The Bead was probably the first gemstone cut used by man, dating back several thousand years. Limited by the tools available at the time, as well as the hardness of most gemstones, the simple bead or 'cabochon' were the logical choice for jewelry making and ornamentation. Stones where shaped by rubbing them with other stones, then polished using 'sand' as an abrasive.
Intricately carved cabochon cuts known as 'Glyptic' gem carvings, date back to the 7th millennium BC, and were popularized throughout ancient Egypt (scarabs), Indus Valley, and China (carved jade).
Engraved 'Glyptic' gems were used as personal signets or seal-stones which could be impressed into wax or clay to create a signature. The examples above are of early Roman gemstone cuts using the pre-renaissance cabochon cut with several variations of cameo and intaglio styles.
Medieval Lapidary Techniques
A "lapidary" (edelsteinschneider) is an artisan who works with stone, minerals, or gemstones, forming them into decorative or functional objects. The term "lapidary" is derived from the word lapidaries, which were medieval 'treatises' on alchemy, mineralogy, chemistry and other sciences.
Perhaps the best documentarian on the subject of medieval gem-cutting was Theophilus Presbyter (c.1070 - 1125), a Benedictine monk with a fascination for the applied arts. In Theophilus' 'On Divers Arts' De diversibus artibus (c.1125), his treatises on the polishing of gemstones goes into great detail in describing various techniques. For the polishing of "onyx, beryl, smaragdus (emerald), jasper, chalcedony, and the other precious stones" you would make a very fine powder from "fragments of crystal" or "emery" and then work the stone on a "smooth flat limewood board, wet with saliva."
Theophilus also describes the method for using a 'dop stick' by attaching the gemstone to a "long piece of wood of comparable thickness" using "chaser's pitch," then rubbing the stone on a wet "piece of hard sandstone," and decreasing the grit of the abrasive until the stone "becomes brilliant." Then, using "tile dust moistened with saliva on a goat skin," you would rub the stone until it is "completely clear."
To create intricately carved cabochons, cameos, and intaglios (photo above) out of sapphire, early Roman engravers may have used 'adamas' (diamond) fragments as carving tools, given that they are the only material that is harder than corundum.
The Cabochon
A cabochon (cabouchon) is a gemstone which has been rubbed and polished into a simple rounded shape, as opposed to a facetted cut. Up until the 1400s, gem cutters were constrained to cabochon style cuts and odd asymmetrically faceted cuts due to the limited technology at hand. The resulting shape has a convex top with a flat or concave back. The term cabochon is used to describe any gemstone cut shape that is not facetted.
When a gemstone is cut en cabochon, the miniscule amount of light that is able to enter, and exit through the stone is due primarily to its crystalline structure and optical properties, and has little to do with the gem-cutter's expertise.
Today, cutting a stone "en cabochon" is usually applicable to opaque gems, although transparent semi-precious gemstones are also cut as cabochons. Variants of the cabochon include the cameo and intaglio cuts shown below.
