There are four basic styles of gem cutting: tumbling, cabbing, faceting and carving. This month’s blog post illustrates tumbling, cabbing and carving. Next month’s blog post will illustrate faceting. Enjoy the reading of this blog post and stay tuned for the next one!
Tumble finishing, also known as tumbling, is a lapidary technique for smoothing and polishing a rough surface. This is the simplest form of gem cutting, where the rough material is put in a revolving barrel with abrasive grit and liquid lubricant. Progressively finer abrasives are used until a polish is obtained. This process closely resembles what happens to rocks in a stream or on the beach, except that the level of polishing is much higher. Jewelry made of or decorated with tumbled semi-precious gems, such as quartzes, are interesting options for a casual yet attractively stylish look.
Cabochons (from the French word “caboche” meaning “head”), which are more commonly known as “cabs”, are gems that are cut with a flat bottom and a curved or domed top. Cutting “en cabochon” is usually applied to opaque gems, while faceting is usually applied to transparent stones. Hardness is also taken into consideration, because softer gemstones with a hardness lower than 7 on the Mohs scale of mineral hardness are easily scratched, mainly by silicon dioxide contained in dust and grit. If these gemstones are polished as cabochons, the scratches will be less evident. Beautiful opals and turquoises are cut into cabochons creating very elegant jewelry pieces.
Carving is a very challenging lapidary art. Gemcutters must have a distinctive artistic sense and a complete understanding of the principles of lapidary. There are several types of carving. Carving a gem in intaglio means that the design is cut into the flat background of the stone. While carving in relief means that the design projects out of the background of the stone. This method is called cameo. Sea shells and agates are often carved with this technique in order to create unique jewelry items.