132 



suk are brown or black-brown, those from Naujakasik are 

 of about the same colour, but may sometimes be more yellow- 

 ish, and then they are apparently quite fresh; in these latter 

 a quite sHght pleochroism may be seen, b being more strongly 

 yellow than the other directions. 



The lustre is vitreous ; on the cleavage faces a rather 



strong pearly lustre is often seen. The mineral is at most 



semi-transparent, sometimes almost opaque; in the interior rather 



great quantities of impurities are always found, mostly con- 



^ sisting in beginning trans- 



W 



CL 



Fig. 19. Schizolite, optic scheme. 



formation along fissures, 

 often also in small par- 

 ticles of aegirine. 



With regard to the optic 

 orientation I have reached 

 another result than that 

 stated by Winther; I 

 can suppose nothing else 

 than that the two cleavage- 

 directions a(lOO} and 

 с (001} have been con- 

 founded during the exam- 

 ination. Of the crystal used by Winther for determining 

 the crystallographic elements, I have cut out a piece parallel 

 to c{00i}, and in this I have found the obtuse optical axial 

 angle; on the other material used by Winther, it has scar- 

 cely been possible in any way to distinguish between the two 

 faces. Like Winther, I have also found that the optical axial 

 plan forms a right angle with Ь {oio}, that the mineral is op- 

 tically positive, and that с is parallel to the 6-axis. On the 

 other hand I have found that the obtuse bisectrix (= a) is 

 about perpendicular on c{00l} forming an angle of ca. 14° with 

 the a-axis anteriorly. The optical form is shown on the figure 

 above showing a section perpendicular on the faces a{lOO} 



