

Dr Turner on Lithion-Mica. 265 



11.33 per cent., of protoxide. It was proved by examina- 

 tion to be pure. 



E 

 The solution from which the iron and alumina had been 

 separated, was boiled briskly to expel carbonic acid, and ren- 

 dered decidedly alkaline by carbonate of soda. A dirty- 

 white precipitate subsided, which, when heated to redness, 

 amounted to 0.543 grains of the brown oxide of manganese, 

 equivalent to 1.489 grains, or 1.664 per cent., of the protoxide. 

 It proved, on examination, to contain neither lime nor magnesia. 



This Mica is hence composed of — 



Silica, - - - - 44.28 



Alumina, - 24.53 



Protoxide of iron, - - 11.33 



Protoxide of manganese, - - 1.66 



Fluoric acid, - - - 5.14 



Potash, - - - 9.47 



Lithia, - - - 4.09 



100.50 



According to the analysis of Klaproth, (Beytrage, vol. v. p. 69,) it is 

 composed of — 



Silica, - - - 47 



Alumina, - 20 



Oxide of iron, - 15.50 



Oxide of manganese, - 1.75 



Potash, - 14.50 



98.75 



Analysis of a Mica from Altenberg, near Zinnwald. — This 

 mica accompanies the peculiar kind of topaz called pycnite. Its 

 colour is of a dull-green ; its laminae are smaller than those 

 of the Zinnwald-mica, and possess flexibility and elasticity in 

 a lower degree. Its specific gravity, when first put into 

 water, was 3.0195 ; but after being boiled for a short time to 

 expel air from between its laminae, it was 3.0426. 



Its loss, when ignited, is hardly appreciable, not exceeding 

 one quarter per cent. The fire rendered it more brittle, and 

 increased its lustre. When heated before the blow-pipe, it 



