78 
MANGANESE DEPOSITS OF IXDIA : MINERALOGY. [PaRT I : 
it is light steel-grey, with, a dead-black streak. It is slightly mag- 
netic, has a hardness of 6'5 and specific gravity of 4"80, determined 
on a piece weighing 34 grammes. This piece was powdered and the 
analysis kindly undertaken by Mr. Fawcitt. The result was as foUows : — 
MnO« 
MnO 
Fe203 
A1203 
CaO 
MgO 
P2O5 
CO2 
Si02 
Combined water (by difference) 
100 00 
The unusually large amount of manganese peroxide shows that the 
mineral is different from the other manganese-ores found in India ; of these 
the only mineral that contains such a high percentage of Mn02 is pyro- 
lusite, which is much too soft for the present mineral. Considering this 
fact there seems no alternative to regarding the mineral as pohanite 
rendered impure by the presence of some 7-1 per cent, of foreign material, 
present either as another mineral mechanically mixed with the pohanite, 
or as impurities mechanically included in it. If the former be the case 
then it is probable that the other mineral is braunite, in which the silica 
would be contained. [A careful examination of the specimen with a lens 
seems to show that it is made up of two constituents of which one 
might be braunite and the other hoUandite, the latter being present in 
by far the larger amount. But the analysis renders it improbable that 
this is the composition of the ore and consequently it is necessary to 
suppose that the mineral that suggests hoUandite is really pohanite. 
I shall not, however, be satisfied with this determination until I have 
obtained some definitely crystaUized specimens of the mineral showing 
the crystalhne form of pohanite.] 
Pyrolusite. 
Pyrolusite is the peroxide of manganese, Mn02, containing, when 
theoretically pure, G3'22 per cent, of manganese. It crystalhzes in the 
Cha acters orthorhombic system in forms that are supposed 
to be the result of the formation of this mineral 
from manganite by dehydration ; the manganite (Mn203.H20) giving 
up its water, with the production of pyrolusite (Mn02) often containing 
a certain proportion of residual water. At the same time the manganite 
92-55 
2-69 
160 
070 
061 
0 25 
0 07 
trace 
0 80 
073 
