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48
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GEMS.
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uncut
diamonds; most frequently it is of a greyish white, and cannot acquire
the diversified colours of the pure diamond, which it however exceeds
in specific gravity; With us, it is only used to polish the reguÂlarly
crystallized diamond ; and for this purpose it is pounded in a mortar,
and its dust, mixed with oil, and spread over a surface of soft iron,
renders the friction of the two diamonds more efficacious, and thus
assists in obtaining the polish and splendour of the different facets.
It
is known that, whatever the variations of certain crystals, it is easy
by means of their cleavage to reduce them to a regular determined form
; but in the knotty diamond this is impossible, as its texture does not
permit of cleavage.
The knotty diamond is found in the mines of Brazil, whence they are sent to Europe.
Some
people say that the boost is cut and used by the Orientals ; but, even
if this be so, they certainly have not in it a bright or valuable gem.
XVII.
CACHOLONG.
A barbarous name, not yet translated into any EuÂropean language, and originating in Bokhara, from the words of its dialect, each, river, chölong, stone ; that is, " stone of the river." It belongs to the variety of the opal chalcedony ; opaque on the surface and of a milky
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