182 



PHYSIOGRAPHY, 



Epidote. 



Fig. 169. 



Cleavage, perfect parallel to M ; less so parallel to T. 

 Fracture, uneven. Surface, the lateral planes sometimes 

 streaked vertically : in general, the faces are smooth. 



Lustre vitreous, inclining to pearly upon perfect faces of 

 cleavage, and the corresponding faces of crystallization. 

 Color, green and grey, prevalent. Among the most com- 

 mon shades of the first, is pistachio-green ; in general, the 

 green lints are more inclined to yellow than in Pyroxene 

 and Hornhlende. The grey colors pass into white and a 

 very pale flesh-red. Streak greyish-white. Semi-trans- 

 parent . . . translucent on the edges. Viewed in a direction 

 parallel to the axis, the color of the crystals contains less 

 yellow than in the directions perpendicular to it. 



Brittle. Hardness =6-0 ... 7-0. Sp. gr. =3-269, va- 

 riety Zoisite, from the Saualpe; =3-425, Pistazite, from 

 Arendal. 



Compound Varieties. Twin-crystals : axis of revolu- 

 tion parallel to the prismatic axis, as represented in the an- 

 nexed figure ; angle of revolution = 180, 



