176 
that the latter rock has a higher ferric oxide and lower ferrous 
oxide. 
Contact facies of arfvedsonite-lujavrite. — At Nunasarnak 
the arfvedsonite-lujavrite passes into a peculiar contact modifi- 
cation directly bordering on the sandstone. This contact facies 
is a very fine-grained or dense rock of a conspicuous banded 
and spotted appearance as described p. 74. Upon microsco- 
pical examination it proves to be of a more acid character than 
the typical lujavrite: nepheline occurs only in small amount 
and in many specimens it is entirely absent while small allo- 
triomorphic anhedra of quartz fill the interstices between the 
felspar-laths. The white bands of this contact rock are almost 
exclusively made up of lath-shaped crystals of albite, some- 
times intermingled with microcline-laths, and there is a pro- 
nounced parallel arrangement of the crystals. The green spots 
are large anhedra of ægirine which enclose a great number of 
felspar-crystals in a poikilitical manner. The black bands of 
the contact rock have the composition and structure of a very 
fine-grained arfvedsonite-lujavrite devoid of nepheline, and in 
some cases they are quartz-bearing. Minute patches of a yel- 
lowish red mineral, probably an iron-oxide, are frequently 
found in all varieties of this rock. Schizolite has been ob- 
served in one (nepheline-bearing) specimen. Of special interest 
is the occurrence of a mineral, which is probably corundum, 
in an apophysis in the sandstone. This apophysis is of the 
white variety with green spots described above. The mineral 
which is supposed to be corundum is in small columns without 
distinct crystallographic form and about 0°5 millimeter long by 
0-1 millimeter broad. They are colourless and optically uni- 
axial with a low birefringence of negative character; the mean 
index of refraction is like that of ægirine. 
