PHYSIOGRAPHY. 



Hornblende. 



263. 



38'. r on a? = 105 11'. (dodecaedre. H.) Fig. 247. 

 (triunitaire. H.) Fig. 248. x on z = 118 28'. t on x 

 = 129 8'. (accelere. H.) 



Cleavage. M highly perfect ; less distinct parallel with 

 P, and to the diagonals of the prism.' Fracture imperfectly 

 conchoidal, uneven. Surface, sometimes streaked paral- 

 lel to the axis ; sometimes all the faces are uneven. 



Lustre vitreous, inclining to pearly upon faces of cleav- 

 age in the varieties possessing pale colors. Color, various 

 shades of green, often inclining to brown ; there is an unin- 

 terrupted series into perfectly white, and into black va- 

 rieties. Streak greyish-white . . .brown. Nearly transpa- 

 rent . . . opake. 



Brittle. Hardness =5-0 . . . 6-0. Sp. gr. =3-167, ba- 

 saltic Hornblende from Lower Stiria ; 3*127, Carinthin; 

 3-026, Actynolite from Zillerthal ; 3-006, blackish-green 

 common Hornblende ; 2-931, white Tremolite. 



Compound Varieties. Twin-crystals : face of compo- 

 sition parallel, axis of revolution perpendicular to s, of Fig. 

 245. as in Fig. 250. 



Fig. 249. Fig. 250. 



This composition is also observable in massive varieties, 

 sometimes in very thin laminae, having often some foreign 



