f*12 MANGANESE DEPOSITS OF INDIA: DESCRIPTIVE. [ pART TV : 
The following section l recorded by Mr. Bose is a typical one : — 
2' Soil. 
2' 8 ' Abundant nodules of pyrolusite, ^ inch to 6 inches in diameter, mixed 
up, as usual, with nodules of iron-ore. A little psilomelane and imd 
occurs in association with the pyrolmite. 
4' 10'' Fragments of decomposed yellowish, and yellowish-white, mottled quartz- 
rock, becoming larger and more abundant towards bottom. Pyrolmite 
occurs in the interstices in larger blocks than in the preceding stratum 
and with cavernous spaces containing the decomposed quartz-rock. 
Decomposed quartz-rock with veins and nests of pyrolusite. 
In some of the other pits this quartz-rock or quartzite is seen to pass 
down into similar decomposed rock free from pyrolusite, and doubtless 
this passes still lower down into fresh quartzite. The iron-ore is limonite. 
Occasionally psilomelane predominates over pyrolusite in this 
decomposed quartzites, as in the following section noted by me in one 
of the old pits : — 
6" Soil. 
3' 6" Small nodules and fiat pieces of psilomelane with granules of the same. 
Also a few remains of quartzite and a little limonite. But nearly all 
more or less good psilomelane ; which, however, often shows soft 
yellowish remains of quartzite. Occasionally there is a little pyrolusite, 
which either occurs fiUing or lining cavities in the psilomelane, or, occa- 
sionally, in thin radiated crusts on the psilouielane. 
4' Decomposed white to yellow crumbly Gosalpur quartzite nvith fairly 
numerous veins of psilomelane in cracks or cavities. 
It will be judged from these sections, and is very clearly seen in the 
field, that the manganese-ore has been introduced into the quartzite by a 
process of replacement ; in which the silica of the quartzite has been taken 
into solution and manganese-ore, usually pyrolusite, deposited in its place. 
This replacement has been effected at the surface, so that there is a 
passage downwards from the ores containing very little residual quartzite 
at the surface to the decomposed quartzite containing scattered veins and 
nests of the pyrolusite, and from this into the blotched quartzite, in which 
ochre has appeared in spots as described on page 811 ; but in which man- 
ganese-ore has not yet appeared. This rock passes still lower down into 
quite fresh quartzite. The ores thus formed by this superficial replace- 
ment are of course similar in origin to those found in many other parts of 
India, as, for example, in Mysore, Singhbhum, and the Panch Mahals. 
1 Rec. G. S. 1., XXI, p. 79. 
