What Is a Cabochon? How this Jewelry Component is Made and Used
The shape cabochon (KAB-oh-shon) refers to a piece of gemstone (or other material) which has been shaped and polished, instead of faceted. Such stones have a domed front surface and a flat back.
The process of creating this shape is called cutting en cabochon, and is usually applied to softer gemstone materials, opaque gemstones and stones which display special effects such as asterism (displaying a star across the surface), chatoyancy (sha-TOY-en-see--a cat's eye effect) and iridescence (a play of colors within the stone). Popular materials to cut en cabochon include star ruby, star sapphire, amber, jade, opal, Oregon sunstone and rainbow moonstone. The most common shape is an oval or ellipse, although other geometric and freeform shapes are also cut.
How to Cut Cabochons
Cabochons are usually cut from a slice of gemstone rough or other materials using a calibrated stencil template, or in freeform shapes for customized manufacturing. Due to labor costs, cabochon making frequently begins on a cam-cutter, a machine that completes 75% of the cutting process. Individual cabochons are then ground into shape with grinding disks or belts coated with silicon carbide or diamond dust. Cutting cabochons can be an expensive interest to get started with, even on a hobbyist level. It's how Stuart got started in the business, so we can say that from experience!
Cabochon stones (often shortened to "cabs" in the jewelry-making world) are shaped using a handcrafting technique called dopping (pronunciation: DAHP-ping). Dopping involves adhering the cab to a dowel or rod with a hard wax, creating the curved or beveled edges, then sanding and polishing the top into a uniform dome. As most of this work is done by hand, the height and curve of the dome varies, which can affect how the cabochon fits in standardized settings.
Cabochons are calibrated to match popular or frequently used standardized setting sizes such as 20mm round or 40x30mm oval. Calibration refers only to this size-and-shape indicator. Cabochon qualities such as gemstone grades, polishes, finishes, beveled edges or carved surfaces are not affected by whether a cabochon is considered calibrated or uncalibrated.
Calibrated cabochons can still vary greatly, even if they fit the measurement and shape guidelines. Cabochons are measured by their largest points: side to side and end to end. The arc or curve between those compass points can be shallow or deep, resulting in cabochons which are calibrated yet not identical in shape. Oval cabochons are the most variable, as they can vary between a narrow curve close to a marquise to a wide curve similar to a rounded rectangle.
Cabochons are rarely the same because of dopping and the range of Mohs hardnesses in cabochon materials making some stones difficult to cut and polish--plus wear-and-tear on lapidary machinery. These factors contribute to varying calibrations from cabochon to cabochon.
Cabochons can be used in calibrated settings, designer-created bezel settings and other artistic techniques.
Calibrated cabochon settings include Cab-Tite™, Wrap-Tite®, Bezellite, cinch mount and Almost Instant Jewelry® settings, as well as most solid-back and open-back bezel cups, prong-set and glue-in settings. Settings include pendants, drops, links, rings, bracelets and a variety of earring findings.
As the arc or curve of a cabochon's shape--as well as the height of its dome--can vary, jewelry designers may need to take extra care when selecting settings or mountings. Settings made of rigid metals such as brass and pewter may not fit all cabochons, even if both mounting and cabochon match in millimeter sizes. This is especially true of oval settings, as the curve of the oval in setting and cabochon may not be identical, as you can see below. Each cabochon is an oval measuring 40x30mm, yet jewelry makers can see how different each cabochon is compared to the others.
Custom settings can be created for uncalibrated or freeform cabochons using bezel strips and metal sheet, or a range of metal clays: BRONZclay™, COPPRclay™, Art Clay® and PMC®.
Designer-artists can showcase non-calibrated cabochons in standard shapes--oval, round, marquise, teardrop and others--as well as freeform cabochons by adhering them to flat surfaces (such as Aanraku® bails), freeform wire-wrapping around them, wirewrap them using the cabochon mandrel, embedding in soft media such as polymer clays and Apoxie® Sculpt or embroidering onto backing materials using seed beads.
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