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372
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THE DIAMOND
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of
Dr. Burton suggest that the degree needful depends on conditions. Some
are inclined to think that in the presence of favorable accessories,
pressure only is necessary.
The
Kimberley mines of South Africa lie in a cluster within a radius of a
few miles. These mines, together with others in what was the Orange
Free State and elsewhere, come to the surface in a great plateau
extending from the Transvaal to the Bokkeveldt mountains at the Cape
of Good Hope. The plateau varies in elevation from 2,700 to 6,000 feet
above sea level, being 4,000 feet above, where the four principal mines
are situated at Kimberley.
Until
the discovery of diamonds in Africa, in what is believed to be the
matrix in which they were formed, there were few hints of its origin in
the circumstances of the diamond's lodgment. It was found always in
deposits left by the waters, and the beds in which it lay always showed
the alterations of age and exposure. The gem, unscathed, rested in the
decomposed fragments of the matrix that ages back had bound it. That
the mountains were its original home is evident, for the
diamond-iferous deposits are on high plateaus, on the sides of the
mountains, in the beds of old mountain watercourses, on the hillside
banks and in the beds of the new streams, and sometimes far away in the
plains below, where the mountain torrents have rolled them. And the
crystals hold a record of the long, slow journey. In the mountains,
their corners are sharp and clear, but as they get farther from home,
they become more and more worn and rounded. Up in the hilltops, the big
crystals, wedged in the crevices of the rocks and in the corners
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