138 



regard to crystallographic and optical qualities rather widely 

 distant from the other minerals in the group, and approaches 

 more nearly to pyroxene as it appears in the crystallographic 

 elements from the arrangement for the rhodonite proposed by 

 Fl ink ^) according to which 



a:b:c = Г0729 : 1 : 0-6213 



a = 103° 18', ß = 108° 44', ;- = 81° 39'. 



a:c = (100): (001) = 107° 23V2' 



while in pyroxene they are 



a:b:c= I -0921 : 1 : 0-5893 

 ß = 105° 50' 



By this arrangement it is further obtained that the two 

 cleavage directions get a uniform position (as prismatic faces) 

 in both minerals, and with about the same angle, which in the 

 rhodonite is 



m:M = (llO):(lTO) = 92° 28V2' 

 and in pyroxene 



m -.m = (110):(lT0) = 92° 50' 



In the schizolite the angle between the two cleavage direc- 

 tions is 85° 4' (94° 56'), accordingly essentially different from 

 the above. If we try to arrange the mineral in a way analog- 

 ous with the rhodonite it will be seen that also in other direc- 

 tions they agree very badly. The transformation must take 

 place in such a way as to make c{00l} to (l I o}, a(lOO} to 

 {no}, è[oTo} to {001}, y{\Q\] to {100}, and ш{ГТо} to 

 {111} a. s. 0., so that the new indices {//, Ä:, /,} are derived from 

 the old ones {hkl\ according to the form : 



/г, = / — h 

 l. = —к 



') Zeitschr. f. Krystal, ti, 1886, p. 506. 



