137 



Systematic. 



By a comparison between the crystallographic elements of 

 schizolite, pectolite, and wollastonite , it will be found that 

 these three minerals are as very nearly isomorphous; for schi- 

 zolite are : 



a:b:c = 1-10613 : 1 : 0*98629 



a = 90° 1Г, /9 = 94° 45^/4', y = 103° 7V4'. 



a :c = (100) :(00l) = 94° 56' 



while in pectolite and wollastonite (after E. S. Dana, Mine- 

 ralogy 1892, p. 373) they are respectively: 



a:b:c = MHO : 1 : 0-9864 ß = 95° 30' 

 a:b:c = 1-05312 : 1 : 0-96761 ß = 95° 30' 



The physical qualities are essentially alike for all the 

 minerals, especially the cleavage after a{l00} and c(00l}; 

 while the wollastonite in its optical relations is more deviating, 

 it is a feature common to schizolite and pectolite that the acute 

 bisectrix is parallel to the è-axis; the size of the optical axial 

 angle is also about equal in both minerals, and they are both 

 optically positive ; on the other hand they are deviating in the 

 fact that the obtuse bisectrix in the pectolite is about perpen- 

 dicular on a {100) while in schizolite, according to what is 

 stated above, it is about perpendicular on c{00l}. If we inter- 

 change the a- and c-axis in the shizolite we shall get optical 

 congruity between the two minerals ; but at the same time the 

 isomorphism of the crystallographic features disappear, so that 

 there can scarcely be any doubt that the position chosen is 

 the one that expresses in the best way the resemblance with 

 pectolite. 



Now the schizolite, as mentioned in the introduction, is 

 also to some degree related to the rhodonite (and to the 

 babingtonite which is in all respects related to the latter). 

 Both minerals are manganese-silicates, triclinic, and with strong 

 cleavage in two directions. The rhodonite, however, is with 



