558 



WATSON AND WHERRY: PYROLUSITE FROM VIRGINIA 



The axial ratio derived from the measurements is clearly dif- 

 ferent from that usually accepted for manganite, but agrees almost 

 exactly with that obtained by Flink on crystals from the Bolets 

 Mine, Undenas district, Sweden, a:b: c = 0.8612:1:0.5629.12 

 From three closely agreeing measurements of the unit prism, its 

 = 49° 15' ± 5' whence a = 0.8616 ± 0.0025; and from two of 



:^/9 



Fig. 1. 



dome 032 its p = 40° 10' ± 5', whence c = 0.5628 ± 0.0020. 

 As Flink's crystals were probably better than the present ones, 

 his values are used in calculating the angle-table. The differ- 

 ence between this axial ratio and that usually accepted for man- 

 ganite, 0.8441 : 1 : 0.5448, is perhaps connected with the loss of 

 hydrogen, corresponding to the change into pyrolusite, taking 



12 Arkiv Kemi Min. Geol. 3: (35), 101. 

 erties of the mineral are given. 



1910. No analyses or physical prop- 



