81 
The transition from the arfvedsonite-granite to the pu- 
laskite was finely exposed to view and proved perfectly gradual. 
The arfvedsonite-granite. — The colour of this rock ex- 
hibits considerable variations. At some places it is light 
greenish, at others white, gray or grayish brown; locally also 
reddish or intensely red varieties are found. But apart from 
this the composition of the granite is very uniform in the 
whole district north-west of North Siorarsuit. The rock is more 
or less coarse-grained, the size of grain being frequently over 
3—4 millimeters; it has a typical granitic structure, indicating 
that felspar and quartz have crystallised simultaneously on a 
large scale; there is no trace of parallel arrangement of the 
constituents, nor of porphyritic or rapakivi-like structures. The 
quartz is grayish clear and occurs abundantly as rounded or 
irregular grains. The felspar grains often have a form which 
gives broad, rectangular sections, but most of them are more 
or less equidimensional and do not show any good crystal 
outlines except where they are bounded by arfvedsonite. The 
latter is as a rule the only dark-coloured mineral which can be 
seen with the naked eye; it occurs in two different forms: 
on the one hand as elongated prisms (1—2 millimeters broad 
and 5—10 millimeters long), on the other hand as broad allo- 
triomorphic anhedra which do not exceed 5 millimeters. At 
some places the arvedsonite is mainly of the latter form, at 
others the columnar form is predominant and the granite has 
then a very different appearance from ordinary granite. From 
the form of the arfvedsonite we can thus distinguish between 
two varieties of this rock, but they seem to occur quite irreg- 
ularly together and transitional forms are very frequent. As 
regards colour, the light greenish varieties represent the rock 
in its freshest condition, and the granite is often uniformly of 
this colour over large distances. Most of the red portions of 
the granite do not seem to have obtained this colour from 
ordinary weathering, but from pneumatolytical action of a similar 
XXXVIII. 6 
