244 
MANGANESK DEPOSITS OF INDIA .* GEOLOGY. [ PaET II : 
Should anyone object to this term as implying that calcite is always 
present in these rocks, which it is not, the term^ime-gneisses could be 
used ; it is to be noted, however, that the term calcareous refers to the 
presence of lime and not of calcium carbonate. 
Rocks of the charnockite series^are not met with until the outer edge 
of the Eastern Ghats is reached, as at Taduru. 
All the manganese-ore deposits now being worked are situated in the 
coastal plain country, and, as has been already 
The kodurite series. i • i i i i it -, ■ ^ 
explained elsewhere', are regarded as derived 
by chemical alteration from rocks of which the chief constituents are 
apatite, a manganese-garnet (spandite), manganese-pyroxenes (at least 
two species), potash-felspar, and quartz. This series is evidently 
quite different from the other series of rocks in this district, and in fact 
I am not aware that rocks of a similar character have been previously 
described. Hence, I propose to call this series the kodurite series after 
the Kodur mines where its constituent rocks are weU exposed^. 
From the foregoing it will be seen that the rocks of this area, including 
„ , ^. , ^, the outer fringe of the Eastern Ghats, where also 
Relations of the o ' 
kodurite series to the some occurrences of manganese-silicate-rocks have 
other crystallines. been - detected, can be separated into the fol- 
lowing petrological groups : — 
1. Kodurite series. ' 
2. Charnockite series. ^ Igneous. 
3. Gneissose granite. J 
4. Cale-eneisses. , n/r 4, i. • 
n ^2■^. J l i • ' Metamorphic. 
5. Jvhondalite series. * ^ 
6. Contact products of 2 and 53. 
The relative ages of these rock groups are difficult to determine ; 
for they seem to be regularly interbedded one with the other, and clear 
sections showing the contacts of rocks of the different groups are 
rare. Dr. Walker, however, supposes the khondahte series, including 
groups 4 and 5 above, to be older than groups 2 and 3 ; for it was 
possibly the intrusion of these latter rocks that led to the metamorphism 
of ancient sediments into the rocks of groups 4 and 5. 
The outcrops of the various rocks at the surface take the form of 
parallel bands, and, as far as has been revealed by mining operations, the 
» Rec. G. S. I., XXXIII, pp. 96, 97, (1906); Trans. Min. Geol. Inst. Ind., 1, 
pp. 87, 88, (1906). 
2 This name has already been announced in Rec. G. 8. I., XXXV, p. 22, (1907). 
8 T. L. Walker. Ree. 0. 8. I., XXXVI, p. 1, (1907). 
