Sec. II, Ch. 7: The Indian Diamond

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	Indian Diamonds, 119

	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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