240 
or rhomboidal outlines. Both forms are generally to be seen 
in each specimen. The length of the crystals is one or two 
centimeters. The width of the rhomboidal slices is a little less 
than half as large, whilst that of the rectangular slices is often 
one third of the width only. Dark-coloured minerals are pre- 
sent in no small quantity; augite and biotite are to be seen 
with the naked eye. 
Microscopic characters. — Under the microscope the rock 
is seen to be built up of the following minerals: apatite, iron 
ore, augite, hornblende, biotite, and alkali-felspar. In addition 
to these a large quantity of olivine and nepheline has been 
found in some specimens, and only in very few cases and very 
sparingly ainigmatite, titanite, and zircon have been found. 
As usual the apatite has been developed in stout prisms, 
and can be found imbedded in all the other minerals. The iron 
ore is in grains or in irregular anhedra sometimes as large as 
2 millimeters in diameter. In reflected light it is black metallic 
and often shows distinct twin-lamellation. 
Olivine occurs rather abundantly in some of the specimens 
from Niakornarsuk, but is lacking in those from Narsarsuk and 
Iganek. The size of the grains does not exceed 3 millimeters. 
In the slices it has a very faint yellowish colour, and often 
contains the very same streak-like inclusions mentioned on p. 
199. The cracks are filled with black disintegration products, 
but on the whole the mineral is very fresh. It is often sur- 
rounded by a border zone of greenish augite. 
The augite which is always the main ferromagnesian con- 
stituent forms allotriomorphic anhedra of a diameter of several 
millimeters. ‘‘Schiller” inclusions in two directions are often 
observed; as a rule, this structure affects only a small portion 
of each crystal. The colour of the augite in most of the spe- 
cimens examined is quite light, grayish-green, but in the va- 
riety of the rock from Niakornarsuk which has been analyzed, 
the augite is grayish-violet and exhibits a slight pleochroism. 
