ORDER II. PfilSMATOIDAL HAL-BARYTE. 127 



Fundamental form. Scalene four-sided pyramid. 

 P = 128 35', 89 33', 112 35'. Vol. I. Fig. 9. 

 R. G. 



a : b : c = 1 : ^1*6363 : ^0-6111. 



Simple forms. P - oo (Jc) ; P (z) ; (Pr I) 3 

 (y) = 113 14', 126 29', 90 37' ; (Pr + cc) 3 

 (d) = 78 35' ; (P -h oo) 4 (0 = 44 30'; Pr 

 (M) = 76 % ; Pr + oo (*) ; Pr (o) = 103 58' ; 

 ?r + OD (P). 



Char, of Comb. Prismatic, 



Combinations. 1. Pr. (Pr -f oo) 3 . Pr -f oo. 

 Sim. Fig. 9. Bristol. 



2. ?r. Pr. (Pr + oo) 3 . ?r + QD. Strontian 

 island, lake Erie. 



3. Pr. P. (Pr + oo) 3 . Pr + o>. Sim. Fig. 17. 

 Montecchio near Vicenza. 



4. Pr. Pr. (?r I) 3 . Pr + oo. Lengthened 

 in the direction of the edges between Pr and 

 ?r H- oo. Ghibesa, Sicily. 



5. Pr. Pr. P. (?r + oo) 3 . Pr -f- QD. Sim. 

 Fig. 21. Lengthened in the same direction. 

 Bex, Switzerland. 



6. Pr. (Pr I) 3 . Pr. P. (Pr + <x) 3 . 

 (? -f- x) 4 . Pr -j- CD. Monte Viale near 

 Verona. 



Cleavage. Pr + CD, highly perfect ; Pr less easily 

 obtained, and often interrupted by conchoidal 

 fracture ; P as is still less distinct, and only 

 faint traces are observable parallel to Pr -f- CD. 

 Fracture imperfect conchoidal, uneven. Surface, 

 P x generally rough ; Pr sometimes streaked 



