The most important of the 4C's is the cut of a diamond. Most consumers believe that cut refers to the shape of the diamond, which it does. However, a more important aspect often overlooked by retail stores is the geometry and proportions of the facets.
In an ideally cut diamond, the geometry and proportions of the facets are such that light entering through the table of a diamond travels to the pavilion of the diamond and is reflected to the other side before being reflected back out of the table of the diamond.
In a poorly cut diamond, i.e. one that has been cut too deep or too shallow, the light is not reflected back off the pavilion, but instead is lost through the sides and bottom of the diamond, leading to less brilliance and correspondingly less value. Unfortunately, some diamond cutters and polishers will sacrifice the geometric quality of a cut to maximise its size. Jewellery Connection recommends only purchasing diamonds that are graded as "Excellent" or "Very good" cuts by an independent grading laboratory.
- Round brilliant cut: The most popular style of diamond cut. This diamond has 57 or 58 facets.
- Emerald cut: Rectangular or square step cut with diagonally cut corners and two, three, or four rows of facets parallel to the girdle on the crown and pavilion. It is frequently used to fashion emeralds. If the shape is square, it is called a square emerald cut.
- Pear: Variation of the brilliant cut with a pear-shaped girdle outline and 56 to 58 facets. Also called pendeloque or teardrop.
- Princess: popular square or rectangular modified brilliant cut usually with 57 facets (21 crown facets, 32 pavilion facets, and four girdle facets) but occasionally a rectangular or square brilliant with 144 facets. Many variations are on the market
- Marquise: Elongated, boat-shaped brilliant cut with curving sides and pointed ends, developed in France in the 1740s. Believed to have been named after the Marquise de Pompadour, a mistress of King Louis XV. Also called navette.
- Heart: Modified brilliant cut in the shape of a heart, with a table, 32 crown facets, 24 pavilion facets, and a shield-shaped culet.
- Oval: Brilliant cut with an elliptical girdle outline ; also called an oval brilliant cut. Obsolete barrel-shaped cut, circular in section and covered with triangular facets.
For more information on the 4C's Clarity - Carat - Colour