31 



those found by Vrba, but owing to his confusing, somehow 

 or other, the pyramids of the first and second order, he cal- 

 culates one more axial ratio. 



The material described by G. Nordenskiöld was found 

 in only very small quantity, as has already been stated, in the 

 Lützen collection. At the locality, however, it is by no means 

 of rare occurrence. It is found there only crystallized, and the 

 crystals are mostly rather small in size. Individuals measuring 

 j_9mm ij^ length and 0,5™"" in thickness are most common. 

 These crystals are often grouped into loosely coherent aggre- 

 gates which sometimes cover comparatively large portions of 

 the surfaces of other minerals as aegirine and feldspar, and 

 sometimes fill the spaces between the crystals of other minerals. 

 Not infrequently, however, crystals 1'=" in length and thickness 

 are met Avith. These larger crystals generally consist of a con- 

 siderable number of smaller individuals grown together in pa- 

 rallel position. The largest crystal aggregation of this kind that 

 has been found is б*^"" in length and З"^"" in thickness. 



Like G. Norden skiöld , I have found all crystals of this 

 mineral that I have examined, of trigonal (rhombobedral) 

 development. Holohedral hexagonal crystals, such as the pari- 

 site crystals from Muso are said to be, 1 have never found. All 

 the crystal faces on the Greenland mineral, except the base, are 

 more or less dull; on the goniometer they generally give only 

 shimmering reflexions. They are, besides, almost always deeply 

 striated horizontally, w-hich also makes the results of the angular 

 measurements uncertain. Therefore the values obtained by me 

 can at the most only serve to identify some forms, but are 

 hardly suitable for an accurate determination of the axial ratio. 

 However, the better among the values found by me agree more 

 with those found by Vrba than with the older ones of Bun- 

 sen and Des Cloizeaux, and therefore the axial ratio calcul- 

 ated by Vrba is given here also for the Greenlandi mineral: 

 f/, : с == 1 : 3,36456. 



