187 



obtuse angle ß and forms with the axis à an angle varying 

 4° 5' — 10° on the average 7°; the mineral is accordingly op- 

 tically negative. There is inclined dispersion; y</); the double 

 refraction is strong and is for faces ф^ {OOlj = 0'0297, as 

 measured by Babinet's Compensator. 



Occurrence. As mentioned above the epistolite is found in 

 pegmatitic veins and in masses of grained albite. In the dif- 

 ferent localities it is found with somewhat different surroundings; 

 the greater part of the mineral from the two places North 

 of the Firth of Tunugdiiarflk appears in flat plates, almost 

 always surrounded by albite, which has evidently crystallized 

 later than the epistolite, as it follows exactly the form given 

 by it. Of the other minerals from these places sphalerite has 

 evidently also crystallized later than the epistolite and the same 

 is the case as regards the new mineral schizolite (Winther), 

 which Flink calls «pink columns». The relation to the soda- 

 lite is not so clear, it seems however as if the epistolite had 

 crystallized first. The steenstrupite presents itself in an essen- 

 tially different way in the two localities ; at Nunarsiuatiak it 

 protrudes through the plates of epistolite and is accordingly 

 older, at Tutop Agdlerkofia its form has evidently been influenzed 

 by the epistolite and therefore must it have been formed later. 

 The relation to the aegyrite is very different; this mineral had 

 partly crystallized before , partly after the epistolite and as 

 mentioned above they could also have crystallized at the same 

 time. 



When examining the pieces found in the localities at the 

 Firth of Kangerdluarsuk the age relations are more difficult to 

 trace. The epistolite is generally found here as irregular 

 masses imbedded in albite, microcline-microperthite, sodalite, 

 arfvedsonite, aegyrite, steenstrupite, eudialyte and sphalerite and 

 it seems to be a later formation than most of these minerals. 

 It is also found together with rinkite and polylithionite and is 

 often connected with these minerals in a more charateristical 



