The stone is then removed from the dop-stick by melting the dop-wax and
is re-dopped to the pavilion facets so that the crown of the stone is
now exposed for cutting. Before the lapidary proceeds with the cutting
of the crown, it is necessary that the stone be perfectly centered on
the dop-stick and that the plane of the table facet be perpendicular to
the dop-stick and to the axis of the arm of the facet head. The eight
main facets are cut first, with numerous adjustments being made by the
lapidary to insure that the proper angle is maintained (fig. 13). Then
the cutting angle is changed a few degrees, the arm of the facet head
rotated slightly, and the crown girdle facets are cut. The crown girdle
facets are placed very similarly to the pavilion girdle facets except
that they are shorter. The crown girdle facets should be joined in
exactly the same way as the pavilion girdle facets. When these facets
are properly cut, the cutting angle is again changed, the arm rotated,
and the eight star facets are cut. This completes the cutting of the
crown of the stone. The cutting lap is removed from the lap plate, and
the polishing lap is secured into place. The facets are carefully
polished in the same order that they were cut. After the last star facet
has been polished, the stone is removed from the dop-stick. Any excess
dop-wax is removed from the stone by means of a solvent, and the full
beauty of the finished gem is revealed.
Tumbled Gems
One other method of finishing gemstones that deserves mention is
tumbling. “Baroque” or “free-form” stones are produced in this manner.
Loose pebbles or pieces of gem materials left over from other cutting
processes are placed in a small barrel or specially constructed box with
loose carborundum grit. The barrel is turned by means of a small motor,
and the abrasion of the pebbles and grit against each other tends to
round the pebbles and give them a finely pitted surface. Progressively
finer and finer carborundum grit is used, and eventually a polishing
compound. The result is several pounds of well-polished gem pebbles of
various shapes and sizes. These baroque stones have found recent favor
in costume jewelry of modern design. The tumbling process is rather
slow, commonly requiring several days or weeks. However, little effort
is involved on the part of the lapidary, and, consequently, the cost of
most tumbled or baroque stones is quite modest. Only gem material that
is unsuitable for cutting in other manners should be finished in this
way.
[Illustration: Fig. 12. Proper placing of the pavilion girdle facets.
Left: facets not joined. Center: facets overlapped, joined too high.
Right: correct placing.]
Stone
Dop-wax
Dop-stick
Chuck
[Illustration: Fig. 13. Proper sequence of cutting of the crown facets.
Left to right: four main facets; all eight main facets; half of the
crown girdle facets; completed crown.]
Public-domain text, read in full here on John Shaqi.
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