PHYSIOGRAPHY. 



Periklin. 



Cleavage, parallel to P and T perfect, to M only in 

 traces. 



Fracture uneven. 



Lustre pearly, sometimes vitreous upon P and T. Color 

 white, yellowish and reddish. Streak white. Semi-trans- 

 parent, to translucent on the edges. 



Brittle. Hardness =6-00. Sp. gr. =2-54 . . . 2*55. 



Compound Varieties. Twin-crystals ; axis of revolu- 

 tion perpendicular to the prismatic axis. 



Fig. 333. 



M 



Massive : composition granular. 



1. Before the blow-pipe, it melts with difficulty into a semi-transpa- 

 rent glass. 



2. Analysis. 



By GMEL.IN. 



Silica 67-94 



Alumina . . 18 93 



Soda . . . . . . . 9-99 



Potash 2-41 



Lime . 0-15 



Protoxide of iron ...... 0-48 



3. It is found at Zoblitz in Saxony, entering into the composition of at 



wenite ; also in crystals with Rutile in the Tyrol, on St. Gothard, and in 



the Saualpe of Carinthia. 



