Cutting Gemstones

Diamonds and other precious gems are well known for their use in jewelry, but naturally-occurring gems do not come in the classical shapes that people recognize in a ring, brooch or necklace. All gems must be 'cut' in order to produce the nice facets that reflect light multiple times as it passes through the gem and gives rise to the sparkling nature of gemstones. The cutting process is actually one of careful cleavage and grinding of the crystal faces uses an abbrasive fine diamond grit. Those who cut gemstones are called by two different names. The first is lapidary gem cutters and diamond cutters. All gemstones are not cut in the same ways because the crystal lattice planes running through the stone will split or grind down more easily in some directions than others, depending on how strong the bonding is that holds those planes to their neighbors. These are known as cleavage planes and they are different for minerals with different crystal systems. Diamond has its optimal planes for cleavage along the faces of an octahedron. Some of the typical cuts for diamonds are illustrated for the various fragments of the Cullinan diamond, the largest clear diamond ever found, weighing over 3000 carats or approximately 1 lb 6 oz. The diamond was cut into 105 smaller pieces and the largest two are found in the Sovereign's Sceptre with Cross and the Imperial State Crown, part of the Crown Jewels of the United Kingdom.