which
the grain and how to polish that particular facet is known. The work is
done on flat, horizontal wheels which make about two thousand
revolutions a minute.
During the polishing or grinding the diamond is kept moist with a mixture of olive oil and diamond-dust.
Ideal
cutting not only requires exact proportions, but the placing of the
facets mathematically true. The culet should be opposite the centre of
the table, and their eight sides parallel to each other; the edges of
the top and bottom corner facets should correspond, and the dimensions
of their bases be alike. The edge of the stone should be cut evenly.
Some prefer the finished appearance of a polished knife edge, though
there are those who think it better to leave a very thin line of the
skin of the stone around the edge, as it is less liable to chip and
split. The skin being harder, it protects the natural cleavage along
the grain of the stone. Nor is this detrimental to the brilliancy if
the proportions are right. If, on looking into a stone, reflections of
the edge appear in the body, its proportions are not exact.
It
is impossible, however, at the general market price of the various
qualities, to supply stones of absolutely perfect cut. The waste and
care necessary to produce them add materially to the cost;
nevertheless the public are rapidly learning the value of this kind of
work, and as they become convinced that the increase of cost is
returned to them in a full increase of value, they willingly pay the
difference. It takes time to fully appreciate a perfectly cut stone,
but acquaintanceship adds to the pleasure of its possessor and to his
confidence in the dealer who sold it to him.
Another
form of cutting diamonds, confined usually to small stones, and by
which pieces too small for brilliants are utilized, is the " rose." It
is circular, quite flat below, and rises to a low pyramid, which is
covered with facets. Figs. 4 and 5, Plate XIV., give a side and front
view of the " Dutch" rose of twenty-four facets. Fig. 6 is the "
Brabant"
5
