124 THE DIAMOND MINES OF SOUTH AFRICA
peridot,
jasper, and other richly colored pebbles, lying in and on a bedding of
sand and clay. Below this alluvial soil was in some places a calcareous
tufa, but usually a bed rock of melaphyre or a clayey shale varying in
color. Scattered thickly through the gravel and the clay along the
banks were heavy boulders of basalt and trap which were greatly vexing
in after days to the diamond diggers.1
For
a stretch of a hundred miles above the Mission Station at Pniel the
river flows through a series of rocky ridges, rolling back from either
bank to a tract of grassy, undulating plains. Fancy can scarcely
picture rock heaps more contorted and misshapen. Only prodigious
subterranean forces could have so rent the earth's crust and protruded
jagged dykes of metamor-phic, conglomerate, and amygdaloid rocks,
irregularly traversed by veins of quartz, and heavily sprinkled with
big bare boulders of basalt and trap. Here the old lacustrine
sedimentary formation of the South African high veld north of the
Zwarte Bergen and Witte Bergen ranges has plainly been riven by
volcanic upheaval. The shale and sandstone of the upper and lower Karoo
beds have been washed away down to an igneous rock lying between the
shale and the sandstone. It was along this stretch of the river that
the first considerable deposit of diamonds in South Africa was
uncovered.2
For
more than a year since the discovery of the first diamond there had
been some desultory scratching of the gravel along the Vaal by farmers
and natives in looking for " blink klippe," and a few little rough
diamonds had been found by the Hottentots, as before noted ; but the
first systematic digging and sifting of the ground was begun by a party
of prospectors from Natal at the Mission Station of Hebron. This was
the forerunner of the
1
" Diamonds and Gold of South Africa," Reunert, Cape Town, 1893. "The
Diamond Diggings of South Africa," Pay ton, 1872. "Among the Diamonds,"
1870-1871.
2 " Diamonds and Gold of South Africa," Reunert, 1893. " Among the Diamonds," 1870-1871. "South Africa," Theal, 1888-1893. "On Diamonds," Sir William Crookes, London, 1897.
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