24 



are tolerably bright. The hexahedral corners are somewhat 

 rounded. Distinct cubic faces have not been observed. 



7. Calcite. 



Pure carbonates are somewhat rare on Narsarsuk. The 

 most common is calcite, which, however, occurs very sparingly. 

 On a specimen which was found lying loose among the gravel 

 near the locality No. 7, the spaces between the aegirine crystals 

 were filled with coarsely spathose calcite, of which, however, a 

 good deal had weathered away, so that the aegirine crystals 

 were in part laid bare. Usually the calcite on Narsarsuk occurs 

 crystallized, though the crystals are always small in size. 

 Crystals of four different types have been observed. 



Crystals of the first type show the fundamental rhombo- 

 hedron, generally alone (Fig. 9 Plate I), Sometimes also the 

 hexagonal prism is present as a narrow truncation of the 

 middle edges of the principal form. The crystals are generally 

 only a few millimetres in diameter and occur as druses ; but 

 single individuals a centimetre or two in size have sometimes 

 been observed. The faces are generally but faintly glimmering, 

 and the crystals seem to be somewhat weathered superficially. 

 This weathering has frequently followed the cleavages of the 

 mineral, so that striations and furrows along them are distinctly 

 observable. The crystals show a brownish tarnish, probably due 

 to some manganiferous substance. Also their interior is usually 

 not quite white, but shows a greyish or yellowish tint. Calcite 

 crystals of this kind have been found chiefly at the locality 

 No. 3. 



Calcite crystals of the second type are acutely scalenohedral 

 (Fig, 6, Plate I). They show only the positive scalenohedrou 



ç=^{437l}. 



The faces of this form are rather uneven, so that exact 

 measurements of angles are impossible. However, the form is 

 fully determined by the following values 



