some of the Substances which accompany it, &c. 335 
Fibrolite . 
Silica - - ~ 3 ^ . 
Alumina - - " - 58,25 
A trace of iron, and loss - - 3>75 
100 , 00 , 
This is the only stone I have ever met with, that yielded 
nothing but silica and alumina ; for the quantity of iron was so 
small as hardly to be taken into account. I have repeated this 
analysis three times ; and have not found a difference of half a 
grain. 
Thallite in Crystals , with a rough Surface. 
Silica - - 
Alumina - - ~ - 2 b 
Lime - 1 5 
Iron - - “ - 1 1 
Loss - 1 
100. 
Thallite in Prisms like the Tourmalin. 
Silica 4 ° 
Alumina - - » 25 
Lime - 
Iron - - - - “ 13 >5 
Loss - 2 
100 , 0 , 
% 
«• 
X X 2 
