183 
14. Kakortokite, red sheet, Kringlerne, Kangerdluarsuk, S. Green- 
land. Cur. CHRISTENSEN, analyst. 
15. Kakortokite, black sheet, Kringlerne, Kangerdluarsuk, S. 
Greenland. С. Derrersen, analyst. 
A. Calculated mean composition of kakortokite (see p. 184). 
stituent minerals of this rock show a strong tendency towards 
idiomorphic development. 
Chemical composition. — The analyses which have been 
made of the different varieties of the kakortokite are given in 
the above table (see р. 182). No. 13 shows the composition of 
a specimen of the white sheets; No. 14 refers to a specimen 
of the red sheets; and No. 15 to one of the black sheets. It 
will be seen on comparison that the composition of the white 
sheets of the kakortokite is much like that of the lujavrites 
(see analyses No.s 11 and 12, p. 175). The red and black 
sheets show a chemical composition which is very different 
from that of other known rocks. The salient feature of the 
red kakortokite (No. 14) is the extraordinarily high zirconia 
which indicates that eudialyte makes up about one-third of 
this rock. The distinctive characters of the black kakor- 
tokite (No. 15) are the very high iron combined with high 
alkalies and low alumina; this combination is the chemical 
expression of the peculiar fact that in spite of its extremely 
melanocratic character the rock is entirely devoid of iron-ore. 
As shown by the analyses the white, red, and black sheets 
of the kakortokite are so different in chemical composition that 
they would have to be classified under very different heads in 
any quantitative system of rock-classification. Moreover, since 
the individual sheets are of a large areal extention and of no 
inconsiderable thickness, some of them even exceeding ten 
meters in thickness, and since each of them shows a tolerably 
constant structure and mineral composition throughout its en- 
tire mass, they cannot be regarded as ‘Schlieren’ but have the 
