Gemstone crystals often have naturally brilliant, reflecting faces, but rarely are they perfect and unblemished. Also, their natural shapes do not provide the best expression of their luster, brilliance, dispersion, color, and other inherent properties. In fashioning a gemstone, the skilled artisan tries to develop these hidden assets and to otherwise enhance the gemstone’s general beauty.
From ancient times until the 1600’s little was attempted in the way of shaping gemstones other than to smooth or polish the natural form. Although similarly smoothed, or tumbled, gemstones recently have returned to fashion, the finest pieces of gem rough are now converted mainly into faceted, or shaped, stones. Standard types of facets—the flat faces that are ground and polished on the rough gem material—have been given individual and group names. A typical example is the brilliant cut, which is most commonly used to best bring out the qualities of a diamond.
The standard brilliant cut, with a pattern of many facets, is commonly used for gemstones having a high refractive index and, therefore, great brilliance.
Characteristic of the standard brilliant cut are the 32 crown facets surrounding a relatively small, flat, table facet and the 24 pavilion facets and culet at the bottom of the stone.
Ideal proportions for the standard brilliant cut have been carefully determined so that the maximum amount of light will be reflected back out the top of the stone. Incorrect proportions cause the light to be lost at the bottom of the stone.
The step cut, often called the emerald cut, frequently is used for colored stones because the large table permits a good view of the color.