134 
5 to 10 times as great as the thickness. Between the felspar 
erystals abundant nepheline and sodalite occur in grains or im- 
perfect crystals measuring 5 to 10 millimeters across; both 
these and the felspars are translucent and of a grayish or 
slightly greenish colour. The dark-coloured minerals, egirine 
and arfvedsonite, are in large allotriomorphic anhedra which fill 
the angular interspaces between the felspathic constituents. 
Eudialyte, of the typical bluish-red variety, occurs abundantly 
in many specimens; it is allotriomorphic against the felspar. 
Microscopic characters. — The main components of this 
rock are the following: alkali-felspar, nepheline, sodalite, arf- 
vedsonite, ægirine, ainigmatite, and locally also eudialyte. The 
number of minor accessories is rather considerable: magnetite, 
biotite, egirine-augite, astrophyllite, rinkite, steenstrupine, poly- 
lithionite (?), and fluorite. Catapleiite, analcime, and spreustein 
occur as secondary products. 
The felspar crystals are microcline-microperthite, as proved 
by their optical properties. They are developed tabular on 6 
(010) and very often twinned according to the Carlsbad law. 
Between crossed nicols they show a microperthitic structure 
which is considerably coarser than that of the microperthites 
of the rocks described above. In sections parallel tu с (001), 
see Fig. 14, the bands of microcline and albite are elongated ~ 
parallel to the plane of symmetry (010). In sections parallel to 
b (010) the microperthitic structure is of the usual habit with 
lamellae at an angle of about 72° with the direction of the 
cleavage. The microcline is twinned according to the albite- 
(or pericline?) law; it never shows cross-hatching but the two 
individuals penetrate one another in a very irregular manner 
(see Fig. 14). The twin-structure of the albite is of the usual 
fine lamellar kind. On the whole the structure is similar to that 
characterizing the felspar of certain foyaitic pegmatites belonging 
to the same complex and described in detail in another place’. 
"1 Meddelelser om Grønland XIV, р. 21 and PI. I (1894). 
