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made up of a microperthitic intergrowth of microcline and al- 
bite; within each crystal the two kinds of felspar alternate in 
short and irregularly bounded lameliæ which are most frequently 
elongated parallel to 6 (010). The microcline shows a very 
fine and irregular twin-structure producing a moire-like appear- 
ance of the sections; one of the individuals of the microcline- 
twins is not infrequently reduced to a number of minute areas 
dotting the other individual. The moire-like twinning prevents 
an exact determination of the extinction-angles; it therefore 
remains uncertain whether the microcline is soda-bearing or 
not. The albite is finely twinned parallel to (010). The perthitic 
felspar crystals are sometimes surrounded by a marginal zone 
of pure albite; small tabular crystals of albite without micro- 
cline-inclusions may also be found. In one specimen of the 
rock some of the angular interspaces between the felspar crystals 
are filled with a clear und coarsely twinned albite of the same 
optic orientation as the albite of the adjacent perthitic crystals. 
The felspar contains minute needles of ægirine and some- 
times also of arfvedsonite. It is always somewhat clouded with 
kaolin-like decomposition products, and the microcline always 
proves more affected by this decomposition than the albite. 
In some specimens of this rock a few, dull white or red- 
dish pseudomorphs are seen which are probably derived from 
nepheline. They consist of zeolites (spreustein). 
The dark-coloured minerals of the pulaskite are always 
allotriomorphic. As a rule both arfvedsonite, ægirine, ægirine- 
augite, and biotite are present, but the relative amounts of 
these minerais show quite irregular variations, although the 
rock, as to outer habit, keeps very constant. In some speci- 
mens from Tupersuatsiak and Nunasarnausak the prevalent dark 
mineral is an arfvedsonite closely agreeing with the typical 
variety found in the nepheline-syenites both as to absorption- 
colours and as to optic orientation (c:a= ca. 14°). It has often 
been partially converted into ægirine of the same crystallogra- 
