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Indian Diamonds, 119
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Vindhyans, known as the Rewar group ; but this conglomerate is apparently formed of materials derived from the older or lower Vindhyan series. In Southern India the Lower Vindhyans are represented by the Karuul group and
at the very base of this formation the Diamond is found. Such is its
position, for example, at the Banagan-pilly mines. But here again the
Diamond rock is a conglomerate—that is to say, a detrital rock made up
of pebbles derived from some yet older rock. Associated with these
pebbles are the Diamonds ; but whence the Diamonds came, from what rock
they may have been broken, or out of what matrix they may have been
washed, no one can say. Old workings for Diamonds have been discovered
in the Dharwar Conglomerate, of still higher antiquity than the
Banaganpilly, but whether these workings yielded Diamonds, or not, is
unknown. If Diamonds were worked in this conglomerate their origin is
thrown back to an excessively remote period of geological time.
In
1882, M. Chaper, a French mining engineer, engaged in exploration for
Diamonds in Madras, announced that he had discovered the Diamond in its
veritable matrix near Wajra Karur, not far from Bellary. According to
his reports, submitted to the French Academy of Sciences, and to the
Geological Society of Paris, the rock which he regarded as the parent
of the Diamond, was a rose-coloured Pegmatite, but it has been shewn
that his conclusions were based on erroneous observations.
Attention
was called some years ago to the occurrence near Wajra Karur of a
certain rock, closely resembling the famous " blue earth " of the South
African Diamond fields. This "blue" forms a "neck" in a granitoid rock,
containing epidote, and associated with hornblende gneiss ; and it was
assumed that it represented an old and altered volcanic
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