12 



The locality where the rare minerals have been found, is 

 situated at the northern extremity of the plateau of Narsarsuk, 

 at a very short distance from the steep descent towards Tunug- 

 dliarfik, just where this firth sends out its branch, Korok. As 

 shown by Plate IX, it occupies but a small area; the distance 

 between the southernmost point where the minerals were found. 

 No. 13, and the northernmost. No. 8, being scarcely half a kilo- 

 metre, and the breadth from east to west amounting to little 

 more than 100 metres. Outside this small area no mineral 

 of rare occurrence has been found on the plateau of Narsarsuk. 

 Everywhere else the rock is of uniform grain , and pegmatite 

 occurs only in this area. At this locality, as throughout the 

 plateau, the rock is highly weathered or split into pieces of 

 varying size. Most of the minerals hitherto collected here have 

 been found among this loose material that covers the ground. 



This isolated locality of minerals is evidently not a contact 

 formation , for it has no connection with the granite , and the 

 parts of the syenite contiguous to that rock contain no un- 

 common minerals. Nor can it be regarded as a vein-formation. 

 In the vicinity there certainly occur vein-like formations of a 

 syenite distinguished from the usual type syenite by containing 

 as chief ingredients minerals of the amphibole and pyroxene 

 groups rich in iron , on account of which the rock of these 

 veins is almost black in colour. But these vein-like segregations 

 have no visible relation to the pegmatite formations in which 

 the rare minerals occur. 



The pegmatite formations within the area where the min- 

 erals occur are extraordinarily numerous, but, as a rule, the 

 extent of each separate formation is rather inconsiderable. 

 Their form is very irregular. In general they may be designated 

 as more or less spherical ; they do not extend so as to form 

 veins or layers. The chief minerals are microcline and ægirine, 

 which often occur as very large crystal individuals. The crystals 

 penetrate without a regular limit into the normally-grained rock, 



