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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
African Diamonds.
87
the rocks, and so force open the channels which we recognize as the "pipes." The vapour rushing up these pipes might tear the shales and other rocks forming the walls, and thus give rise to fragmentary materials to be caught in the uprising pasty magma, producing as it cooled a brecciated mass. The pipes have thus become filled with a medley of materials, partly brought up from great depths, and partly due to the disintegration of the local rocks. But the Diamonds which give supreme value to the breccia have been formed in a deep-seated laboratory under the pipes, where carbon has crystallized from a saturated bath of iron, under prodigious pressure, and with inconceivable slowness.
In the early days of Diamond-mining in South Africa, the ground in these volcanic necks was worked as quarries, or open casts, and the material was hauled up by means of aerial wire ropes. Much inconvenience however was experienced as the diggings grew deeper, especially by the heavy falls of the surrounding shales, or "reef," which tended to slip in large masses into the workings. More­over, the shales contained iron-pyrites, which occasionally ignited spontaneously, with disastrous results.
An entirely different system of working was therefore introduced at the Kimberley Mine, and this was soon followed at De Beers. Shafts were sunk at a convenient distance from the pipes, and successive galleries driven into the Diamond-bearing ground, as in the ordinary system of underground mining. The rock is brought down by drilling and blasting, and is run in trucks to the bottom of the shaft, up which it is hoisted in skips running on steel rails and worked by a steam winding-engine. The mines are fitted with all modern improvements, such as electric lamps and telephones connecting the different centres of work.
Sec. II, Ch. 2: The African Diamond Page of 366 Sec. II, Ch. 2: The African Diamond
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