CllAP. XXXIV.] C:IIII1JSD\VARA : KACIll DHANA. 
V77 
corresponded to 7Mii2();{. 2MiiSi03. On this assumption the composition 
of the ore works out as follows ;- • 
Hiiuiiiito : — 
JIn203 
FC2O3 
MiiO 
MgO 
C«0 
Si02 
Apnlilc 
Oilcito . 
AI2O3 . 
MgO (surplu,-:) 
A.S2O5 
H2O (combined) 
Moisture at 100°C 
Surplus oxygen 
73-54 
G-70 
4-33 
2- 33 
1-20 
8-75 
97-05 
97 
():. 
0 
07 
0 
13 
0 
2G 
0 
62 
0 
002 
0 
91 
0 
09 
99 
132 
0 
44 
99 
572 
The closeness of this analysis to braunite of the formula 7Mn203. 
2MnSi03 is perhaps best seen if the ferric oxide be converted into Mn203, 
and the protoxides MgO and CaO into MnO and the whole then calculat- 
ed to 100. The result is as follows :— 
Mi:0 45-15 
Mn02 46-17 
Si02 8-68 
100-00 
Manganese ......... 64-17 
Available oxygen ........ 8-48 
Tf now these figures be compared with the figures for the different varieties 
of braunite given on page 70, it will be seen that there is a very close 
correspondence with the bramiite of the formula 7Mn203.2MnSi03. 
The silica is of course the chief criterion in deciding which formula the 
braunite agrees with, but there is also a close agreement in the aroount 
of manganese. The divergences in the amounts of the tvro oxides of 
manganese are evidently due to the fact that there is a slight excess oi 
available oxygen over that required by the formula. This is within 
the limits of error in the determination of oxygen, and the difference 
may be due either to such an error, or it may indicate that there is a 
very small amount of interstitial psilomelane. The specific gravity 
of the ore is 4 '71. This is only just outside the limits for this mineral, 
