PHYSIOGRAPHY. CLASS II. 



tween yellowish-grey and clove-brown. Streak 

 white. Translucent, sometimes only on the 

 edges. 



Brittle. Hardness = 5-0 ... 5-5. Sp. Gr. = 3-129. 

 BLODE. 



Compound Varieties. Massive : composition co- 

 lumnar, straight, sometimes divergent, and rather 

 broad ; faces of composition irregularly streaked. 

 They are often aggregated in a second composition, 

 which is angulo-granular and wedge-shaped. 



OBSERVATIONS. 



1. An analysis by JOHN states the component parts of 

 the present species to be 



Silica 56-00. 



Alumina 13-30. 



Magnesia 14-00. 



Lime 3-33. 



Oxide of Iron 6-00. 



Oxide of Manganese 3-00. 



Water 1-43. 



Alone it is not altered, and infusible before the blow-pipe. 

 It is dissolved, though with difficulty, by borax, and yields 

 a glass coloured by iron. 



2. The prismatic Schiller-spar occurs in beds of mica- 

 slate, accompanied by rhombohedral Quartz, dodecahedral 

 Garnet, several varieties of Talc-mica, of hemi-prismatie 

 Augite-spar, prismatic Feld-spar, of Cobalt- and Copper- 

 pyrites, &c. Thus it has been found at Kongsberg, and 

 the cobalt mines of Modum in Norway. With hemi-pris- 

 matic Augite-spar it has been discovered in Greenland. 



3. Although, according to the present state of our infor- 

 mation, and agreeably to the principles of Natural History, 

 the determination of the present genus seems to be unex- 

 ceptionable; yet much is still necessary for a perfect deter- 



