102 



contain both parts distributed in a very irregular way, with the 

 exception of a few very shining striae produced by crystals of 

 aegirine having been placed on the crystalline face of the erikite. 

 Generally the bright and dull parts cover an equally great area, 

 and sharp boundaries are almost always found between them. 

 If we examine the bright parts under the microscope by 

 reflected light we shall see that they are covered with numbers 

 of very small black parts of a quite irregular form, probably 

 representing small depressions in the face. 



To this is further to be added that the surface of the cry- 

 stals in many places is covered by quite a network of small 

 needles of aegirine imbedded in the erikite, between which 

 parts of white analcite almost always are found; also are the 

 crystals frequently interrupted by crystals of arfvedsonite. Thus 

 it is seen that the erikite always displays a very motley and 

 irregular appearance. 



The size of the crystals varies from 3 — 15™"^. The most 

 comtnon size is somewhat less than I''", and, as seen from 

 the figures, the extent is almost the same in all direclions. 



Occurrence. 



As before mentioned the erikite is found in pegmatitic 

 veins in the nepheline-syenite, especially in the lujavrite, but 

 also in sodalite-syenite, which two rocks are on this locality 

 found imbedded between each other. 



Otherwise the manner of the occurrence is somewhat 

 different. The greater part of the mineral has been found in 

 one single pegmatitic vein of rather small extent (less than 

 1*^"), but containing a considerably great number of crystals of 

 erikite. These crystals are here on all sides imbedded between 

 the other minerals. The pegmatitic vein is almost exclusively 

 formed by arfvedsonite and aegirine together with later formed 

 analcite and natrolite. The arfvedsonite is often found in 



