132 
MANGANESE DEPOSITS OF KNDIA : MINERALOGY. [ PaRT T : 
8ub-Assistant S. Sethu Kama Rau in the Geological Survey labor- 
atory, with the following result : — 
Specimen No. 1061. 
CaO 24-88 
FeO 13 03 
MnO 5 84 
MgO . 2-62 
BaO 0-17 
AI2O3 0-48 
SiOj 50-96 
Combined water . . . . . I'OO 
Moisture at 100° C. 0-85 
99-92 
In this the iron and manganese have been assumed to be in the 
protoxide condition ; for the state of oxidation was not determined, 
owing to the difficulty of obtaining a sufficient quantity of the pure 
mineral. The theoretical composition of hedenbergite is as follows : — 
CaO 22-2 
FeO 29-4 
SiOa 48-4 
From this it will be seen that the Indian specimen corresponds to 
hedenbergite with a considerable proportion of the iron protoxide 
replaced by other protoxides ; these latter are the MnO, MgO, BaO, and a 
small proportion of the CaO, there being an excess of this last 
constituent over that required for the CaO group of the mineral. 
Although only one large specimen of this mineral was foimd, it is not 
improbable that the small granules of pyroxene occurring in the crystal- 
line limestone at this locality are also hedenbergite, though perhaps not 
always manganiferous. 
Brown and Yellow Pyroxenes (Sch-^fferite and Urbanite). 
In the Indian manganese-bearing crystalline rocks of Archaean age 
there are several occurrences of pyroxenes 
ccurrence. showing some tint of brown in the hand- 
specimen and shades, of yellow and pale brown under the micro- 
scope. Pyroxenes of these tints have been found in the igneous 
rocks of the kodurite series in the Vizagapatam district, Madras, where 
they especially affect the manganese-pyroxenites ; whilst in the areas 
where the gondite series occurs such pyroxenes occur both in igneous 
rocks intrusive in the gondite series (in the Bhandara and Chhindwara 
districts, Central Provinces), and in the metamorphic rocks of the gondite 
