126 



make an angle of 51° 16' with each other. The twin crystal is 

 attached to a small specimen in such a way that the crystal 

 cannot be detached without being injured. However, the size 

 of the specimen itself is so small that it could be placed on 

 the goniometer for the measurement of the angles. The values 

 obtained are as follows : 





Measured 



Calculated 



a 



: a = 50° 47' 



51° 16' 



m : 



:m = 32° 15' 



32° 24' 



Neptunite of type И has been found only at one place, 

 namely the locality No. 2 on Narsarsuk. After a thin layer of 

 loose gravel had been removed, the rock was found to be 

 pegmatitic and traversed by numerous cracks. At first several 

 large aegirine individuals were obtained by breaking into the 

 ground ; at the same time a drusy cavity was laid bare con- 

 taining a fairly large quantity of neptunite. The mineral was, 

 thus, found here in situ. Though this locality lies only a 

 few steps distant from the locality No. 4 , where the neptunite 

 of type I had been found, not a trace of type II could be 

 observed at the locality No. 4, nor of type I at No. 2. Here 

 the mineral occurred almost exclusively in intimate association 

 with aegirine. The neptunite crystals were either immediately 

 implanted on the aegirine individuals or formed porous masses 

 in the larger interspaces between them. As the last filling 

 between the neptunite crystals as well as in all other cavities 

 occurred a dark-brown earthy intensely soiling substance, which 

 has been found to contain a large percentage of manganese. 

 The occurrence of neptunite proved to be confined to a 

 limited area. After this area had been worked for all that 

 could be obtained there, the digging was continued in the 

 neighbourhood to no small extent. During this work several 

 other minerals of great interest were met with, but no more 

 neptunite was found. 



