ORDEB IV. PRISMATIC BRITHYNE-SALT. 55 



Simple forms. P-co(P); ? {{} = 



_ p (M _ g()0 



1102 21'' -3- W> hoo(Jf;- 



6' ; |^(0 = 74 29' ; r + OD (*). 

 Char, of Comb. Hemi-prismatic. Inclination of 

 P oo to P r + OD = 112 49' ; to = 



<v 



14/; toP+ oo = 



p 



Combinations. 1. P GD. _. Fig. 59. 



& " . " 



2. P 00. ?. P + 00, 



p 



3. P oo. _. P -f oc. Pr + OD. 



?r + OD. Fig. 60. 



Cleavage. P oo, perfect ; traces of P -f oo, in- 

 terrupted by conchoidal fracture. Fracture 



T> 



conchoidal. Surface; P oo and still more so, 



streaked parallel to their common edges of com- 



bination. P -f oo partly uneven, but smooth and 



shining. 

 Lustre vitreous. Colour yellowish or greyish- 



vrhite. Streak white. Semi-transparent ... 



translucent. 

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



