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MANGANESE DEPOSITS OF INDIA : GEOLOGY. 
[Part II: 
smooth botryoidal crusts of the same mineral and at other times with 
radiate crusts of a mineral that has not yet been critically examined, but 
which is in all probability altered manganite^. The pyrolusite may also 
be either compact or cavernous, the ca\ities usually being lined with 
crystals of the same mineral. At other times the ores are indefinite 
soft varieties that can only be designated vad. There is also a hard 
light grey crystalline mineral found associated with the other ores, 
particularly in Mysore and Sandur ; this has not yet been identified, 
and is not certainly always the same mineral. In some cases it 
seems to be probably polianite. 
Of the various ores mentioned, psilomelane is imdoubtedly the 
commonest. The nodules of this, when broken open, are frequently 
found to exhibit concentric structivres, bearing witness to the way in 
which they were formed, namely by the deposition or growth of the 
manganese oxide in layers round a nucleus of already- deposited ore. 
The mixed psilomelane-wad ores of Ramandrug in Sandur are interest- 
ing because they are often laminated, the lamination being a relic of 
the parallel structures of the slates or phyllites by the replacement 
of which they have been formed. Both in these ores and in those of 
Mysore it seems as if the wad is first formed and afterwards passes 
into psilomelane. Another variety of ore, which is not common, except 
Pisolitic (aluminous) man- in Mysore, is oolitic and made up of numerous 
ganese-oies. small rounded bodies, usually composed of 
psilomelane, and averaging 0"02 to O'Oo of an inch in diameter ; these 
bodies are set in a soft brownish-black matrix, which gives a chocolate- 
coloured streak, and to which no definite mineralogical name can be 
given. Such ore is very high in iron, and a specimen of it, analysed by 
Mr. C. Fawcitt of Shimoga, showed 33" 58 per cent, of manganese 
peroxide and 44' 16 per cent, of ferric oxide, corresponding to 
21-23 per cent. Mn and 30-91 per cent. Fe respectively. But the chief 
interest of this analysis, which is given in full on page 1138, hes in the 
large percentage of alumina, namely 13-04 per cent. ; here, in fact, we 
seem to have a case in which the manganese has not been deposited 
separately from the alumina. 
These lateritic ores differ greatly in quality from those obtained from 
the manganese-ore deposits of the Dharwar facies in the Central Prov- 
Chemical composition of inces and elsewhere. When the ore consists of 
the lateritic ores. p}Tolusite the Composition is fairly definite, 
corresponding approximately to the formula Mn02. But when the 
1 See ' pseudonianganite ' in Part I. 
