PHYSIOGRAPHY. 247 



Trona Troostite. 



in France, but is associated with pulverulent Diallogite. In small 

 quantity, also, at Sterling, (Mass ) along with Spodumene. 



TRONA. Te tart o-prismatic Natron-Salt. 



Primary form. Doubly oblique prism. MonT=103 

 15'. 



Secondary form. 



Fig. 451. 



Tonn - - - 103 15' 



n on n - 132 30 



Cleavage, perfect parallel to M. Fracture uneven. 

 Surface, M and n smooth, T streaked. 



Lustre vitreous. Color white, sometimes passing to yel- 

 lowish-grey. Streak white. Transparent . . . translucent. 

 Rather brittle. Hardness = 2*5 ... 3-0. Sp. gr. = 

 2-11. Taste, sharply alcaline. 



1. It does net deliquesce in the air. 



2. Analysis. 



Carbonic acid - 40 24 



Soda - 37-93 



Water - 21-83 



3. It is found at Fezzan in Tripoli, where it occurs mingled with the 

 soil and dissolved in water, 



TROOSTITE. Rhombohedral Parachrose- 



Bary te. 

 Primary form. Rhomboid. P on P =115 (c. g.) 



