crystals are richer in potash-felspar, whilst the peripheric por- 
tions approximate more to pure albite. A cryptoperthitic diffe- 
rentiation is also to be seen very frequently. Minute pulverous 
inclusions, giving a dark colour to the mineral, have been found 
in the felspar in some specimens of the augite-syenite from Nia- 
kornarsuk. In nearly all the specimens of this rock the felspar 
is fresh, or only a little clouded by reason of disintegration 
products. 
Nepheline is entirely absent in some specimens, but gener- 
ally it is present in considerable quantities. It is partially 
interstitial, and partially in micrographic intergrowth with the 
felspar. As a rule it is fresh; in some cases, however, it has 
partly changed to muscovite. 
The structure of the rock is typical hypidiomorphic, and 
presents nothing very particular compared with the augite- 
syenite from other places. But it is worth mentioning that al- 
though the dark minerals are often grouped together as in 
other syenites of the Larvik type, this feature does not approxi- 
mately come out so strongiy in this augite-syenite as in that of 
Kangerdluarsuk (p. 189). 
Chemical composition. — Specimens were taken for ana- 
lysis of the very fresh augite-syenite from Niakornarsuk on 
the north western side of the Korok Fjord. The minerals in 
this variety of the rock are felspar, violet augite, some olivine, 
and iron ore, and very small quantities of brown hornblende, 
biotite, and apatite. As most of the varieties of the Igaliko 
syenite differ from the specimen analyzed in not containing 
olivine, it is probable that the general composition of the rock 
is a little more acid than that of the variety analyzed. The 
result of the analysis is given in No. 26 in the table annexed. 
As a comparison is stated the analysis of the augite-syenite of 
Kangerdluarsuk and of a larvikite from Norway. 
The Korok augite-syenite, as will be seen from the table, 
shows a rather close conformity to that of Kangerdluarsuk, and 
