64 



the zone of the «-axis are often less distinct or only indicated 

 by striation. Also the faces of the second and third pinacoids, 

 Ъ and c, are generally very narrow on crystals of this type. 



Besides the forms mentioned above I have found on the 

 new material two new ones, viz. 



к = {301] and = {312}. 



The form к symmetrically truncates the combination-edge 

 (313) : (ЗТЗ) (Fig. 6, Plate III), by which its symbol is fully 

 determined. The form о is in the zone between p and e. There- 

 fore, the ratio of the a- and ô-axes is the same for it as for 

 p^ i.e. a : ЪЪ. The following values of angles may also be 

 given. 



Measured Calculated 

 : С = (312) : (OOl) = 46° 51' 46° Ы 

 к : с = (301) : (OOl) = 61° 56' 61° 40' 



These two forms complete an important zone, whose symbol 

 is [133] and to which the following faces belong: 

 (on), (312), (301) and (31о). 



The epididymite crystals belonging here are generally at- 

 tached by one end either singly or in irregular groups. Some- 

 times several individuals present a regular orientation, being 

 grown together by the ô-pinacoids and having their basal faces 

 in a common plane, by which tolerably wide plates have 

 been formed. 



Tw in s are not uncommon, and are formed by two individuals 

 with common c-axis crossing each other at an angle of 60° ; 

 when a third individual is present, a regular star of six rays is 

 formed (a trilling). The plates mentioned above often consist 

 of such twinformations , a system of parallel needles being 

 traversed at an angle of 60° by another (often also by a third) 

 such system. Only penetration twins have been observed. 



As mentioned above, the epididymite of type I is of most 

 common occurrence on Narsarsuk. It has been observed at the 



