ORDER I. PRISMATIC GY1'SUM-I1 ALO1DE. 



a:b:c = l : Jl^G-l? : % / 1-2353. 



Simple forms. P oo (P) ; P () ; (Pr) 3 (n) ; 



(P) 3 (/); P+oo(r) = 10GIO'; Pr.-f oo (T); 



Pr -f- co (I/). 

 Char, of Comb. Prismatic. 



Combinations. 1. P cc. Pr -f oo. Pr -j- oo. Aus- 

 see, Stiria. 



2. P oo. P + oo. Pr + oo. Pr 4- oo. Hall, 

 Tyrol. HAUV. 



3. P oo. P.(Pr)*. (P)*. Pr+Qo. Pr + oo. 

 Fig. 26. Aussee, Stiria. 



Cleavage. Pr 4- GO and Pr + oo highly perfect; 

 P x less distinct, yet easily obtained. Fis- 

 sures in the interior partly iridescent parallel to 

 Pr = 106 3'. Fracture imperfect conchoidal, 

 uneven. Surface, Pr -f x and Pr -f- oo smooth ; 

 P x rough. 



Lustre vitreous, inclining a little to pearly upon 

 the most distinct faces of cleavage. Colour 

 generally white ; commonly it inclines to flesh- 

 red, violet- and smalt-blue or ash-grey. Streak 

 greyish-white. Transparent, not perfectly, pass- 

 ing into translucent. 



Brittle. Hardness = 3-0. . .3-5. Sp. Gr. = 2-899 

 a greyish-white cleavable variety from Hall in 

 the Tyrol. 



Compound Varieties. Contorted : composition 

 columnar in thin fibres, parallel, and variously 

 bent. Massive : composition granular, of differ- 

 ent sizes, sometimes impalpable, and then the frac- 



