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Cabochon Cuts

From Gem Cutting, A Lapidary's Manual by John Sinkankas

Before proceeding with the actual cutting of a cabochon, you must have clearly in mind the use to which the finished stone will be put. Is it going to be used in jewelry; if so, what kind? Or, if intended as a part of a collection, are the factors of shape and size important? The answers to these questions may easily give an exact purpose to your cutting and very likely lead to more worthwhile results.

Selecting a Style of Cut

The variations in shape of cabochons are virtually limitless; but, in general, only a few standard shapes are cut. These are: the oval (really an ellipse), the circle, the angular or polygonal shape, the heart, the pendant, and sometimes the cross. Hearts and crosses are always attractive but are difficult to do well. Irregular shapes are currently popular, both in thin slabs possessing a striking pattern and in the so-called "baroque" gems. The latter are merely small pieces of rough, smoothed and polished all over without any attempt to make the shape regular. Their deliberate lack of symmetry is pleasing in a barbaric way.

The selection of a cabochon shape must be also governed by practical considerations. The long, narrow, navette shape, for example, is intriguing, but if meant to be put in a ring, it will present some serious problems. Not only is it more difficult to make, but its sharply pointed ends are apt to catch on clothing and result in bending or breaking the ring. Cabochons cut in large sizes are seldom practical for brooches unless the cutter makes them thin in cross section to reduce weight. If too heavy, they will tend to hang improperly from the clothing. Because of this consideration, commercial cutters have learned to cut such stones into thin sections, sometimes even hollowed out on the back, and always with the view that expensive gem material can be more economically used in thinner slices. Earrings of the screw type can be the most troublesome of ll jewelry and the most easily lost if they are extremely heavy. For safety, such earrings must be screwed on too tight for comfort. Bracelet stones also cannot be too large, but for a different reason. If meant to be set in a series of links, they should be small enough to allow the assembled bracelet to curve smoothly and gracefu11y around the wrist.

Many amateurs do not cut cabochons for jewelry purposes but rather as items for their collection. In such a case the use of "standard" sizes is not required except for the sake of consistency. However, if the stones are to be mounted in ready-made mounts, accurate cutting is necessary. Exceptionally good material should be cut on its own merits, probably deserving a fine, handmade mount anyway.

The beginner's work is most often revealed by the excessively heavy tops he puts on his first stones, a practice seldom followed by the professional. There are times, however, when thick tops are needed, either for an appropriate effect, or for safety's sake in the case of materials that are fragile or easily split. Amazonite, the lovely green feldspar, for example, possesses several easy cleavages and, unless cut fairly thickly, may break apart during cutting. Certain transparent and translucent gems, such as amethyst and rose quartz, may, in thin sections, present a washed-out appearance. Obviously, the intensity of the color will determine largely how thick such gems should be cut.

Cabochon shapes are not only classified as to outline but to cross section as well. The most common section is that in which the bottom is perfectly flat and only the top is curved. Starting from sawed slabs, this shape is easiest to attain and is also most satisfactory for setting in jewelry. If both top and bottom are rounded - the top usually more so - he cabochon is known as a "double-cabochon." This shape, if thin, is also called a "lentil" in allusion to its bean-shaped cross section. Seldom encountered and difficult to accomplish is the hollow cabochon, used to give lightness of weight and color. In this type, the back of the stone is ground away with sphere-shaped metal cutters charged with loose grit and then polished. It is almost exclusively used for dark-red almandine garnets or "carbuncles." Without such hollowing out, many almandines would appear as black as coal. A simple yet highly satisfactory cross section for large stones is presented by thin, flat slabs carefully polished on both sides and the edges neatly finished in single or double bevels. This mode of preparation is well suited to pendants and brooches.

The upper upper curvature of cabochons may be further classified as to the steepness of the curve. A shallow curve is called a "low" cab; then there are, successively, "medium" and "high" cabs. Each has a particular application.