116 
considerable amount of other minerals of the pyroxene- and 
amphibole-groups. Only in certain varieties of the rock the 
prevalent dark mineral is arfvedsonite, in others both egirine 
and a catophorite-like hornblende are also present. The 
egirine is partly in independent crystals or anhedra, partly it 
is in parallel intergrowth with the arfvedsonite; in the latter 
case the ægirine most frequently makes up the peripheral parts 
of the anhedra enveloping an irregular nucleus of arfvedsonite. 
The catophorite-like hornblende shows brown, green, and bluish- 
green absorption-tints; in sections parallel to the plane of sym- 
metry (010) the angle of extinction с:а varies from 20° to 70°. 
A narrow marginal zone of arvedsonite commonly surrounds 
the hornblende. A fibrous, crocidolite-like mineral in small 
protuberances projecting from the arfvedsonite is observed in 
several specimens. A colourless augite has only been found in 
one specimen. 
SODA-GRANITE OF IVIANGUSAT. 
At the foot of Iviangusat, on the south side of Kanger- 
dluarsuk, the augite-syenite contains numerous fragments of 
sandstone, and each of these fragments is surrounded by a 
zone of soda-granite. The width of the zones is from one half 
to two meters. The detailed description of the mode of occur- 
rence has been given in the preceding chapter (see p. 53), and 
it has been shown that this soda-granite must have originated 
by a process of resorption the augite-syenitic magna having 
dissolved sandstone. The interest connected with this occur- 
rence is greatly added to by the fact that the rock, both mine- 
ralogically and chemically, bears a close resemblance to the 
arfvedsonite- granite of Ilimausak and Narsak. Macroscopi- 
cally the simularity is almost complete, as the dark mineral 
of the Iviangusat rock strongly resembles. arfvedsonite; upon 
closer inspection, however, it proves to be ægirine-augite and 
catophorite. 
