298 
MANGANESE DEPOSITS OF INDIA : GEOLOGY. [PaRT II 
district of the Central Provinces, whilst on pages 168 to 172 of the same 
paper I have discussed the origin of these rocks. The crystalline lime- 
stones are there divided into three groups as foUows : — 
1. Limestones containing some or all of the following accessory 
minerals : — diopside, hornblende, tremolite, quartz, epidote, 
essonite, sphene, magnetite, and mica. 
2. Manganiferous limestones, often containing spessartite and 
rhodonite, and black in coloiir due to the deposition of man- 
ganese oxide along the cleavage and twinning planes of the 
calcite. 
3. Serpentinous limestones and cipolhnos, usually dolomitic, and 
resulting from the chemical alteration of original white 
pjTOxene-rock, sometimes containing phlogopite, and, 
more rarely, spinel and chondrodite. 
It is not necessary to consider here whether the rocks from which 
the limestones of Class 3 are supposed to have been derived are of Dhar- 
war age, or a portion of the more ancient platform on which the Dharwar 
sediments were deposited ; for they have no connection with the man- 
ganese-bearing rocks. The Arch.ean rocks of this district have been 
so metamorphosed that they have all been mapped together as the 
metamorphic and crystalline complex, and no attempt has been made 
Dharwars in the to distinguish the portions of this complex that 
Chhindwara district. are to be regarded as the equivalents of the Chilpi 
Ghat series of the Balaghat district, that is the portions that are of 
Dharwar age. Consequently in the above-mentioned paper neither 
of the terms Chilpi and Dharwar was used. It seems probable, however, 
that, of the rocks given in the classification on page 167 of that paper, 
Groups IV and V, and a portion of Group III, are to be regarded as 
belonging to the Dharwar system ; whilst, as Avill be explained below, 
the probability is that Groups VI and VII and the first two sections of 
Group VIII also belong to this same series of rocks. 
The evidence put forward in that paper is held to justify the con- 
The origin of the clusion that limestones of Class 1 (above) have been 
ineSses and" crystal- ^ovmed by the chemical alteration of rocks similar to, 
line limestones. or identical with, a group of rocks there called the 
quartz-pvroxene-gneisses. No analysis has ever been made of these 
gneisses, but a glance at the list of minerals they contain is sufficient 
to show that they may easily have been produced by the metamor- 
phism of impure calcareous sediments. The alternative to this is to 
