OF ARTS AND SCIENCES. 97 



Crystalline Form op Antimontous Iopipe. 



MoNOCLiNic Variety. 



Forms {001}, {110}, {210}, {Oil}, {211} 



Fig. 6, Plate I. 



Fundamental Angles. 

 Between normals of 210 and 2T0 measured 75^ 21' 



Angle of Axes TO'' 16' 



Clinodiagonal, a = 1.6408 

 Orthodiagonal, 5 = 1. 

 Vertical, c = 0.6682 



Angle between basal edges made by {001} and {210} 100° 16' 

 55 . „ ,5 55 „ {001} „ {110} 62° 44' 



Basal edge angle at end ) ^^^^ ^g, corresponds to the ) ^^^^ ^g, 

 of clinodiagonal ) prismatic angle j 



Do. 62° 44' do. 65° 51' 



Vertical axis on the assumption that the forms {001} 



and {211} are orthorhombic 0.867 



The crystals have a very well defined cleavage, parallel to the basal 

 plane. 



We endeavored to supplement the above crystallographic measure- 

 ments by a study of the optical characters of the crystals ; but, unfor- 



VOL. XIII. (n. S. V.) 7 



