1900s

In the early 1900's, the development of diamond saws and jewelry lathes enabled the development of modern diamond cuts, including the Round Brilliant cut. The modern Round Brilliant consists of 58 facets - 57 if the culet is excluded. There are 33 on the crown and 25 on the pavilion. In recent decades, most girdles are faceted. Many girdles have 32, 64, 80, or 96 facets.

On June 25 1905 the largest rough gem-quality diamond in the world was found by Frederick Wells, of the Premier Diamond Mining Company in Cullinan, Gauteng Province, South Africa. Called the "Cullinan Diamond" it weighed 3,106.75 carats or 621.35 grams. The largest polished gem cut from the stone is named the "Great Star of Africa" (above, right) and was 530.2 carats.

Even with modern techniques, the cutting and polishing of a diamonds resulted in a loss of as much as 50% of the stone's total weight. The round brilliant cut is preferred when the crystal is an octahedron, as two stones could be cut from one crystal. Asymmetrical crystals such as macles are usually cut in a "Fancy" style.