370 DR T. THOMSON on Asbestus, Chlorite, and Talc. 



II. CHLORITE. 



THE name Chlorite was first introduced into mineralogy by 

 WERNER, and applied by him to a mineral, which preceding 

 mineralogists had confounded with mica, and which HAUY after- 

 wards considered as a variety of talc. 



I employed, as a specimen of chlorite for analysis, a very 

 pure piece of common chlorite from the Isle of Bute. 



Its colour was very dark green. It was composed of very 

 small scales, attached to each other without any visible cement- 

 These scales were so small, that I could not distinguish their 

 shape by means of a common magnifying-glass. Streak light- 

 green. 



Opaque. Soft enough to be scratched by the nail. 



Lustre silky, approaching to resinous. 



Sectile. Easily frangible. 



Specific gravity 2.823. 



Its constituents were found to be as follows : 



Silica, 27.624 



Protoxide of iron, . . 27.544 



Alumina, ; ''."I % . . 23.708 



Magnesia, '. ."' . . 10.960 



Water, 9.160 



98.996 

 This is equivalent to 



16 atoms silica, 



7 atoms protoxide of iron, 

 12 atoms alumina, 



5 atoms magnesia, 



9 atoms water. 



