181 
some kind of mechanical or chemical process, perhaps also 
they represent a second generation of felspar. The first as- 
sumption is supported by their mode of occurrence since they 
are commonly found in small clusters which are abundantly 
present in some slices (see Fig. 19) but are absent in others. 
It is true that the large crystals are of a perthitic structure 
while as a rule the small ones are pure albite. But this, ap- 
parently, is no serious objection since the large felspar-crystals 
egirine 
eudialyte 
perthitic felspar 
nepheline 
albite 
arfvedsonite 
Fig. 19. Kakortokite (‘white’ variety). Kringlerne. Х 8. 
often have an outer coating of albite. Moreover it is found 
that the boundary of the large felspar-crystals is very irregular 
where the albite-coating is wanting, and not seldom crystals are 
observed showing a half-detached albite-shell, a small stripe of 
arfvedsonite being intercalated between the perthitic nucleus and 
the albite-coating. 
While in the white variety of the kakortokite the black 
minerals are interstitial and have evidently crystallized later 
than the light-coloured ones, the black kakortokite does not 
show any marked sequence of crystallization but all the con- 
