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PHYSIOGRAPHY. 



Staurotide. 



Its difference in composition from the Spodumene, it will be seen, 

 arises from the presence of water, and the substitution of potash for, 

 lithia. 



STAUROTIDE. Prismatoidal Garnet. MOHS. 



Primary form. Right rhombic prism. M on M = 

 129 31'. 



Secondary forms. 



1. 



Primary form with the acute 

 lateral edges truncated. 



2. Fig. 417. 



M on a =137 58'. 



Cleavage, h perfect but interrupted, M in traces. 

 Fracture conchoidal, uneven. Surface P sometimes very 

 rough and corroded, hollowed out in the centre. The rest 

 of the faces generally of the same quality either rough or 

 smooth. 



Lustre vitreous, inclining to resinous. Color reddish- 

 brown, or brownish-red, very dark. Streak while. Trans- 

 lucent, frequently on the edges. 



Hardness =7-0 . . . 7-5. Sp. gr. =3-724, crystals from 

 St. Gothard ; that of columnar twin-crystals from Spain, 

 the substance of which is less homogeneous, is between 

 3-3 and 3-4. 



