- CHAPTER XIV. 
I-' 
GEOLOGY— continued. 
The Manganiferous Rocks of the Dharwar Facies, 
including the Gondite Series. 
General — Deposition of the Dharwar manganiferous sediments — Their partial 
metamorphism — Their more complete m-tamorphism — The alteration of the 
manganif rous silicates — Mineral vein-^ and intrusives — Manganese-ores in crys- 
talUne limestones — Classification of the Dharwar manganese-ores. 
General. 
It has already been mentioned that the formation of the oldest 
The Dharwar period gneisses must have been followed by a period of 
of sedimentation. mechanical Sedimentation characterized by the 
deposition of sands, clays, and conglomerates. During the same period 
various chemical sediments must also have been deposited, particularly 
limestones, and possibly various ferruginous rocks, such as hmonites. 
The period of tectonic quiescence during which these sediments 
accumulated must have been of considerable duration, and the sediment- 
ation must have been interrupted at intervals by the eruption of con- 
temporaneous lava-flows. Although the general period of sediment- 
ation must have the same over the whole of what is now the Peninsula 
of India, yet it does not follow that this period of sedimentation 
began and ended at the same time in the various parts of the 
area. The whole of the series of sediments thus formed was then 
^ , . subiected to intense tectonic disturbances, by the 
The ruetatuorphism J r i ■ t i t j- i t i • • i 
of th sediments. action of which the sediments were folded in with 
the oldest gneisses more or less deeply and subjected to various degrees of 
metamorphism and consequent mineralogical and structural changes ; the 
degree of metamorphism produced naturally depending on the depth to 
which the particular sediments were folded in, that is on the intensity of 
the pressure and temperature to which they were subjected. In some 
cases this metamorphism was so pronounced that it is now extremely 
difficult to separate these rocks from the older rocks with which they are 
associated, so that the sediments of this period have to be mapped with 
the other Archaean rocks as the metamorphic <md crystalline complex, 
as in the districts of Balaghat, Bhandara, Chhindwara, and Nagpur, in 
the Central Provinces, and in Narukot in the Bombay Presidency. In 
