Chap. XIX.] 
MANGANESE IN LATERITE. 
381 
with manganese-ore at Talevadi, manganese, when present in laterite, 
usually renders itself conspicuous by segregating into forms, as a rule 
black nodules or veins of psilomelane or pyrolusite, that one would with- 
out any hesitation call manganese-orel. It rarely seems, except in very 
small quantity (or in proper manganese- ores), to become blended with the 
other constituents of laterite, so as to form intimate mixtures similar to 
those that the oxides of iron, aluminium, and titanium, so commonly 
form with one another. Indeed, many large masses of laterite can be 
found, as for example, at Mahabaleshwar and Yeruli (see page 375), that 
seem to be completely free from manganese. As it cannot be supposed 
that the rocks from which the iron and alumina of the laterite were 
derived contained no manganese, it is necessary to suppose that with 
solutions containing manganese, iron, and aluminium, a selective 
precipitation can take place in Nature, analogous to that by which iron 
and aluminium are precipitated together in the course of chemical analysis, 
whilst the manganese remains in solution. Nevertheless, in the two 
cases mentioned above (Mahabaleshwar and Yeruli), we can point to the 
possible destination of the missing manganese ; namely the concretions 
of psilomelane found in the ferruginous soil resting on the Deccan Trap 
lavas near the edges of, but at a lower level than, the base of the laterite 
caps (see page 369). In some cases, however, the manganese has 
remained in the laterite in the form of nodular concretions set in a 
matrix of ferruginous laterite. 
Of the many occurrences of lateritic manganese-ores that I have 
been able to examine, only three were in what would be called 
' laterite without any hesitation, by all geologists. These three 
Lateritoid ^^^^ low-level laterite of Goa ; in the 
high-level laterite of Talevadi in Beigaum ; 
and near Gosalpur in the Jabalpur distrit in laterite that must, I 
suppose, be called ' high-level ', although it is only at a level of about 
1 it was after Part II of this Memoir was sent to the press that I visited the 
manganese occiirrences of Sandur, Mysore, Goa, and theNilgiris. Hence I have found 
it necessary to modify this chapter considerably in places ; should any apparent 
inconsistencies be detected they must be excused as due to alterations and additions 
made whilst this part was in the press. The statement made in tlie text relative to 
the separation of manganese from iron and aluminium still holds as regards the true 
high-level laterites. In the lateritoid occurrences noticed on pages 381 — 386, however, 
the separation of manganese and iron is not always so distinct. Thus I have found in 
Mysore manganiferous limonite with the manganese apparently uniformly distributed 
through the limonite so as not to be visible as a separate constituent ; but it may still 
be stated that as a rule manganese, if present, renders itself conspicuous by segre- 
gating into veinlets and patches of some mangancse-ore such as psilomelane or 
pyrojusite. 
