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142 THE DIAMOND MINES OF SOUTH AFRICA
from
concave wooden plates with a peculiar whirl which hastened the
separation of the heavier gravel. This concentrate, containing most of
the diamonds in the cascalho, was then washed again in a batea, a
wooden dish with a depression in the centre. By dexterous shaking and
whirling motions of the batea filled with water and a few handfuls of
gravel, the lighter gravel
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was carried to the rim and washed or scraped away, and
diamonds mixed with heavier pebbles were collected in the hollowed
centre of the dish. A gentle tilt of the batea drained off the water,
and the precious stones were picked from the other pebbles by hand.
Sometimes
the formacao was deposited in an inclined movable trough or cradle on
whose face fifteen to eighteen pounds were spread out at a time. Then a
carefully regulated stream of water was allowed to run through this
deposit into a lower trough and gutter while the cradle was rocked
continually. When the water ran off clear from the lower trough, the
working negro would pick out the stones in the cradle with his
fingers, until only the finest pebbles remained, which he scraped over
and examined with the closest attention to detect the possible
presence of diamond crystals.1
1 "A Treatise on Gems," Feuchtwanger, 1867. Report of United States Minister to Brazil, March, 1 899.
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