206 
The pyroxene is of a lignt brown (not violet) colour and 
constitutes almost half of the rock. It is of the diopsidic type; 
the extinction angle c:c is 38°. The iron-ore forms black 
metallic grains. To judge from the chemical analysis of the 
rock it must be highly titaniferous. No pyrite is seen. The 
olivine is quite colourless and contains small fluid cavities. It 
oceurs in about the same quantity as the iron-ore. The biotite 
is less abundant. It is in irregular grains and is the least 
idiomorphic constituent of the rock. It is strongly pleochroic 
with absorption-tints varying from dark yellowish-brown to 
quite pale brownish. It contains innumerable minute needies; 
these are arranged in three systems intersecting each other at 
angles of 60° and all lying in the plane of cleavage. All the 
constituents are fresh and decomposition products are entirely 
wanting. 
The chemical composition of this rock is shown in the 
above table. The most striking feature is the very high figure 
for titanic acid, in which respect the rock calls to mind the 
ilmenite-norite of West Norway, and the absence of alumina. 
Apart from this the rock shows evident affinities with the jacu- 
pirangite from Brazil, Magnet Cove, and other places. This 
rock is a differentiation-product of foyaitic magmas, whereas the 
Narsak-rock is to be classed with the essexite. As far as I 
am aware no exactly similar differentiation-products from essex- 
itic magmas are known elsewhere, but the pyroxenite from Gran, 
quoted in the table for comparison, appears as a facies of 
essexite and may be cited as an example of a differentiation 
which to a certain degree goes in the same direction as that 
which has produced the magnetite-pyroxenite of Narsak. 
ESSEXITE-PORPHYRITE. 
This rock composes the upper part of the Kakarsuak 
Mountain at Narsak. It is a minor intrusive body of irregular 
shape. It is older than the nordmarkite but is itself intrusive 
