96 
towards the W.S.W. The essexite is also found at two places 
without any apparent connection with these localities, namely, 
six kilometers north-east of Narsak within a small area on the 
southern side of the valley which leads from the Narsak Glacier 
to Panernak Bay, and secondly about 23 kilometers north-east 
of Narsak on Kangerdluak Fjord (PI. Ш), where the Algonkian 
granite is cut by a dyke of essexite several hundred meters 
wide. 
General appearance. — The essexite decays so rapidly 
that it gives rise to rubbish-covered areas quite bare of vege- 
tation, whose uniformly gray colour makes them conspicuous 
even at a distance. The rock is coarse-grained and of a well- 
pronounced ophitic structure. The main constituents are a 
felspar with conspicuous twin-lamellation and tabular form; the 
length of the crystals is usually 20—30 millimeters, the thick- 
ness about 2 millimeters. Its colour is clear grayish or with 
incipient weathering white. Black allotriomorphic augite, brown 
biotite, and magnetite occupy the interspaces between the fel- 
spar crystals, and in most varieties olivine is detected with the 
help of the lens. Epidote is commonly present as an alteration- 
product. 
As a rule the felspar tables are not arranged in any def- 
inite order; in some cases, however, they show a strong ten- 
dency towards parallel disposition, as a result of fluctional 
movements of the magma before the final consolidation. Here 
and there we find very coarse-grained portions of 10—30 
meters in extent, where the felspar crystals reach up to 6 
centimeters in length and 6 millimeters in thickness. Judging 
from their size of grain we might be inclined to consider these 
portions as essexite-pegmatite, but in most cases they look like 
large clots and often consist almost entirely of felspar; it is 
probable, therefore, that they represent early segregations of 
the magma. In some of these very coarse-grained portions the 
dark minerals have been dissolved and in the cavities thus 
