ORDER VI. HEMI-PJIISMATIC KOUPHONE-SI'Ali. 



more or less uneven ; M often concave, s and s? 

 convex. 



Lustre vitreous. The faces M possess high de- 

 grees of pearly lustre, both as faces of cleavage 

 and of crystallisation. Colour, various shades 

 of white, prevalent, passing into red, grey, and 

 brown. Streak white. Transparent ... translu- 

 cent on the edges. 



Brittle. Hardness = 3-5...4-0. Sp. Gr, = 2-200, 

 white crystals from Iceland. 



Compound Varieties. Massive : composition 

 granular, the individuals being of various sizes, 

 sometimes easily separable, sometimes strongly co- 

 hering ; faces of composition in most cases uneven 

 and rough. Globules formed in vesicular cavities. 



OBSERVATIONS. 



1. Of several of the older analyses of Stilbite, it i im- 

 possible to say whether they refer to this or to the preced- 

 ing species. LAUGIER obtained from 1., a red variety from 

 the Tyrol, and WALMSTEDT from 2., a variety called 

 Heulandite, the following results : 



Alumina 1. 10-00. 2. 7*19. 



Silica 45-00. 59-90. 



Carbonate of Lime 16-00. 0-00. 



Lime 11-00. 1G-87. 



Water 12-00. 13-43. 



Oxide of Iron 4-00. 0-00. 



Oxide of Manganese 0-50. 0-00. 



Before the blowpipe this and the preceding species give 

 nearly the same results. 



2. What has been said in general of the natural reposi- 

 tories of the prismatoidal Kouphone-spar, refers also to the 

 hemi-prismatic one ; they occur both in Iceland and the 



