ORDER v. PRISMATIC IRON-MICA. 189 



Sim. Fig. 72., only having the edge of the py- 

 ramid replaced. St Austle, Cornwall. 



3. ^. (Pr 4- ) 5 . (? + oo) 6 . ?r + oo. 

 % 



Pr + oo. Cornwall. 

 Cleavage. Pr -f- oo highly perfect. Traces of 



?r + OD and iZl^ = 90 55'. Fracture 

 2 



not observable. Surface, Pr + QD smooth ; the 

 rest of the faces streaked parallel to the edges of 

 combination with Pr + GO. 



Lustre pearly, almost metallic upon Pr + CD. The 

 rest of the faces possess vitreous lustre. 



Colour pale blackish-green ... indigo-blue. It is 

 green in the direction of the axis and in the 

 plane of inclination, also perpendicular to the 

 latter, but of a pure blue colour nearly in the 

 directions of (Pr + oc) 3 , and perpendicular 

 upon Pr. The united effect of both produces 

 the common dirty indigo-blue colour. Streak 

 blueish-white, very soon changed into indigo- 

 blue. The powder produced by crushing the 

 mineral in a dry state is liver-brown. Trans- 

 parent ... translucent; least transparent in a di- 

 rection perpendicular upon Pr + oo. 



Sectile. Thin lamina? are perfectly flexible par- 

 allel to the intersection of Pr -f oo with 



? pr -7L 2 . Hardness = 1-5 ... 2-0, the 



*v 



