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THE DIAMOND
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yielded
no more. As in West Australia, some of the diamonds, according to Prof.
David, occur in very ancient gravels now consolidated into
conglomerates. The loose gravels are of a much later age.
The
crystals are chiefly octahedrons, though dodecahedrons and similar
forms occur also. They are of various colors, white, yellow, brown,
black, and one twinned crystal of a dark green was discovered.
Diamonds
similar to those of Australia are found in Borneo. They run small, are
very hard and many of them are colored. The fields have undoubtedly
been worked for centuries, as the Dutch on their first arrival there
found mining operations being regularly carried on and ancient native
gems are in the possession of the princes. The rajahs of Panembohan and
Pongerans possess a large belt studded with diamonds, one of them
weighing 67 carats. It is difficult to make a reliable estimate of the
quantity produced. The natives regard the gold and diamonds as a kind
of natural bank provided to be drawn on at pleasure. The native princes
claim all stones over five carats at a fixed price. Undoubtedly they do
not get them all, but naturally there is less public knowledge of the
contraband stones than of those taken by the princes, and of them it is
known only that the overlords have them in their treasuries. As far as
records go, it appears that the production during the first half of
the nineteenth century averaged about 5,000 carats per annum, and it
is thought to be about the same now, though it is probably less, as
mining operations have little encouragement.
In the eighteenth century, the yield was probably much greater, for the fields of Borneo are mentioned, with
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