1118 
MANGANESE DEPOSITS OF INDIA : DESCRIPTIVE. [ PaRT IV : 
character and showing a considerable resemblance to laterite. The out- 
crops, especially, have the same rugged cavernous aspect, and are 
usually lichen-covered. The manganese-ores in the lateritoid are usually 
psilomelane, with often some wad and pyrolusite. The lateritoid often 
shows remains of the underlying rocks, quartzite, lithomarge, or 
jjhyllite, and the examination of a considerable number of sections has 
led me to the conclusion that this lateritoid has been formed by the super- 
ficial alteration and metasomatic replacement of the rocks corresponding 
to the altered rocks now found beneath the lateritoid. These altered 
rocks consist of interbanded lithomarges of various colours, ochres, 
wads, and decomposed quartzites. The quartzites often contain a con- 
siderable quantity of pyroluside in the form of nests and patches formed 
by impregnation and replacement ; whilst in the lithomarges, 
ochres, and wads, there are often considerable quantities of concretion- 
ary psilomelane. The lithomarges probably correspond to original 
phyllites and slates, and probably suffered alteration to their present 
condition at the same time as the lateritoid was formed, and as a pait of 
the same series of changes. The evidence for the statements given above 
is scattered through the descriptive accounts of the deposits in the 
following p)8ges, but attention may be directed to the accounts of the 
Bikonhalli, Sadarhalli, and Tumkur deposits, as affording the best evid- 
ence on these points. Since the Mysore deposits bear considerable re- 
semblance, at least in mode of formation, to those of the Sandur Hills, it 
is not necessary in this place to go further into their origin. Most of the 
points considered in the account of the Sandur deposits apply here. 
I have, however, treated the question more fully under the heading of 
the Shimoga district. 
As will be judged from the account given above of the way in which 
the ores occur, they are as a rule distributed in a very pockety and un- 
certain manner, the only exception that I saw being the Kumsi deposit. 
They are also all superficial in character and will not be found to continue 
to any considerable depths — rarely below 50 feet, and often to nuich 
smaller depths only. The chief difference between these deposits and 
those of Sandur is that, with the exception of Kumsi, none of the deposits 
I saw seemed to be of any considerable size. 
In addition to psilomelane, pyrolusite, and wad, the Mysore deposits 
often yield the light grey crystalline mineral found in Sandur (in one 
case — Bikonhalli — doubtfully identified as polianite), and occasior.ally 
pseudo-manganite. 
