654 
MANGANESE DEPOSITS OF INDIA : DESCRIPTIVE. [PaRT IV : 
page 657), it is possible that in addition to the ore formed by superficial 
replacement there is some representing origmal manganiferous sediments 
since compacted ; but of this I have seen no evidence myself. And con- 
sidering the large bodies of manganese-ore in the Sandur Hills that have 
been in all probability formed by superficial replacement, it does not seem 
improbable that all the ore of Sivarajpur has been formed in the same way. 
If so, then it must not be expected to continue of good quality below a 
depth of, say, 100 feet, if so far. Moreover, the ores are as a rule very 
impure owing to the presence of small residual patches of the original 
quartzite or slate that have escaped replacement. 
With regard to the source of the manganese that gave rise to the man- 
Souice of the ganesc-bearing solutions by the percolation of which 
mangrtnesc. the replacement of the quartzites and slates must 
have been brought about, it is probable that it lies in the Dharwar rocks 
themselves, as, for example, in the form of an midiscovered bed of slightly 
manganiferous hematite, or even in the slates, which no doubt contain 
traces of this element. 
The ores consist of pyrolusite, and what looks like psilomelane at rirst 
Mature and quality sight, the latter ore being by far the commoner. On 
of the ores. close examination this latter ore is seen, however, to 
contain minute shining specks suggesting the presence of braunite. That 
braunite is present is shown by the complete analysis of a hand-specimen 
given on page 656, and also by the partial analyses of samples on pages 
657 to 660, for in these also the silica has been separated into fre and 
combined. In the bulk samples the braunite ranges from 8 to 24 per 
cent, and in the complete analysis of a hand-specimen it is 42 per cent. 
The ores are often very impure owing to the presence of small residual 
patches of the original quartzite or slate that have escaped replacement ; 
but such ores would of course be rejected in working the deposits. 
The limits and average values of the constituents of commercial value 
in the samples taken by me are as follows : — 
Limits. 
Mean. 
Manganese . . . . ' 
30-20 to 49-35 
41-68 
Iron .... 
3-05 to 6-25 
4-07 
Silica (total). 
2-80 to 40-65 
19-M 
Phosi)horus 
0-16 to 0-25 
0-20 
Moisture at 100°C. 
0-30 to 0-40 
0-35 
