PHYSIOGRAPHY. CLASS I. 



_ J 4950'. f r + 1 _o,. 



~ 



Pr-f oo(J/); Pr !(?/) 118 12'; Pr 4- oo(P)- 

 Char, of Comb. Hemi-prismatic. Inclination of 

 P GO to Pr 4- GO = 104 41'. 



Pr P - 



Combinations. 1. - .(fr-f x) 3 .Pr4- oo. 



*v /C 



2. _. _f. _. (fi-4- <x) 3 .?r4- GO. Fig. 55. 



T> &, T> JJy. I 1 



8. . _. i. !l-f . (f r 4- )) 5 . 

 222 2 



Pr 4- oo. Pr 4- cc. 



4.P-oo.?- r . ?. p r _l._! r -?. 



o Q 22 



- (Pr) 3 .?r_t_ l . - 



2 2 



?r 4- co. Pr 4- GO. Fig. 56. 

 Cleavage, f r 4- oo, highly perfect, and easily ob- 

 tained ; traces of and of Pr 4- oo. Frac- 

 2 



ture conchoidal, perfect. Surface smooth and 



even, alike in all the forms. 

 Lustre vitreous, bright. Colour white. Streak 



white. Transparency perfect. 

 Sectile. Hardness = 1-5 . . . 2-0. Sp. Gr. = 1-481. 



Taste cool, then saline and bitter, feeble. 



Compound Varieties. Twin- crystals : face of 

 composition parallel to Pr 4- GO ; axis of revolu- 

 tion perpendicular to Pr 4- GO. Rare. Several imi- 

 tative shapes. Efflorescent. Mealy crusts. 



