384 
MANGANESE DEPOSITS OF INDIA : GEOLOGY, [ PaRT II t 
shows a white decomposed friable sandy rock which, from exposures elsewhere, is 
regarded as a decomposed biotite-quartz schist. This passes upward without any 
abrupt change through a buff sandy clay to a reddish buff, soft rock containing 
small indistinct ferruginous secretions and minute manganese nodules. As the 
surface is approached the rock gradually acquires depth of colour, while the con- 
tained manganese secretions become larger and better defined until, at the surface, 
they are 2 to 3 feet across with e like depth. With increase of ferruginous content, 
the rock becomes so hard that, at the surface, it is often necessary to use explosives 
to disintegrate it. A few feet below it can be cut with a spade. Through the 
manganese secretions there ramify veinlets of gibbsite ' 
-<II>- 
-0 iSh 
Fig. 22. — Typical Section of Laterite, Talevadi, Belgaum. 
(1) Psilomelane with gibbsite veinlets. 
It is interesting to note that in the Jabalpur district, the main 
^ ^ , ^ ^ portion of the ores has been formed by 
Jabalpur and Goa. ^ _ r i j. J 
superficial replacement or slates ana 
quartzites, and is to be classed as lateritoid ; but there is also some 
laterite (at Gosalpur) in which pyrolusite is in places found. In Goa 
some of the manganese-ore is in the laterite itself ; but the quarries 
for manganese also show that the manganese extends mto the under- 
lying Dharwar rocks, where it has evidently been formed by the 
same process of superficial replacement. There seems^ moreover, to 
be a passage upwards from the quartzite or slate through the 
mixture of manganese-ores or iron-ores, and residual quartzite or 
slate, to the overlying laterite. This overlying laterite, which is 
