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Sec. II, Ch. 2: The African Diamond

Sec. II, Ch. 2: The African Diamond Page of 366 Sec. II, Ch. 2: The African Diamond Text size:minus plus Restore normal size   Mail page  Print this page
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African Diamonds.
speculate as to the possible effects of further metamorphosis upon the graphite, and have thus dimly seen in the vegetable fossils of the karoo formation the ultimate origin of the South African Diamonds. Quite recently Dr. Friedländer has suggested, on experimental evidence, that the Diamonds may have been formed by the action of a molten silicate, like olivine, on graphite ; and the late Prof. Carvill Lewis held that the South African Diamonds had probably been formed by the action of an olivine rock, or peridotite, on the carbonaceous matter of the karoo shales, Many other observers, however, are disposed to refer the Diamonds to a much deeper subterranean origin.
In certain places the lacustrine shales and sandstones of the karoo-formation are cut through by dykes or veins of various eruptive rocks, known popularly as " trap ; " whilst in other places similar igneous rocks are spread out in sheets, intercalated between the sedimentary strata. Varying considerably in their characters in different local­ities, some of them exhibit a vesicular texture, and contain in their bubble-like cavities kernels of Chalcedony, Agate, Jasper, and other siliceous minerals. By the disintegration of such rocks, the hard Agates and kindred stones are set free, and carried down as pebbles by the rivers. Indeed the shingle of the Orange and Vaal Rivers has long been famous for the beauty of its Agates and other pebbles. In addition, however, to these attractive chalcedonic pebbles, the shingle contains a great variety of other minerals, among which there is one of paramount interest—the Diamond itself. It was in the agate-bearing gravels of the Vaal and Orange Rivers that the Diamond washer origin­ally established his "river-diggings."
The search for Diamonds along the Vaal River com­menced in 1868. According to Mr. R. W. Murray, the
Sec. II, Ch. 2: The African Diamond Page of 366 Sec. II, Ch. 2: The African Diamond
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