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.]