26 



PHYSIOGRAPHY. 



Anorthite Anthophyllite. 



Secondary form. 



MonZ 

 T on I 

 P on e 

 P on n 

 P on t 



Fig. 30. 



117 25' 

 120 30 



137 32 

 133 13 



138 46 



Cleavage, parallel to P and M ; none parallel to T. 



Fracture conchoidal. 



Surface of T more smooth than of I. 



Lustre pearly upon cleavage planes, vitreous in other di- 

 rections. Color white. Streak white. Transparent . . . 

 translucent. 



Brittle. Hardness = 6-0. Sp. gr. = 2-763 (massive) ; 

 = 2' 656 (small crystals, apparently not entirely free from 

 Augite.) 



1. Before the blow-pipe it behaves like Feldspar, except that with so- 

 da it does not give a clear glass. It is entirely decomposed by concen- 

 trated muriatic acid. 



2. Analysis. 



By ROSE. 



Silica .... 44-49 



Alumina .... 34-46 



Oxide of iron . . . . 0-74 



Lime .... 15-68 



Magnesia .... 5-26 



3. The only locality of Anorthite is Mount Vesuvius. It is found lin- 

 ing cavities in Limestone, along with a green variety of Augite. 



ANTHOPHYLLITE. Prismatic Schiller-Spar. 

 MOHS. 



