Chap. Xf J. ] 
CHITALDRUG : SADARHALLI. 
1123 
produce the effect of a mixture of brown and white qaartzite. In 
this quartzite nests of pyrolusite are often found, there being every 
stage between the fresh quartzite, through quartzite blacken^^d by 
the deposition of thin fihns of manganese oxide round each separate 
quartz grain, to pyrolusite in which all the quartz has been replaced 
by manganese oxide. The quartzite that is being replaced by manga- 
nese oxide has often become affected so that the grains of quartz 
have all become separate and the rock all tumbles into a fine white 
quartz sand on being handled. The lithomarges are sometimes seen 
to retain traces of slaty or shaly structure, and in places, instead 
of lithomarges the rocks underlying the lateritoid are seen to be 
laminated rocks suggesting altered slates or phyllitos. Although there 
is some merchantable psilomelane associated with the lithomargic rocks, 
and Some merchantable pyrolusite associated with the decomposed 
quartzites, yet the main mass of the manganese-ore worth extracting is 
in the lateritoid, where it occurs mainly in the form of psilomelane, 
mixed in varying proportions with limonite. This lateritoid often 
shows residual quartzite or slaty rock, so that it seems that it is the 
final product of the process of alteration and replacement that has 
evidently affected the whole of the mass of rocks situated near the 
surface of this hill. From the mode of occurrence of the ores it will be 
seen that they are only to be found near the surface, and that f s the 
workings are deepened it will probably be found that the manganese- 
ores decrease in quantity and finally disappear. They will probably be 
found to extend deepest along the bands of quartzite, which seem to be 
more susceptible of replacement than the argillaceous rocks. Although 
the total quantity of ore in this hill cannot be large, yet I shall not be 
surprised if as much as 10,000 tons be extracted. The strike of the 
rocks revealed in the pits is generally N. N. W. to N. W., with the dips 
sometimes to the east and sometimes to the west side of the strike. 
In one place the lateritoid is very interesting. On the south slope, 
extending to some 50 feet below the summit of the hill, is a big outcrop 
of the lateritoid. At the base of this outcrop 
Interesting forms of . , „ i • r, 
lateritoid. there IS a shallow excavation showing a soft 
rock composed of manganese- ore pisolites set 
in a soft clayey matrix of dark brown colour. This gives way above to 
ferruginous rock composed of red-ochre pisolites in a matrix of red ochre, 
IV 2 L 
