Chap. XXt ] 
SATARA DISTRICT. 
^63 
In every case the manganese-ore seen was concretionary psilomolane 
Modo of occuirenco of botryoidal and other shapes. These concretions 
and origin. ^vere either lying loose on the surface, or were con- 
tained in 1 to 3 feet of reddish or brownish clayey soil, resting imme- 
diately on crumbly beds of soft greyish or reddish trap containing decom- 
posed felspar phenocrysts and a copper-coloured micaceous mineral. 
It is a curious fact that, with one doubtful exception,! nowhere was 
any trace of manganese-ore seen associated with the laterite so abundant 
at both Mahabaleshwar and Yeruli. The soil containing the manganese 
concretions was in every case situated at a slightly lower level than, and 
not far from the edge of, the base of the laterite cap. 2 
There can be no doubt that the laterite, often very aluminous, of 
this district, has been derived in past times, at least in part, by the 
chemical alteration of beds of lava similar to those now immediately 
underlying the laterite. This process has consisted in the main of a 
concentration of oxides of iron, aluminium, and titanium, and of a 
removal of silica. Judging from the evidence of the mansanese-ores 
occurring in the laterite of Belgaum, Bidar, and Jabalpur, the tendency, 
when a rock becomes lateritized, is for any manganese it contains to 
segregate into veins, patches, and nodules, in the laterite. In this case 
the manganese, which the traps no doubt contain in small quantities, 3 
has, instead of being concentrated in the laterite, apparently been 
removed, and the question arises as to whether the psilomelane 
concretions occurring in the above-mentioned manner may not 
indicate the destination of this manganese. The psilomelane nodules 
of Chikhli contain little specks of a soft greenish material similar to 
that occurring in the underlying decomposed crumbly red trap ; this 
indicates that the soil arises from the direct decomposition of the traps 
and that when the other constituents are removed by meteoric agencies 
the manganese segregates in the residual ferruginous yoil, no doubt using 
portions of the trap as nuclei. With the access of more and more man- 
ganese, such portions of the traps as become enclosed in the manganese- 
1 In a little ravine near the Yenna Falls I found a pebble of possible lateritic origin 
composed of pisolites of wad — averaging i to J inch, but ranging up to nearly 1 inch, in 
diameter — set in a red ferruginous clay. 
2 The heights above sea-level of the various occurrences of manganese-ore, as taken 
with an aneroid, varied between 4,050 and 4,350 feet. 
3 As an exceptional example of manganese occurring in the traps, I may mention 
a lavender-coloured earthy lava from the Mahableshwar-Pratapgad road, mile-stone 
84, containing abundance of heulandite and of included fragments of .scriiaceous lava. 
Some small dark blackish fragments included in this lava give a decided reaction for 
manganese-ore, on fusion with nitre and fusion mixture (28 53 in Eock Register). 
