Cabochon Gems
CABOCHON GEMS
Because cabochons are entirely hand-shaped, the final curved surfaces depend for their geometrical perfection upon the skill of the lapidary. The ideal cabochon should be symmetrical in profile and outline, both of which can be easily determined by visual inspection.
The base of the cabochon should have a slight bevel placed all the way around so that the jeweler will not chip the stone when he sets it into a mounting. The bevel is shown in picture along with some common shaping defects which detract from the quality of cabochon gems.
In mass-production cabochons, especially those from Idar-Oberstein in Germany, and some jadeite from Hong Kong, the form is achieved by grinding on hard-surfaced laps, leaving numerous small flat areas over the surface. Sometimes these are not entirely eliminated by subsequent smoothing operations and appear as vestiges upon the finished stones. These are also counted as defects, and one may be quite sure that their presence signifies an inexpensive material which the lapidary shop did not consider worthy of the additional labor required to make the surfaces truly smooth. On the other hand, more expensive materials, such as fine jadeite, chrysoprase, and catseye chrysoberyl, are treated with great care in respect to shaping and finishing.
A special defect of jadeite cabochons is the development of numerous small shallow pits over the polished surface because of improper polish¬ing techniques. The appearance much resembles the slightly irregular surface of an orange or lemon peel, and, appropriately enough, is known among lapidaries as a “lemon peel” finish. The development of this kind of surface is difficult to avoid due to the nature of the gemstone itself, but the point is, it can be avoided, and when present, lessens the value of the gem.