ODDER VI. HEMI-PRISMATIC AUGITE-SPAR. 277 



Brittle. Hardness = 5-0 ... 6-0. Sp. Gr. = 3-167 

 basaltic Hornblende from Lower Stiria; 3-127 

 Carinthine ; 3-026, Actinolite from Zillerthal ; 

 3-006, blackish-green common Hornblende; 2-931 

 white Tremolite. 



Compound Varieties. Twin-crystals : face of 

 composition parallel, axis of revolution perpendicu- 

 lar to ?r + QD. This composition is also observ- 

 able in massive varieties, sometimes in very thin la- 

 minae, having often some foreign substance, parti- 

 cularly laminae of the preceding species, interposed 

 between them. There is also composition parallel to 



. Massive : composition granular, individuals 



of various sizes, generally strongly cohering, and 

 producing in the great a tendency to slaty fracture ; 

 composition columnar, individuals of various sizes, 

 sometimes very delicate, generally long, parallel, or 

 diverging, and aggregated in a second granular 

 composition. Compositions of short and irregular- 

 ly distributed columnar particles possess in the 

 great a slaty fracture. Very thin columnar composi- 

 tion produces a silky lustre. 



OBSERVATIONS. 



1. Hornblende, Actinolite, and Tremolite, together with 



direction of Pr + co. The varieties which present it are faint- 

 ly translucent, and shew a pale brown colour in thin splinters, 

 but appear dark grey in the mass. They were discovered at 

 Kassigiengoit in Greenland by Sir CHARLES GIESECKE, and 

 formerly considered as Hypersthene. Mr BROOKE first recog- 

 nised them to belong to the present species. H- 



