Gem carving and engraving has been performed since ancient times – jade has been carved decoratively in China for the last 3,000 years. Today, the main producers of gem carvings are India, China, Hong Kong, Thailand, Italy and Germany.
The carving of gemstones has traditionally focused on cameo and intaglio work, although it is also possible to find decorative designer work. The lapidaries of Germany have a strong tradition of carving. Their work is very fine, using high-grade material, but the pieces are rather expensive. Carvings from the Far East are cheaper due to lower labour costs, and much more traditional in design.
The carving of freeform gemstones is currently practised by a relatively small number of lapidaries and jewellers. Large-scale work requires machinery such as flat laps, drum sanders, diamond grinding wheels and polishing machines, which can be expensive. It is possible, however, to carve on a small scale, using silicon carbide and diamond drill bits and burrs in conjunction with a flex-shaft hand piece and power rotary tool. The diamond polishing compounds can be used on felt buffing wheels and mops.
Choosing the right materials
Carving material should ideally have a tightly knit granular structure, as found in jade, agate and chalcedony. If the material is crystalline, it should be tough, free of internal stresses and easy to polish, like heliodor (beryl). The material’s hardness and cleavage will affect the polishing of a stone – polishing on a cleavage plane is very difficult because portions of the crystal will be lifted as you work. Other important factors are the material’s fracture, porosity and ability to cope with heat and chemicals.
Pleochroism has to be considered as it will dictate how the material is oriented. You also need to assess the number, type, position and colour of any inclusions, as well as colour distribution and zoning. Furthermore, if a gemstone has been treated by staining, stabilizing or fracture filling, it could lose colour or crumble when being carved.
- Keep the gemstone material wet to avoid overheating it. Don’t push too hard or for too long with the rotary tool drill bits and don’t let them dry out. Heat can affect the colour and clarity of the stone, or cause breakage.
- Don’t skip the polishing process. Taking time to gradually “step down” in the grits and grades of diamond pads or paste will make a superior finish.
- Joints should be glued with a good-quality synthetic epoxy resin. This will retain a small degree of flexibility that instant adhesives don’t possess – superglues can become brittle with age and the bond will eventually break. Work with the epoxy resin while it can be applied thinly and sparingly. Remove excess with a scalpel.