368 
MANGANESE DEPOSITS OF INDIA : GEOLOGY. [ PaRT II : 
Manganese in tlie Lias. 
An occurrence is mentioned on page 613 of manganese- ore in a 
metalliferous vein traversing the Liassic rocks of Baluchistan at 
Shekhran in Jhalawan. 
Manganese in the Lametas. 
In the Dhar Forest and Indore State, Central India, and in the Nimar 
district in the Central Provinces, the sandstones and conglomerates of the 
Lameta formation rest on a peneplain of Bijawar, and metamorphic 
and crystalline, rocks. The former (Bijawars) appear to have undergone 
a sort of lateritization in pre-Lameta times on lines analogous to the 
process by which the post-trappean laterites have been formed. This 
pseudo-laterite has been designated ' porous breccia ' by Mr. Vredenburg, 
and is composed of angular fragments of quartz, hornstone, quartzite, 
etc., set in a soft porous, loamy, matrix. The lowest Lameta beds 
probably consist of this porous breccia rearranged by water, so that it 
is often impossible to decide where the latter ends and the Lametas begin. 
The argillaceous-sandy matrix of this breccia is often replaced by manga- 
nese oxides (pyrolusite or psilomelane) so as to yield a breccia of angular 
fragments of white quartz set in a black matrix of manganese oxide. 
The Lameta sandstones and conglomerates, where porous, have also 
often been impregnated by oxides of manganese, and where the sand 
grains and pebbles were originally set in an argillaceous matrix, the latter 
has often been replaced by psilomelane. No cases have yet been found 
of undoubted original manganese oxide in the Lameta rocks, except per- 
haps in the re-arranged manganiferous breccias sometimes forming the 
base of this formation ; for they may have been rendered manganiferous 
either before or after the deposition of the Lametas. The ultimate source 
of the manganese that has brought about the impregnation and re- 
placement of Lameta rocks is probably to be looked for in the meta- 
morphic and crystalline rocks in the areas in which these rocks occur. 
For even if there are no manganese-silicate minerals, properly so called, 
in these rocks, the ferro-magnesian silicates always contain small quan- 
tities of this element. As to when the Lametas and porous breccias 
became impregnated with manganese oxide it is impossible to speak 
with certainty, but it seems likely that this took place in pre-Trappean 
times, when the metamorphic and crystalline rocks were uncovered 
and freely exposed to the action of meteoric waters. For details of 
