Chap. XXXV. ] 
JABALPUR DISTRICT. 
811 
often present in the hematite, all tlicse substances being carried away in 
solution, and the interchange being probably, at least in part, metaso- 
matic. This process of concentration of manganese and removal of iron 
continuing for a long time results in the fina! change of the whole out- 
crop into psilomelane boulders and nodules, resting upon mangani- 
ferous hematite veined with psilomelane, with this passing gradually 
downwards into unaltered hematite. 
Turning now to the Gosalpur group, which Bose supposes to underhe 
„ , , the Sihora beds, we find it to be composed 
The Gosalpur quai tzites. _ ^ ^ 
principally of quartzites varying greatly in 
colours, various shades of white, brown, grey, yellowish, and reddish 
prevailing. In texture they are usually very fine-grained, sometimes 
fine enough to be called jaspers, and typical red jasper is not an uncom- 
mon rock in this group, e.g., at Mangeli. Occasional thin partings of 
micaceous hematite are also found in these quartzites at places. The 
Gosalpur quartzites show bedding but seldom, and are very frequently 
brecciated at the surface, showing angular fragments of quartzite set in a 
matrix that may be limonite, pyrolusite, psilomelane, ochre, or chert. 
In some cases this brecciation strongly suggests the fault breccias that are 
so common in the Dhar forest and elsewhere ; this especially applies to 
the breccias with a chert matrix. But in the majority of cases this brec- 
ciation is only superficial and is due to chemical changes affecting the 
rock, and possibly taking advantage of cracks. A very common way in 
which this change takes place is as follows. In the white quartzite, for 
example, tiny round yellow spots appear, often arranged in bands, and 
these spots become more and more numerous, finally joining together so 
as to produce a soft sandy yellow rock in which are enclosed unaltered 
areas of the original quartzite. These being usually angular in area 
impart to the rock the aspect of a fault breccia of white quartzite set in 
a soft sandy or ochrey yellow matrix. This rock is seen in many of 
Mr. Bose's pits at Gosalpur and elsewhere to pass downwards in the course 
of a few feet into unbrccciated, and but sUghtly altered, quartzite. 
It is in association with the Gosalpur quartzites that the pyrolu- 
Pyrolu«ite ^^^^ ^^^^ district is usually found. The 
relationship of the pyrolusite to the quartzite 
is well seen in many of Mr. Bose's pits at Gosalpur. 
