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MANGANESE DEPOSITS OF INDIA : GEOLOGY. [ PaRT II : 
favourable circumstances to furnish tlie requisite quantities of manga- 
nese. It so happens, however, that there is in India a series of rocks, 
namely the kodurite series of Vizagapatam, that contains an unusually 
large amount of manganese as an essential constituent of its garnets 
and pyroxenes. There is no evidence available to show the relative 
ages of the kodurite and the Dharwar series, but we must not lose 
sight of the possibility that the manganese deposited in Dharwar times 
was derived, not from the small quantities of this element contained in 
the ferro-magnesian silicates of such ordinary rocks as granites or 
diorites, but from rocks specially rich in manganese ; and, if not actually 
trom the kodurite seiies, then from some other series of rocks, equally 
nch in manganese, that has either been entirely buried beneath 
later rocks, or is in existence somewhere at the surface and yet awaits 
discovery. 
The Partial Metamorphism of the Manganiferous Sediments. 
After this vast succession of sediments had accumulated, or perhaps 
towards the end of their deposition, they (and all the older rocks) were 
involved in a prolonged and severe tectonic disturbance, which folded 
them in with the older rocks, and produced in them varying degrees 
of structural and mineralogical change according to the depth to 
which they were folded in, and consequently according to the in- 
tensity of the pressure and heat to which they were subjected. When 
the intensity of this metamorphism was not very great the clays were 
simply converted into slates or phyllites (usually referred to as argilUtes 
in Southern India) ; the sands were converted into quartzites or sand- 
stone -quartzites of varying degrees of induration, often assuming jas- 
peroid or homstone-like characters, perhaps due to partial chemical 
solution and re-deposition ; whilst the conglomerates were rendered 
more or less schistose. Any ferruginous sediments were converted into 
hematite, and less frequently into magnetite, thus giving rise to the 
Formation of pn- banded hematite-jaspers, often containing mag- 
mary ores. netite, that are so characteristic of the Dharwars. 
Any bands of manganese oxide that were contained in these sedi- 
ments were compressed and rendered crystalline. The ores so formed 
may be termed primary ores. The rocks of the Dharwar facies that have 
suffered this amount of metamorphism are the typical Dharwars of Dhar- 
war, Bellary, and Mysore, the Dharwars of Singhbhum and Jabalpur, the 
Chilpis of Balaghat, and the Champaners of the Panch Mahals. Of 
