PHYSIOGRAPHY. 191 



Euclase Eudyalite. 



Lustre vitreous. Color mountain-green, passing into 

 >lue, and white, always pale. Streak white. Transpa- 

 ent . . . semi-transparent, generally the first. 



Very brittle and fragile. Hardness = 7-5. Sp. gr. = 

 5*098, a greenish-white crystal. 



1. Before the blow-pipe, it intumesces in a strong heat, and becomes 

 vhite. If the heat be still farther increased, it melts into a white ena- 

 nel. 



2. Analysis. 

 By BERZELIU*. 



Silica .... 43-22 



Alumina .... 30-56 



Glucina .... 21-78 



Oxide of iron .... 2-22 



Oxide of tin .... 0-70 . 



3. Nothing as yet is known with sufficient accuracy, of the mode of 

 ts occurrence in nature. The first varieties of it were brought by DOM- 

 BEY from Peru. It was afterwards found at Capao in the mining dis- 

 rict of Villa-Ricca in Brazil, where it occurs in beautifully crystallized 

 r arieties in a chloritfc slate, resting on sandstone, along with Topaz. It 

 s generally brought to Europe in fractured crystals. 



EUDYALiTE. Rhombohedral Petali n e-Spar. 

 I Primary form. Rhomboid. P on P ; = 73 40'. 

 Secondary form. 



Fig. 176. 



P on tc - 106 36' P on z - 126 



