PHYSIOGRAPHY. 



Simple forms. ! (P) = 73 45' PHILLIPS; 



Char, of Comb. Tetarto-prismatic. Inclination 



of ? upon r F+Q0 . = 93 IS' PH. 

 2 r 2 



Combination. l. r P + ^ fr+oo. Fig. 82. 



2 ^ 



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



tained, less distinct r i_?., least of all _I. 



Fracture uneven. Surface, streaked parallel to 

 the common edges of intersection, between the 

 forms. 



Lustre pearly upon ?r -f <x>, particularly if pro- 

 duced by cleavage; inclining to vitreous, or vi- 

 treous upon the rest of the faces, the former 

 particularly upon faces of cleavage parallel to 



"*" Qp > if they are easily obtained. Colour 



generally white, often passing into blue,, some- 

 times inclining to green or grey. Frequently 

 spots of berlin-blue elongated in one direction, 

 upon a paler ground. Streak white. Transpa- 

 rent ... translucent. 



Brittle. Hardness = 5-0 . . . 7-0; the lowest degrees 

 upon Pr + oo, the highest on the solid angles and 

 edges. Sp. Gr. = 3-675, a blue, transparent 

 variety, cut and polished; 3-559 a milk-white 

 variety of Rhaetizite. 



