Deseription and Analysis of the Sillimanite. 217 
Per 100 Parts. 
Al. Water, - 00.510 ceo oxygen, 
B. Silica, 43.000 21.629 
C. Alumine, 54.210 | « a 25.315 
D. Peroxide of Iron, 02.000 
99.720 
100.000 
.280 Loss. 
In order to verify the above results this analysis was va- 
ried as follows, viz. After having ascertained the loss by cal- 
cination, and separated the silex in the usual manner, the 
solution in muriatic acid wassaturated with potash, and the alu- 
mine and iron then precipitated by hydro-sulphuret of potash. 
These two substances were afterwards separated by the ac- 
tion of caustic potash. The solution to which the hydro- 
sulphuret had been added, was then tested, and was thus 
found to contain neither lime nor magnesia. Three analy- 
ses which were made of this mineral, coincide almost ex- 
actly in their results, and give, as a mean, its composition 
as follows. 
Per 100 Parts. 
Water, 00. 510 containing oxygen, 
Silica, 42.666 21.460 
Alumine, 54.111 es 6 25.270 
Oxide of Iron, 01.999 és “ 
99.286 
100.000 
. 714 Loss. 
It is therefore a silicate of alumine, with an accidental 
portion of oxide of iron, and its mineralogical formula will 
be CS. 
The mineral which this substance most strongly resembles 
in external characters, is the anthophyllite. ‘There is how- 
