312 
MANGANESE DEPOSITS OF INDIA : GEOLOGY. 
[Part II : 
and granite are found weathering out at the surface of the supposed 
gneiss. On breaking the rock at such places it is found that the pro- 
jections are in truth pebbles. They are composed of various materials, 
white quartz, granite, and gneiss, and are set in a matrix ha\'ing the 
ordinary mineralogical composition of a micaceous gneiss. Under the 
microscope this matrix is seen to be much strained and granuhtized 
and composed of quartz, microcline, plagioclase, and biotite. with often 
muscovite. The conclusion that seems unavoidable is that this con- 
glomeratic gneiss is only a metamorphosed conglomeratic grit, no doubt 
very impure, equivalent to the rock of this character, already 
schistose, that underlies the ore-band at Biilaghat. That such a 
rock can be formed by the metamorphism of an impure grit has 
been conclusively shown by E. H. Cunningham- Craig ^ writing of the 
rocks of the Loch Lomond district in Scotland. He shows that albite- 
gneisses have been formed from the group of rocks known as the 
Beinn-Ledi Grits by dynamic and constructive metamorphism. We 
seem to have in the Balaghat district an analogous case, the only difference 
of note being that in the area examined by Cunningham- Craig the increas- 
ing metamorphism has taken place across the strike, on passing from 
one fold of the grits to another that has been subjected to a higher degree 
of pressure, and to a certain extent, temperature ; whilst in the Balaghat 
district the passage from grit to gneiss has taken place along the strike. 
We thus see that the rocks of Balaghat and Ukua can be correlated as 
follows : — 
Balaghat. Ukua. 
1. Phyllites with subordinate slates and 1. Mica-schists. 
mica-schist.s. 
2. Manganese-ore layers with inter- 2. Manganese-ore layers associated with 
banded vit;eous quartzites and bands of si)essartite-quartz-rock ar.d 
occasional phyllites. of vitreous quartzites. 
.3. A small ihickness of jaspery quartzite. 3. A small thickress ci jas]eiy quailzile, 
sho^^ing. on weathering, signs of 
schistosity ; not always present. 
4. Schistose conglomeratic sericitic grit. 4. Schistose micaceou s gneiss often con- 
taining pebbles of quartz, granites, and 
gneiss. This rock passes downwards 
into less schistose gneiss. 
The gneiss underlying the manganese-ore band at Ukua would ordinarily 
get mapped as distinct from the Chilpis and as a part of the metamor- 
1 Quar. Jour. Oeol. 8oc., LX, pp. 10-28, (1904). 
