902 
M VNGANESE DEPOSITS OF INDIA : DESCRIPTIVE. [PaET TV : 
than corresponds to the true width of tlie ore-band. Since tlie above 
was written, a cross-cnt 2G9 feet long has been made riglit across the 
ore-ridge, wliich 1 was able to examine in December 190(5. This show s 
a succession of huninated and schistose rocks dipping at angles vary- 
Seciion km-ii in a ing from 15° to 50° to the south side. The most 
(loss- cut. abundant rocks are mica-sdiists, of both fine and 
moderately coarse grain, and schistose micaceous gneisses. Interbedded 
with these, es])ccially with the schists, ai-e subordinate layers of 
spessartite-quartzites, sandy schists, black vitreous quartzite, and 
finally the most important of these subordinate rocks, a whitish, very 
fine-grained rock, sometimes very soft and friable and sometimes hard 
and jaspery in appearance. This rock is very similar in appearance to 
the Dharwar jaspers of Jabalpur and the Panch Mahals, but Avas found 
on microscopic examination to be a very fine-grained spessartite-quartz- 
rock or gondite. There are also, about the middle of the cutting, and 
thus corresponding to the highest part of the ridge, tw^o bands of 
manganese-ore each 7 feet thick, separated by about 12 feet of mica- 
schists and other rocks. 
There are also other smaller bands of ore evidently formed by the 
more or less complete replacement or alteration of the light coloured 
rocks. In this replacement or alteration the rocks most afTected seem 
to have been the gondite layers, corresponding to each of which there 
is consequently a dark streak in the walls of the cutting. The mica- 
schists have also been to a small extent affected, frequently shewing 
thin veins and small spots of manganese oxides. AVlien the main ore- 
bands are examined they also are found to be partly due to the alteration 
of gondite, but I could not determine if any of the ore was original. This 
alteration or replacement was distinctly more complete at the surface 
than lower c1o\mi. 
Intrusive in the rocks seen in this cutting are some masses and veins 
Felsjjathic intru- of felspar-rock sometimes containing j^ellow crys- 
tals of garnet, presumably spessartite. In one 
place there was a veinlet lying parallel to the bedding of the ore-band, 
only a yard long, .3" thick at the middle, and dying out lenticularh' 
at either end. This veinlet contained a vug in which were developed 
idiomorphic crystals of felspar up to | inch in diameter and showing 
the following forms: — (110), (001), (010), (101), and a negative hemi- 
orthodome. Since the felspar-rock is often partly replaced by manganese- 
ore it must have been intruded into the other rocks before the 
secondary ores were formed, but after the foliation of the rocks and 
consolidation and metamorphism of any original manganese-ores. For the 
source of the manganese that brought about the replacement ^ve must 
look to the spessartite-bearing rocks. Another interesting .structural 
feature is well seen in this cutting. Each band of ore, instead of 
