396 
MANGANESE DEPOSITS OF INDIA : GEOLOGY. 
[Part II : 
This layer is usually about half an inch thick, but in places as much as 
one inch thick. It has an iron-black polished surface, with in places a 
sort of mammillated appearance. In some places there are thin layers 
of radiated pyrolusite in the psilomelane, and the underlying limestone 
contains quite a quantity of secondary pyrolusite, which is most 
abundant near the coating of psilomelane. This occurrence probably 
illustrates the following points : — 
1. The waters of the Pench river contain salts of manganese in 
solution. 
2. The dissolved manganese is most easily deposited as oxide where 
the water containing it comes in rapid contact with the 
air, namely at the waterfall. 
3. This manganese oxide is deposited on the manganiferous lime- 
stones in preference to the non-manganiferous ones. 
This psilomelane was undoubtedly deposited comparatively recently ; 
for it follows all the carvings of the limestone and was therefore deposit- 
ed after the river carved the limestone to its present shape. It 
seemed, however, as if the psilomelane was actually being denuded 
away by the river at the time of my visit ; not, of course, by solution, 
but by the wearing action of the waters. 
In a pond near Rambha in Ganjam, I found in January 1905 that the 
Manganese deposited in a water on evaporating had left a deposit of 
pond near Rambha. manganese oxide on the gravelly sides of the 
pond, each piece of stone being so coated. 
Another interesting example is a deposit of pyrolusite found on the 
surface of Bijawar limestone in a nala at a point about three-quarters of 
a mile S. S. W. of the camping place in the 
i yi oiusite at an uan. D^^r forest known as Pan Kuan. In one place 
the limestone surface had been corroded and coated with a deposit of frag- 
ments of pyrolusite cemented by calcareous tufa. Close by was a 
steeply sloping surface of limestone with a coating of almost pure pyro- 
lusite, containing in places patches of dark brown crystalline calcite, and 
showing at the junction with the limestone a gradual passage into it, 
indicating that the pyrolusite was formed by the replacement of the 
limestone. When I saw this occurrence the nala was quite dry ; but 
in the rainy season it must often carry a large quantity of water. This 
must have taken into solution a portion of the manganese that is so 
widely distributed in the Lameta rocks of this area ; and coming in 
