180 
A brown biotite has been observed in almost all the slices; 
it is in scattered small scales or more rarely in elongated small 
prisms, and its total amount is very small. Ainigmatite is 
sometimes rather abundant, but in many specimens it is en- 
tirely absent. It has not been found in the black variety of 
the rock. inkite which is always accompanied by fluorite 
often occurs in small amount. Æpistolite! has been observed 
in the slices of the analyzed specimen of the red kakortokite 
(analysis No. 14). It is in aggregates of small scales not ex- 
ceeding 0:1 millimeter in length. This mineral is colourless 
and resembles muscovite but differs in the angle of extinction 
(@:¢ == са. 7°). Analcime is rare; only in the black variety of 
the rock it has occasionally been found in noteworthy amount 
filling small interstices between the other minerals. Hydro- 
nephelite and natrolite are common alteration-products of nephe- 
line and sodalite. 
Structure. — As set forth more fully in the preceding 
chapter the entire kakortokite-mass consists of a large number 
of sheets of alternating white (or gray), red, and black colour. 
In the ‘white’ sheets the prevailing minerals are felspar and 
nepheline, in the red sheets the eudialyte is the chief consti- 
tuent, and the black ones abound in egirine and arfvedsonite. 
All the sheets are coarse-grained, markedly miarolitic, and of a 
pronounced foyaitic structure due to the tabular form of the 
felspar crystals. A less conspicuous, though very peculiar, 
feature is the frequent occurrence of a subordinate amount of 
very small felspar-crystals which are not connected with the 
ordinary large felspar-crystals by any kind of transitional forms. 
These small felspar-crystals, are commonly included in the large 
arfvedsonite-anhedra, and their formation, accordingly is prior 
to the final consolidation of the rock. Perhaps they must be 
regarded as fragments detached from the large felspars by 
1 See О. В. Вобсио, Meddelelser om Grønland XXIV, р. 187 (1900). 
