Early gem cutting and fashioning usually worked with the shape of the rough material, that is a stream worn pebble would simply be polished. Carved jade has been found with Chinese burial sites dating from 3000 BC (Hurlbut and Kammerling, 1991, p. 181). Cylinder seals were used as signatures and beetle-shaped scarabs were common in ancient Egypt. Advanced machinery and techniques would eventually give rise to improved cabochon cuts and faceting, which is more dependent upon the physical and optical properties of gem rather than the shape.

Photo date 10/99 © by S.W. Aber

The purpose of cutting a gemstone is to maximize the beauty. In general, transparent gemstones are faceted to enhance interaction with light, thus improving the brilliance (amount of light reflected), scintillation (sparkle and flashes), and fire (spectral colors). This light interaction enhancement is through reflection, refraction, and selective absorption.

Photo date 10/99; © by S.W. Aber

Translucent or opaque gemstones are cut en cabochon or carved, maximizing the surface reflection of light and displaying unique color banding or patterns in the gem. A desirable optical effect can also determine the cutting style (e.g., asterism and the chatoyant cat's-eye require cabochon cuts).

Photo date 10/99; © by S.W. Aber

Photo date 10/99; © by S.W. Aber

Faceting began in the fourteenth century, with the earliest fashioning simply to polish natural crystal faces (Hurlbut and Kammerling, 1991, p. 183). Faceting is almost exclusively applied to transparent gemstones because this type of cutting maximizes reflection and refraction, and therefore the gemstone's brilliance, scintillation, and fire. If the gem is correctly cut, then light that passes into the gem will strike the back facets, be reflected twice, and then return to the eye, that is if it hits at an angle that is greater than the critical angle. If the gem is not cut properly, the light entering the gem will be refracted out the bottom of the gem, or it "leaks" out from the stone, i.e. when light lands within the critical angle. The larger the gem's refractive index the smaller the critical angle; the smaller the critical angle, the shallower the stone can be fashioned and still maintain brillancy (Hurlbut and Kammerling, 1991, p. 183).

The faceted gemstones consist of three main parts, the crown, girdle, and pavilion. The crown is made up of a table (large facet at the top of the stone), upper main facets (8, kite shaped), star facets (8, triangular), and upper girdle facets (16, triangular). The girdle (also known as the setting edge) is the section between the top and bottom of the stone and defines the perimeter, thus the overall shape of the gem. The pavilion has lower girdle facets (16, triangular), lower main facets (8, kite shaped), and the culet (small facet where the pavilion facets meet at a point). The eight lower main facets actually create an octagon shape to the culet. There are two basic faceted cuts, the brilliant and step. The emerald cut and round brilliant are the basis from which most other cuts are based. A mixed cut would consist of, for example, a brilliant cut crown and step cut pavilion. Although new cuts are introduced fairly often, in 1988 DeBeers introduced new cuts specifically designed for misshapen or colored diamonds, called the sunflower, dahlia, marigold, zinnia, and fire rose.

Jack Greer explaining the different facets. Photo date 10/99; © by S.W. Aber

A cut developed prior to the sixteenth century was the rose cut or rosette. It has a faceted crown and no pavilion. This cut was popular for diamonds and garnets in Victorian jewelry (Hurlbut and Kammerling, 1991, p. 185). The table cut was another early cut which took advantage of the octahedral shape of many diamond rough, simply creating four facets on the crown with a table and four facets on the pavilion with a small culet.

The step cuts have rows of facets that resemble a stairway. The outline, or perimeter which is shown by the girdle, may be rectangular, square, triangular, kite shaped, among others. Long rectangular step-cut gems are known as baguettes, often used as side stones in a setting, while rectangular shaped and cut-corner or faceted corners is known as the emerald cut, often used with emeralds.

Brilliant cut gems have crown and pavilion facets, kite or triangular shaped, that radiate out from the center. The outline may be round, pear, oval, marquise, and more. The old mine and old European cuts were forerunners to the round brilliant. The cut was similar to the round brilliant, except for a squarish outline (old mine) and higher crown, smaller table, and large culet. The round brilliant cut is often used for diamonds, believed to be first utilized at the end of the seventeenth century (Hurlbut and Kammerling, 1991, p. 186). Cuts that vary from round though, have pavilion facets that do not line up at the proper angle, which results in light leaking out the bottom of the stone and a bow-tie effect. This darkened area in the shape of a bow tie reduces the brilliance.