HOPEITE. 100 



HOPEITE. 

 HALOIDE. 



Hopeite. BREWSTER. Trans. Hoy. Soc. Edinb. VoL X. 

 p. 107. 



Prismatic. P = 139 41', 107 V, 86 49\ Vol. 

 I. Fig. 9. AP. 



a : b : c = 1 : *J 4-443 : V l ' 493 - 



Simple forms. P oo (g) ; P (P); (fr -f o) 5 

 (s) = 81 34' ; Pr (M) = 101 24'; Pr -f QO (0 ; 



Char, of Comb. Prismatic. 



Combination. P OD. Pr. P. (r -f x) 5 . 

 Pr -f oo. Pr + oo. Fig. 29. 



Cleavage, Pr -f oo perfect, less distinct Pr -J- QD. 

 Surface, ?r + QD deeply streaked in a longitudi- 

 nal direction, the rest of the faces smooth. 



Lustre vitreous, pearly upon Pr + QD. Colour 

 greyish-white. Streak white. Transparent ... 

 translucent. Refraction double ; two axes, the 

 principal one perpendicular to the axis of P and 

 to the face I ; angle of the resultant axes about 

 48, in the plane of P oo (g), contiguous to 

 the obtuse lateral^ solid angle of P. Index of 

 ordinary refraction nearly 1-601. 



Sectile. Hardness = 2-5 ... 3-0. Sp. Gr. = 2-76, 

 BREWSTER, of a perfect crystal 



Hopeite had been formerly considered as a variety of 

 Stilbite. According to NORDENSKIOLD, it gives off its 

 water before the blowpipe, and then melts easily into a clear 

 colourless globule, which tinges the flame green. It gives 

 no skeleton of silica with salt of phosphorus, with which it 



