Meddelelser om Grønland . Fi2 17. 131 trical relations with the plane of symmetry coinciding with thetwin-plane. The nature of the faces have partly been mentioned in thepreceding: in most of the crystals they are generally dull; afew small crystals with rather bright faces may however befound, especially among those from Naujakasik. Almost allthe faces are moreover rather uneven what is seen especiallydistinctly on è{010) which is often of considerable size; it isslightly undulating without any distinctly predominant direction,which latter fact holds good also with regard to most
Meddelelser om Grønland . Fi2 17. 131 trical relations with the plane of symmetry coinciding with thetwin-plane. The nature of the faces have partly been mentioned in thepreceding: in most of the crystals they are generally dull; afew small crystals with rather bright faces may however befound, especially among those from Naujakasik. Almost allthe faces are moreover rather uneven what is seen especiallydistinctly on è{010) which is often of considerable size; it isslightly undulating without any distinctly predominant direction,which latter fact holds good also with regard to most of theother faces. Combination-striation is only found in the zone-portion (f, r, n) = ({OOI}, {?02}, {?01}), and in one singlecase between a{lOO} and an adjacent prismatic face (/?{?10}by Winther). Physical properties. The cleavage is exceedingly strong after a{lOOJ and c(oOl)there is no perceptible difference between the two directions,and not the sligthest trace of any third direction can be surface of fracture is uneven; t
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