AT 
ENVIRONS OF NORTH SIORARSUIT. 
From the heights of Ilimausak two mountain-torrents rush 
down towards the Tunugdliarfik Fjord (Pl. VI, Fig. 1 and Pl. X, 
Fig. 1). At a height of a little more than 200 meters above 
the sea the torrents unite in a narrow guliy, at the mouth of 
which they have deposited a crescent-shaped alluvial cone or 
fan which is known as North Siorarsuit. Even in dry summers 
the brook which flows out over the alluvial plain is of quite a 
respectable size. 
The mountain slope north of N. Siorarsuit consists of 
naujaite with veins of lujavrite. The veins have on an average 
a dip of 20°—40° towards the south. This mountain slope is 
traversed by a peculiar red-coloured band which is conspicuous 
even at a distance of many kilometers (Fig. 13) and indicates 
a local metamorphism due to pneumatolytical action. Where 
the alteration is but slight, the structure of the original rock 
is well-preserved, but the colour has become brick-red; upon 
closer examination it is seen that the rock has been filled with 
ferric oxide and violet fluorite, and the original mineral consti- 
tuents are altered to a varying degree. The felspar remains rela- 
tively unaltered, but sodalite and nepheline are converted, some- 
times to red spreustein, sometimes to pale-green gieseckite-like 
pseudomorphs; arfvedsonite and egirine are replaced by chlorite. 
Where the alteration is more intense, the original structure can no 
longer be detected, and the rock is throughout transformed to 
zeolitic aggregates, which are filled with fine micaceous hematite 
and with fluorite. The metamorphism is on the whole of a similar 
character to that observed at S. Siorarsuit (p. 63), but at N. 
Siorarsuit ilvaite and epidote are wanting, and the rock has 
become intensely red. What is specially instructive at N. 
Siorarsuit, is the regular form of the red zone (Fig. 13); it ex- 
tends almost like a dyke in the direction У. $. W. to E. N. E., 
thus intersecting the lujavrite bands of the naujaite at an 
