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phie orientation. This alteration-process begins along the margin 
of the anhedra, and the arfvedsonite may at last become reduced 
to a number of isolated lapped remnants enclosed within the 
egirine. As the conversion has been effected without any 
separation of iron-oxides and as the alteration-product is not 
an aggregate but a single crystal of ægirine the process has 
probably taken place before the final consolidation of the rock. 
In some specimens from North Siorarsuit @gerine is present 
in considerable amount. Some of the ægirine-individuals are 
surrounded by a narrow and irregular rim of arfvedsonite in 
parallel position. The arrangement in this case is the converse 
of that mentioned above. In other specimens from North 
Siorarsuit the prevailing dark mineral is @girine-augite. The 
angle of extinction с:а of this mineral varies from 30° or more, 
in the core, to 14° in the outer zone. This indicates a zonary 
banding due to an admixture of egirine molecules in the outer 
zone, a feature which is frequently observed with ægirine-augite. 
The pleochroism is as follows: — 
a deep green 
b a little lighter green 
c light brownish green. 
A deep brown and strongly pleochroic biotite is observed 
in most of the slices and is sometimes relatively abundant. It 
is always associated with arfvedsonite and magnetite. Fresh 
ainigmatite has not been found, but in several specimens from 
North Siorarsuit pseudomorphs are seen which have probably 
been derived from this mineral. The pseudomorphs are enclosed 
in the arfvedsonite. They consist of an aggregate of magnetite 
(or titano-magnetite) and brown mica. Another kind of pseudo- 
morphs supposed to represent eudialyte are found sporadically 
in some specimens of the rock. They consist of an aggregate 
of colourless tabular crystals with hexagonal outlines and with 
