Chap. XIX.] 
MANGANESE IN LATERITE 
387 
of the Dharwar series, which is the manganese-ore bearing series 
of India far excellence, is often very rich in this mineral. 
The similarity between deposits of manganese-ore in the true 
laterites, as in Goa and Belgaum, and those in lateritoid, as in Mysore, 
is so great, that the remaining paragraphs of this chapter can be taken 
as applying to both, bearing hi mind that the Sandur deposits, and that 
of Kumsi in the Shimoga district of Mysore, are not typical of the whole. 
Since the manganese -ores found in laterite usually take the form 
The structure and work- ^f boidders, nodules, and other concretions, set 
ing of the lateritic manga- in a matrix of ordinary ferruginous laterite, it 
nebc-ore deposit... foUows that in working them there will be a 
much larger proportion of waste per ton of ore extracted than in the 
case of solid bodies of ore, such as some of those of the Dharwar type 
being worked in the Central Provinces. But this disadvantage is to a 
certain extent neutralized by the fact that the lateritic ores, owing to 
the comparative softness of the matrix in which they are set, can 
usually be quarried with greater ease than the massive ores of the Central 
Provinces. The lateritic deposits are further distinguished from those of 
the Dharwar type by the fact that laterites and lateritoid, the rocks 
in which they occur, are only found at the surface, where they are 
disposed in more or less horizontal masses tending to be bed- like ; 
these, as mentioned on a previous page, are rarely of a greater 
thickness than 100 feet, and usually much less. The distribution of the 
concretions of manganese-ore is, moveover, very irregular, so that a given 
mass of laterite or lateritoid may be very rich in ore at one point, and 
close by contain insufficient ore for the deposit to be worth working. 
The consequence is that the lateritic deposits are of much more uncertain 
character than the deposits of the bedded type, as exemplified by the 
Dharwar deposits of the Central Provinces ; and hence of much less 
value. 
The manganese- ores found in laterite and lateritoid usually consist 
either of psilomelane, or of pyrolusite, or of mixtures of the two. V/ith 
The mineral composition these, limonite and ochreous hematite are often 
of the lateritic ores. intimately associated; and, when the iron-ores 
cannot be readily cleaned away, the manganese-ores are rendered 
valueless, unless a market can be found for manganiferous iron- ores 
containing a comparatively small amount of manganese. The psil- 
omelane is often concretionary in shape, being either reniform, botryoidal, 
or mammDlated. Sometimes it is compact and at other times caver- 
nous. The cavities in the latter type of ore are sometimes lined with 
11 L 2 
