476 DR T. THOMSON'S Analysis of some Minerals. 



tinge ; this may probably depend upon the proportion of iron 

 which they respectively contain. 



Texture foliated. Sometimes it is crystallized. I possess a 

 crystal 4 inches long, 1.3 inch broad, and 0.9 inch thick. It 

 constitutes a four-sided prism, which appears perfectly rectangu- 

 lar, by the most careful measurement. But the crystal has no 

 regular summit, nor will it cleave in the direction perpendicular 

 to the axis. We have no means of knowing, therefore, whether 

 the prism be right or oblique. 



Lustre waxy, dull, except when particles of foreign matter 

 are mixed with it. 



Opaque, or only slightly translucent on the edges. 



Hardness 3.5 to 6. 



Streak yellowish-white. 



Specific gravity 2.598, as determined in my laboratory. Dr 

 BARKER states it to be 2.698. 



Before the blowpipe becomes white and friable, and gra- 

 dually fuses into a white opaque bead, but not nearly so readily 

 as spodumene. With carbonate of soda it fuses into a transpa- 

 rent glass ; with borax or biphosphate of soda, into a colourless 

 glass, leaving a silica skeleton. 



It was twice analyzed in my laboratory, first by Captain 

 LEHUNT, and then by Mr WILLIAM BLYTHE. The constituents 

 were as follows, 



Silica, ........ 49.08 47.925 



Alumina, 30.60 31.041 



Potash, 6.72 6.063 



Protoxide of iron, ..... 2.27 2.328 



Lime, 0.68 0.724 



Magnesia with some manganese, 1.08 0.459 



Protoxide of manganese, . . 1 .255 



Water, ........ 10.00 16.000 



100.43 99.795 



