Chap. IIT. ] 
BRAUNITE. 
6^ 
For the purpose of calculating from these figures it is found to be 
necessary to assume that the ferric oxide replaces an equivalent quan- 
tity of manganese sesquioxide, Mn203, and that the oxides of barium, 
calcium, and magnesium, replace equivalent amounts of manganese 
protoxide, MnO. Neglecting, then, all the constituents of the analyses, 
except the Mn02, MnO, Fe203, BaO, CaO, MgO, and Si02, and replacing 
the oxides of iron, barium, calcium, and magnesium, by equivalent 
amounts of manganese oxides, and splitting up the Mn203 so obtained 
from the Fe203 into MnO and Mn02, the composition of the three 
specimens works out as follows : — 
Gaiividi. 
Kacharwahi. 
Ki> jlidongri. 
IVInO .... 
45-22 
46-64 
51-21 
Mn02 .... 
44-75 
43-22 
41-72 
Si02 .... 
8-25 
8-60 
10-26 
98-22 
98-46 
103-10 
Manganese 
63-32 
63-43 
66 05 
Available oxygen . 
8-23 
7-95 
7-67 
Reduced to 100, these 
correspond to : 
Garividi. 
Kacharwahi. 
Kajlidongri. 
MnO .... 
46-04 
47-37 

49-64 
Mn02 .... 
45 -56 
43-90 
40-42 
Si02 .... 
8-40 
8-73 
9-94 
100-00 
100-00 
100-00 
Manganese 
64-47 
64-43 
64-00 
Available oxygen . 
8-38 
8-07 
7-43 
The formula for braunite usually given in text-books of mineralogy 
is that of Rose and Rammelsberg (see page 65) ; but this corres- 
ponds to 9*98 per cent, of sihca. Although some of the published 
analyses show this amount, many of them show a considerably smaller 
quantity of Si02. This probably means that the relation of Mn203 to 
MnSiOs is not always 3:1, but is sometimes greater than this value. 
