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Borneo Diamonds.
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At
all these localities the Diamonds are found with gold and, in some
cases, with platinum, in the sands of the rivers; and also in beds of
clay, sand and gravel, sometimes at a considerable depth. A blue or
bluish-grey Corundum, known as Batu timahan, is said to be a
constant companion of the Diamond, the natives regarding it as an
attendant on the "Prince," as they term the more precious stone. Dr.
Verbeek thinks that the original matrix of the Diamond, which yielded
the stones occurring in the drifts, is to be found among the older
slaty and schistose rocks ; whilst the late Prof. Carvill Lewis
suggested that the Diamonds had been brought up from depths by the
serpentine, or altered peridotite, which appears to be not uncommon in
the Diamond districts of Borneo.
The
natives wash the sands of the rivers in small bowls, and become so
expert in detecting the valuable stones that they can separate the
Diamonds from the worthless minerals, even when so small as to escape
observation by Europeans. The drifts are worked by means of small
shafts sunk through the overlying deposits, and the Diamond-yielding
bed is then followed by little tunnels driven in a very primitive
manner. Considerable improvements have, however, been introduced by the
Chinese, who are extremely skilful and economical miners. Of late years
Europeans have entered the field, and Diamond-mines in Tjempaka are now
worked by French engineers ; but the washing of the Diamond-earth after
its extraction is said to be still done on the old Malay system.
The
Diamonds of Borneo usually occur in crystals, presenting the form of
the octahedron, the cube and the rhombic dodecahedron. If they present
bright faces and sharp angles, and are considered by the natives tó
need no
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