Attitudes toward cabochon-cut gemstones vary from country to country. The United States and Britain view faceted stones as the more desirable form of gem and attach much less value to cabochons. Germany, on the other hand, has a strong tradition of producing fine, well-cut cabochons, and jewelry buyers appreciate the qualities of colour, texture and light.
The choice of material in cabochon form is much wider and cheaper, and it is a less dominant form that offers greater flexibility in design. It is not really surprising, therefore, that contemporary jewelry designers elect to use cabochons more often than faceted stones. Many crystal types are too brittle or the rough too flawed to facet but they remain a wonderful source of material for cabachon stones.
Usage and common faults
The majority of gemstone types, from ruby and emerald to agate and quartz, can be found in cabochon form, including material that is too soft to be faceted, such as amber, apatite, rhodochrosite and fluorite. Low grade material has traditionally been used for cabochons, but the quality is now improving. Obviously, the best gem material will still be kept for faceted stones.
Stars and cat’s-eyes are always cabochon cut, as are the majority of stones with interesting optical effects, such as opals and moonstones. The gem material has to be oriented correctly and the cut itself will affect the quality of the effect – a low buff top will display better iridescence and schiller than a high domed cut.
The most common problems with cabochons are cracks and surface abrasions, flaws that are too close to the surface (which are unsightly and might cause the stone to break), poor finish and polish, lack of symmetry and muddy or dark colour. Check that the slope from the base of the cabochon is sufficient for the stone to be bezel-set or mounted. If it slopes too sharply there is a risk of the girdle chipping while it is being set, and the stone may not be gripped securely by the setting.
High, elongated bullets need to be set with care as the top of the stone can snap under pressure. Check a hollowed out carbuncle for any cracks or major flaws that could make it fragile, Carbuncles are often backed with a foil reflector to increase brilliance.
Range of cuts
Cabochon cuts can vary in both outer girdle shape and the convex curve of the surface. The shapes – such as the marquise, pear shape and cushion – are the same as those of faceted stones and they are cut in the same calibrated sizes, but the weights are different. The surface profile can range from a flat slab to a high-domed bullet. The base can be flat, or rounded as a double cabochon to increase colour density in lightly coloured transparent stones. Cushion cuts are always popular; they can either have a plain, smooth dome or be cross-vaulted, with ridges that intersect on the diagonal.