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and melanocratic ones, as most lujavrites. From a systematic 
point of view it would perhaps be more convenient to class the 
melanocratic types as a separate family; in the present descrip- 
tion, however, the term nepheline-syenite is used in the ordinary 
wide sense. The bulk of the Ilimausak batholite consists of 
melanocratic nepheline-syenites, leucocratic types are also re- 
presented though mainly by a very peculiar variety. The different 
types are here described under the following heads: — 
Foyaite 
Sodalite-foyaite 
Naujaite 
Lujavrite 
Kakortokite. 
As mentioned in the preceding chapter the geological ar- 
rangement of these rocks is generally spoken that of tolerably 
flat sheets or bowls placed one upon the other, and the suc- 
cession given in the above enumeration corresponds with the 
actual succession of the sheets. The only exception is that the 
kakortokite is not only overlain by lujavrite but also underlain 
by this rock. It is, however, not improbable that the kakortokite 
was originally the lowermost layer of the whole complex since 
the actual arrangement and shape of the sheets has been modi- 
fied by movements occurring during the final stages of the 
consolidation. 
The uppermost sheet, the foyaite, is quantitatively very 
subordinate. As to outer habit and general character this type 
may be compared with the well-known rocks from Foya. It is 
especially noteworthy that the dark-coloured constituents are 
ægirine-augite and catophorite-like hornblende while ægirine 
and arfvedsonite are the characteristic dark minerals of all the 
other nepheline-syenites of Ilimausak. 
The sodalite-foyaite is a very coarse-grained rock with 
thick tabular felspar-crystals and a considerable amount of 
