738 
MANGANESE DEPOSITS OK INDIA : DESCRIPTIVE. [PaRT IV : 
the partial replacement of tlie rock by mangancse-ore. This rock also 
contains a bro^vn pyroxene. In another much finer grained variety of 
the rock there is a great abundance of this pyroxene, which under the 
microscope is pleochroic in brownish orange and yellow. The roclv also 
contains a little bronze-coloured mica having an optic axial angle of about 
32°. 
Hillocks 3 and 4. 
The top of hillock 3 is E. 25° N. from that of 2. The outcrop 
of the ore-band here is prominent, almost forming 
a wall. The ore itself is a speckled and rather softer 
variety composed of a small proportion of braunite in a cavernous matrix 
composed partly of soft black oxides, partly of shiny lead-like psilome- 
lane, and partly of the ordinary dull grey psilomelane ; but there is also 
some of the harder ore. This ore is mostly free from extraneous materials, 
but in places contains a little spessartite and bronze-coloured mica. The 
ore on hillock 4 is very similar to that on 3, but a larger proportion of it 
contains the bronze-coloiired mica. 
A sample was taken from the outcrop on hillocks 2, 3 and 4, and con- 
sisted largely of the above-mentioned speckled 
variety, with a certain amount of psilomelane and of 
the hard grey braunite-psilomelane mixture. The analysis made at the 
Imperial Institute shows : — 
Nature and quality 
of the ores. 
Sample No. 45 
Manganese peroxide 
Manganese protoxide 
Ferric oxide . . 
Silica (combined) 
Silica (free) 
Phosphoric oxide 
Moisture at 100° C. 
53- 
06 
22 
91 
14 
04 
2 
02 
0 
67 
0 
31 
0 
70 
This is equivalent to :- 
Manganese 
Iron 
Silica 
Phosphorus 
Moisture 
51-33 
10-25 
2-69 
0- 135 
0-70 
and indicates the presence of about 20 % of braunite. 
The characteristic of these Kosumbah ores is seen to be a low % of 
braunite and consequent low % of silica, a high % of iron and rather 
high % of phosphorus. 
