Chap. XX.] 
MANGANESE-ORE PISOLITES. 
391 
ordinary succession, as seen in a section of a deposit being quarried in 
the alluvium, is an overburden of alluvial clay resting on a detrital 
accumulation of fragments of manganese-ore mixed with pieces of the 
accompanying rocks. The fragments in these detrital accumulations 
vary from very small dimensions up to pieces several inches in diameter, 
the tendency being for the fragments to increase in size as the ore in 
situ is approached. It is these detrital accunmlations that are 
designated in various parts of this memoir as the talus-ore deposits. 
Sometimes these talus-ore deposits rest directly on the ore-body, but 
as often as not they are separated from the ore-body by a certain 
thickness of the pisolitic grarel. Thus at Kandri such an intervening 
layer of manganese-ore pisolites, about one foot thick, is to be seen 
in many of the pits in the talus-ore deposits. When the pisolites are 
broken open they are found, as before, to be some of them of detrital origin 
and some of concretionary origin. 
The origin of the detrital fragments in all these difTerent cases is easy 
OriEin of the detrital to follow. Thus, in the case of Kurmura, the 
pisolite.s. rolHng of small fragments down the hillside and 
subsequent movement in every heavy shower of rain over the surface 
where they now lie is sufficient to account for their present rounded 
condition. It is easy, moreover, to conceive of such mechanically 
rounded fragments becoming enclosed in alluvial clay. In the cases in 
which these pisoHtes are found between the ore-body and the talus-ore 
deposits, it is necessary to suppose that first the pisolites collected on 
the surface of the ground in the same way as they are now found at 
Kurmura, and that later the talus- ores covered them up. Many of these 
pisolites, both detrital and concretionary, are also found between the 
fragments of manganese-ore composing the talus-ore deposits ; as before 
the origin of the detrital pisolites is easy to understand. 
The origin of the concretionary pisolites in these different cases 
Origin of the concretion- is not SO simple. Briefly stated, however, 
ary pisohtes. [i is probable that circulating surface waters 
dissolved a certain quantity of manganese from the manganese-ore 
bodies or their detritus and subsequently deposited tliis manganese 
wherever the conditions were favourable. All that would be necessary 
for this process to take place would be for the ground waters to 
contain either carbon dioxide or organic acids in solution. Such 
waters, on coming in contact with manganese-ore, would take certain 
quantities of manganese into solution. This m'ght be deposited in 
