Chap. XXXVIII. 1 sandur state. 
1011 
figure 78. At Ritmandrug Main Bed, as already noticed on page 1007, 
a tunnel driven into the working face has shown that the manganese- 
ore does not continue down on its dip for any depth, but gives way 
to these lithomargic rocks. 
On page lOlG, in noticing the manganese minerals found in these 
deposits, I have described how the psilomelane 
Siimnuny of origin. ,11 i i ■ i 1 1 i 
and wad have been derived by replacement 
from phyllitic rocks. What I think all the foregoing evidence, taken in 
conjunction with this, points to is that where these manganese-ore de- 
posits now are there were originally phyllites, containing both magnetite 
and a small quantity of manganese. Waters then percolated through the 
masses of rock and took the manganese and iron into solution, leaving 
the leached rock behind in the form of a lithomargic mass of variegated 
colour. The solutions containing manganese and iron may not have 
deposited their burden exactly in the same place as where they obtained 
it. They had the whole length of the Sandur Hills in which to operate. 
WTiere, however, conditions were favourable the manganese and iron in 
solution, doubtless as carbonates, were oxidized and deposited, though 
not usually in the same places. Once a certain quantity of one element 
had been deposited, segregative tendencies would probably come into 
play and cause the selective deposition of further quantities of the same 
substance at the same place — the other constituent being carried 
further on and deposited elsewhere, in some cases close by, and in 
others at a considerable distance. Wherever the deposition took place, 
solution of the phyllitic rock, in some cases fresh and previously 
unaltered, and in other cases already altered during the leaching out of 
its iron and manganese, had to take place to make room for the 
substance being deposited. Thus it is that the deposits seem to have 
been formed by metasomatic replacement. From the fact that the 
manganese-ores so often contain magnetite, it looks either as if the 
magnetite were less soluble than the manganese in the phyllite, or as if 
in a very large number of cases the rock replaced by the manganese-ore 
were fairly fresh. As regards the disposition of the material taken into 
solution when the manganese was deposited, the same difficulty arises as 
in the Central Provinces In some cases, perhaps, the masses of 
lithomarge associated with the manganese-ore deposits represent the 
aluminous material taken into solution. But, considering the banding 
Z D 
