44 
eudialyte which attain about two millimeters in diameter. Among 
the minor constituents rinkite is seen almost constantly as pale- 
yellow, flat prisms. — In spile of its colour the white kakor- 
tokite is a melanocralic rock-type, but the pure white colour 
of the felspar becomes very prominent owing to the size and 
form of its crystals, and the contrast with the black sheets 
further accentuates the light colour. 
The black sheets of the kakortokite have quite a similar 
size of grain and structure as the white, but the black minerals 
(arfvedsonite and subordinately ægirine) are here quite predominant 
among the constituents of the rock, making in all about two- 
thirds of the whole; the remaining third is felspar, nepheline 
and eudialyte. The eudialyte is here usually brown and not 
fresh. — In addition to these two principal varieties we also 
find very frequently a red kakortokite. This has the same 
mineral components and structure as the white and black sheets, 
but it contains clear red eudialyte crystals in such great quan- 
tities, that the rock is of a distinctly red colour. The red 
kakortokite occurs in sheets between the others; in some of 
the red sheets the black mineral components are almost entirely 
wanting, in others there are just as many of them as in the 
white sheets. 
The white and still more the red sheets are rapidly decay- 
ing, the black somewhat harder. In the slopes of the mountain 
therefore the biack sheets form the vertical walls, the white and 
the red sheets the more level terraces. Seen from a distance 
there seem to be sharply defined contacts between the differently 
coloured sheets, but closer examination shows that this is not 
the case. Thus, if we examine the junction of a white and a 
black sheet, we will observe in the white kakortokite to- 
wards the boundary that the amount of dark-coloured minerals 
gradually increases, and thus a perfectly even transition to the 
black kakortokite is effected; but usually the transitional zone 
only has a breadth of some few centimeters. 
