284 
MANGANESE DEPOSITS OF INDIA : GEOLOGY. 
[Part II : 
started and finished at exactly the same points of geological time, it 
will probably always be considered preferable to employ the local names 
The term 'Dhaiwar' with a general understanding as to their rough 
adopted. equivalence. When, however, it is desirable to 
treat the rocks of the different areas as a whole, it will be better to use 
the most familiar of the local names, namely Dhdrwdr, in preference 
to that which has priority on its side, but happens to be the least 
generally known of all, namely Chdmpdner^. , 
Now it so happens that, excluding the manganese-intrusives forming 
the kodurite series of Vizagapatam andGanjam, all the manganese-bearing 
rocks of any importance that have been located in the great succession of 
rocks classed as Archaean are associated with rocks belonging either to 
the Dharwars or to one of the local groups shown above to be their 
equivalents. Hence the manganiferous rocks of this type will be 
grouped together, as The manganiferous rocks of the Dhdrwdr fades 
or type. A list is given on page 240 of the areas in which manganese- 
ores have been found in rocks of this facies. 
The Deposition of the Manganiferous Sediments of the DharwSr 
Period. 
I now propose to give a general statement as to the mode of origin 
and occurrence of the manganese-ore deposits of the Dharwar facies, 
and then in Chapters XV to XVII to explain this in detail with special 
reference to the occurrences in the Central Provinces and Jhabua, the 
areas with which I am most familiar and in which the most valuable 
deposits have been so far located. 
On page 280 I have described the rocks of the Dharwar facies as 
having been deposited as a vast succession of sediments, both mechanical 
and chemical, with the contemporaneous extrusion, in some areas, of lava 
flows. The evidence of the manganese-ore deposits shows that there 
must have been many basin-shaped areas formed in various parts of 
this region of deposition. Some of these basins must have been of large 
size, of the nature of large lakes or of small seas, whilst others may have 
1 My friend and colleague, Mr. E. W. Vredenburg, in an interesting booklet 
entitled ' A Summary of the Geology of India ' (Thacker, Spink and Company, Calcutta ; 
1907), p- 17, considers that the term Ardvalli should be adopted 'as it is derived 
from one of the ujost remarkable and one of the oldest physical features of the globe. 
There is super-abundant evidence, however, that these rocks correspond with those 
known in other parts of the globe as the Huronian, and the use of a local designation 
for the Indian area is therefore .superfluous.' The treatment of the Archcean rocks in 
his book is very interesting, although I do not agree with it entirely. 
