Gemmology | Introduction | Cut in gemstones

Commercial cut in sillimanite — specimen 0113, photo © NMNHS

Precision cut in grossular (tsavorite) — specimen 0094, photo © NMNHS

The cut in gemstones is also of great importance. Generally there are two types of cuts — commercial and precision. The main objective in first one is to preserve as much as possible of the crystal’s size, respectively weight, while the second follows exact proportions, angles, etc., always in relation with the specific mineral.

During the cutting process the gemstone is given a different form, which may be with curved surface, as in cabochon type, or consisting of facets. Huge database of various faceting diagrams exists on FacetDiagrams.org.

Diagram of standard round brilliant, showing the main elements of a faceted stone — the upper part is called crown; the bottom — pavilion; the small belt separating the two parts is called girdle; the wide flat facet in the middle of the crown is table; the bottom end of the pavilion — culet

Cut can be brilliant, step, mixed or otherwise. Some of the most popular shapes include round, oval, cushion, cushion triangle, octagon, pear.