1078 
MANGANESE DEPOSITS OF INDIA : DESCRIPTIVE. [ ParT IV : 
one of the southern pits the detiital accumulations are as much 
as 10 feet thick in places. Of ore in situ the largest body seen was a 
mass of very impure character (ochreous and cherty), 20 to 30 feet wide 
but the thickest definite ore-band seen was in the most northern pit 
where the section given in Fig. 83 was seen, the ore-band varying in 
thickness from 1 to 3 feet. The felspar usually shows a pearly schiller 
is a potash variety, and is^ often kaolinized. The ore-band consist 
w. s. w/ 
Fig. 83. — Section seen in a pit at Perapi. 
of psilomelane associated with yellow ochre and studded with orange-red 
manganese-garnets up to L inch diameter ; it has probably been 
produced by the replacement of the felspar of a band of spandite- 
^ felspar-rock, by manganese oxide introduced 
Spandite.felspar roe solution, the gamets being left unaltered- 
Hence the rocks here were probably once banded quartz-felspar- 
rocks of different degrees of coarseness, with a narrow band, say 2 feet 
thick, of spandite-felspar-rock. In most of the pits similar quartz- 
felspar-rock or felspar-rock is seen, usually much fresher than in the 
Kodur group of mines. In one of the southern pits there is a large 
quantity of ore formed by the replacement of 
^ ^Replaced niierocline- otherwise fresh felspar-rock. Under the micro- 
scope a section of the partly replaced felspar 
shows fresh microcline traversed by a network of psilomelane vems, 
joining together in places to form continuous patches of psilomelane. 
Besides spandite-felspar-rock, usually partly converted into 
manganese-ore, which is seen in two or three 
(rhSie).'^^'°^'"'"'°'^ pW, several pits show m siYm tough com- 
pact spandite-pyroxene-rock, the latter mineral 
