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.
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
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.