197 



from semitransparent to opaque, all according to the color. It 

 has an imperfect vitreous luster. A special characteristic of 

 the mineral is a very marked cleavage along two faces parallel 

 with the length of the columns. 



Fully developed crystals were not found, only single columns, 

 which were striated both lengthwise and crosswise. The examina- 

 tion of pieces cleaved off shows parallel extinction on both 

 cleavage faces. The average value of the angle between the 

 cleavage faces is 85° 32^ 



The cleavage is so perfect and the mineral so brittle, that 

 after many unsuccessful trials, all attempts to grind the trans- 

 verse sections of the columns was given up. By chance it 

 then happened, that a thin plate was knocked off, at a right 

 angle with the length of the columns; an examination of this 

 plate showed, that the extinction-direction does not bisect the 

 angle between the cleavage planes. The mineral is accordingly 



J. 



monoclinic and the length parallel with the axis Ъ. 



Taking into consideration the crystalline form of the pecto- 

 lite , the cleavage -planes were chosen for base and macro- 

 pinacoid. On the striated pieces combination-striae were found, 

 corresponding to two orthodomes and one prism. 



Fig. 3. Schizolite. 



The measured angles are: 



a:m= (lOO) 

 a :.n = (100) 

 a:h = (100) 

 с :n' = (001) 

 с :m'= (001) 



Found 

 (20T) = 28° 52' 

 (101) ==*50°30' 

 (610) =*10°49' 

 (fOl) =43° 58' 

 (201) = 65° 36' 



Calculated 

 30° 4' 



64° 24' 



