. 
ILIMAUSAK. 
As will be seen from the geological map, PI. III, the moun- 
tain group of Ilimausak is crowned by a snow-covered plateau, 
1200 to 1300 meters high. The plateau is not very large and 
its flanks everywhere bear the mark of intense erosion, due to 
62 
