Chap. XVIII.] 
DECCAN TRAP. 
369 
the occurrences of manganese in the Lametas and porous breccias see 
the accounts given under the headings of the States and districts 
of Dhar, Indore, and Nimar. 
Manganese in the Deccan Trap. 
It is probable that small quantities of manganese are fairly uniformly 
distributed through the lavas of this formation, these rocks being usually 
basic. No analyses of these lavas have, however, ever been published, 
so that it is not possible to say what this quantity will average ; but 
probably, as is usual in basalts and dolerites, only a few tenths of one 
per cent. Manganese-ores have been reported to occur in the districts of 
Amraoti, Belgaum, Dharwar, Ratnagiri, and Satara, but nothing further 
has been heard of any of these ores except those of the Satara district. 
At Mahabaleshwar in this district, where the Deccan Trap formation 
reaches almost its highest elevation above sea-level, there are several 
occurrences of concretionacy or nodular psilomelane, usually in a red- 
dish clayey soU. The interesting feature of this occurrence is that the 
higher parts of the Mahabaleshwar plateau are covered with laterite, in 
which I was not able to find a trace of visible manganese oxide, the ores 
always occurring in the above-mentioned soil where it overlies the 
decomposed trap at the edges of the laterite cap. From the fact that the 
manganese- ores are sometimes found to contain remains of substances 
probably once contained in the trap it is probable that the concretions 
of manganese-ore, and the soil in which they occur, have been formed 
by the decomposition in situ of the trap rocks with the concentration of 
the manganese. Since, however, the laterite covering most of the higher 
parts of the plateau must also have been derived from the trap rocks by 
their chemical alteration, in a way that does not matter here, and since, 
as already mentioned, this laterite seems to be free from manganese, 
it is evident that a considerable amount of manganese must have been 
removed in solution from the trap rock from which the laterite has been 
produced. It may be that this manganese has also found a resting place 
in the soil resting on the decomposed surface of the trap. If this be 
the case then the manganese concretions in this soil may have derived 
their manganese from two distinct sources, namely (1) from the rocks by 
the decomposition of which the soil has been produced, and (2) from the 
masses of rock from which the laterite of the higher parts of the plateau 
has been formed. For further details about these occurrences of ore, 
see the account of the Satara district (pages 661—668). 
II K 
