NOTES ON NORWEGIAN MINERALS 1-6. 14J 



A third locality was Aas feldspar quarry on the western 

 side of the river Otra; at this place only a few crystals were 

 gathered. 



The occurence at Landsværk is quite analogous to that de- 

 scribed by Prof. Nordenskiöld from Garta, Arendal, it being 

 disseminated in a brownish or reddish orthoclase with alteration 

 products of various kinds, among which uranochre on fine cracks. 

 The crystals are small, only 10—12 millimeters across, and 

 bounded by the faces of jiOOi only. Besides single individuals 

 decidedly in majority, there also occur twins according to the 

 spinel law with the habit of the common penetration twins of 

 fluorite. 



The mineral is apparently very much altered; its specific 

 gravity is sensibly less than that of the fresh mineral and 

 together with this black more or less altered uraninite, occurs 

 the alteration product described by Prof. Nordenskiöld by the 

 name of yttrogummite, partly as separate masses, partly as 

 yellow or reddish rims about a nucleus of less altered uraninite. 



The occurrence at Aaseland was in a reddish microline 

 perthite with oligoclase and quartz and great masses of titanite 

 filling the interstices between great biotite flakes in the fan ar- 

 rangement so very common in these pegmatite veins. 



The mineral is much less altered than that from Lands- 

 værk, with a high specific gravity and a bluish black metallic 

 lustre, uranochre occurring as thin coatings, only, on crystals 

 or in fine cracks in feldspar or quarlz. Yttrogummite has not 

 been found. 



The crystal lographic habit is hexaëdric with very subordinate 

 faces of jlllj. Among a good many specimens only one pair 

 of twins was found, jlOOj in penetration with the corners cut 

 by Slll|. 



About half a cubic meter of rock containing the fan arran- 

 ged mica was worked out, which yielded some 6 kilos of urani- 



