72 



combination is ш, «, è, s, P, x{?) (Fig 2, Plate IV); sometimes, 

 besides these, narrow faces of f or ^. All faces in the vertical 

 zone, though very bright, are so strongly striated longitudinally 

 and, moreover, so uneven, that no accurate measurements of 

 the interfacial angles could be made. On the larger crystals 

 the terminal faces F and s are always dull and often very 

 uneven. The vicinal forms x, V etc. belong to the zone [llO, 

 111], the symbol of which is [ll2], and have for limiting forms 

 (no) and (021). The general formula for them is {/г, Ä;, ?j with 

 I = ^^^ . These peculiar forms are represented by faces that 

 are more or less cylindrically curved about the axis of the 

 said zone, and they cannot be determined with certainty. Such 

 vicinal forms also occur, though more subordinately, on the 

 combination edges (110, TTl) and (110, ill). The forms be- 

 longing here are represented by {k,k,l\^ where k'>l. 



The majority of the crystals now described have a thickness 

 of about P™ and a length of o*^"; but individuals measuring 

 2dm {д length and 8*"" in thickness have also been found. They 

 belong to the primary generation, being of the same age as 

 the feldspar, together with which they constitute the pegmatite 

 masses of Narsarsuk. 



In habit the primary crystals are very constant. Only on 

 a couple of specimens have I observed combinations somewhat 

 deviating from the general type. On one of these specimens 

 the small crystals show the combination ш, ô, P, s; the pinacoid 

 of the second order, P, largely predominates here, and the 

 prism of the third order, s, is represented only by small planes 

 (Fig. 3, Plate IV). On the other specimen the form P alone ter- 

 minates the crystals (Fig. 4, Plate IV). 



Also aegirine crystals of secondary formation showing the 

 habit described above have been met with. Such crystals are 

 found in great number at the locality N0.8, where they, to- 

 gether with small feldspar crystals, likewise of secondary origin, 

 rounded, superficially corroded quartz grains, fluorite etc., form 



