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Faceted Gems

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

A faceted gem can be most easily described as one which the outside is covered with a series of flat, polished surfaces called facets. In this respect it differs from a cabochon where the primary feature which captures our notice is the smooth and unbroken curvature. Customarily, faceted stones are cut from transparent material to take advantage of the additional brilliancy which this mode of fashioning provides. Yet, depending upon the tastes of the cutter, much opaque material is also faceted, the twinkling geometric reflections cast from the surface being considered a more attractive way of displaying the beauty of the stone than the rounded shape of the cabochon. Dead black gemstones are often cut in facet style - for example, tourmaline, spinel, black diamond, jet, and hematite. Even the lowly agate is often cut in faceted beads. There is no hard and fast rule governing which stones should be faceted, it being primarily a matter of taste; but it must be noted that transparent stones gain most by being cut in this fashion.

Brilliancy in gemstones is due to the reflection of light from the surface of the gem, and in the case of transparent stones, reflection from within also. The two intermingled reflections, which shift and sparkle as the stone is turned, depend for their intensity upon optical properties of the particular gemstone and the methods employed in its shaping and finish.

Styles of Facet Cuts

There are two basic styles of cutting faceted stones from which all other cuts are derived, the brilliant cut and the emerald or step cut. As shown in the diagram, the chief difference between the two is in the shape of the facets and their placement about the gem. In the brilliant cut, the facets are triangular or kite-shaped while in the step cut, all facets are more or less rectangular and arranged in parallel or in "steps."

The brilliant cut is particularly suited for, but not confined to, colorless or faintly colored stones which, lacking hue, must depend on clean, sharp, brilliant flashes of light for attractiveness. Step cuts may also be used for pale or colorless stones but find their greatest employment in stones of a decided color. There, again, no hard-and-fast rule governs the selection of a style, and the taste of the cutter, as well economic considerations, will determine which one will be selected. Today's taste in gemstones is toward the simple perfection of the step cut for almost all colored stones and even for those only faintly tinged.