NOTES ON NORWEGIAN MINERALS 1-6. 139 





1 



2 



3 



P Ap' 



79° 15' 



80° 45' 



81° 44' 



P' Ap" 



78° 50' 



79° 55' 



76° 55' 



p" A p'" 



79° 4' 



79M7' 



79° 56' 



p'" A p 



79° 3° 



76° 27' 



77° 55' 



Although the resulting media agree better than was to be 

 expected from the single measurements and agree for all four 

 individuals, and so may be pretty reliable, yet the final medium 

 79° 8' is so slightly different from that given by Brooke and 

 Miller viz. 79° 6' that there is no reason to alter the axial ratio 

 1 : 1.4643 into 1 : 1.4602, both of which are certainly only ap- 

 proximately true. 



The crystallographic habit is that described by Haidinger*), 

 with the forms iOOli, |llli, |231| and |230i, |231j and |llli 

 usually prevailing, jOOlj seldom altogether missing. The most 

 common type is illustrated in fig. 1. 



Besides, on some of the crystals from Høgtveit, small faces of 

 a pyramide of the zone (022) occur. As no uninjured crystal 

 could be procured, that showed all foui* faces of this pyramide, 

 some single measurements were obtained, thus: 



a A HI : 30° 28' . 30° 23' . 28° li', medium : 29° 41' 

 and a A 001 : 78° 18'. 



From these angles the form may be jl31| ; the corresponding 

 calculated angles for that form would be 28° 28' resp. 77° 49', the 

 discrepancies being below the limits of the possible errors in 

 the measurements. 



The type of these crystals is shown by fig. 2. 



As already observed, jOOlj is seldom missing. On the larger 

 crystals it is remarkably oblique, up to 10 degrees, but yet it 

 presents itself as a pretty even face. (Fig, 3.) 



1) Trans. Roy. Soc. Edinburgh Vol. X, 1824, No. XIX, p. 271. 



