90 



18. Eudialyte. 



This mineral, which is so widely distributed in the Green- 

 landian sodalite-syenite, is of comparatively rare occurrence on 

 the plateau of Narsarsuk. It has been met with at only one of 

 the localities there, viz. No. 8. Here the eudialyte seems to be 

 the mineral that has been last formed, as it fills the spaces 

 between the other minerals. No idiomorphic crystal individuals 

 have been found at the place ; the mineral occurs only massive, 

 and pure pieces nearly of the size of a man's fist can be ob- 

 tained. The minerals with which the eudialyte occurs in con- 

 tact are chiefly aegirine and feldspar. 



No regular cleavage has been observable either macrosco- 

 pically or in microscopic sections. Under the microscope the 

 mineral is found to be traversed by numerous cracks, but 

 they run quite irregularly and show every mark of not belong- 

 ing to the mineral in its original state. The fracture is gene- 

 rally conchoidal, sometimes splintery. Specific gravity normal, 

 i. e. 2,91. In the closed tube the mineral gives off water, 

 which reacts faintly acid. At a red heat the loss in weight is, 

 however, only 1,19 '^/o. 



The colour of the mineral is a vivid blood-red inclining 

 on violet. This colour is considerably more intense than the 

 colour of the common eudialyte from Kangerdluarsuk, which 

 generally is brownish or verging on grey. The Narsarsuk 

 eudialyte also has a more marked vitreous lustre than the com- 

 mon eudialyte. Where the mineral borders on aegirine or other 

 minerals, i. e. in the outer parts of the eudialyte masses, and 

 also along larger cracks that traverse them, it is lustreless, 

 almost earthy and of a yellowish grey or brownish colour. 



As neither crystal faces nor regular cleavage occur, micro- 

 scopical sections orientated in fixed directions could not be 

 produced. The preparations examined, which, consequently, 

 have quite an arbitrary orientation, are clear and colourless with 



