135 
There is, however, some difference as to the relative amounts 
of microcline and albite: in the sodalite-foyaite the latter pre- 
vails or both felspars are present in about equal amounts, 
while microcline predominates in the microperthite of the peg- 
matites. 
The felspar crystals of the sodalite-foyaite inclose numer- 
ous minute needles of ægirine and occasionally also of arfved- 
sonite. A peculiar transformation into analcime is observed in 
Fig. 14. Microcline-microperthite of the sodalite-foyaite. 
Section parallel to с (001); crossed nicols; x 150. — The black and the heavy shadowed 
lamellæ are albite; the white and the light shadowed areas are microcline. 
one specimen of the rock: here the microcline is intact but the 
albite-areas of the perthitic crystals are replaced by analcime with 
the exception of a few small remnants now lying entirely im- 
bedded in the newly formed analcime. This analcime shows the 
‘eudnophitic’ double refraction and a distinct cubic cleavage. — 
The felspar crystals are as a rule uninfluenced by ordinary 
weathering; only in a few specimens a slight kaolinization is 
seen, and this has only affected the albite while the microcline 
has remained clear. 
