What makes diamonds stand out beyond any other precious gemstone is their fire and brilliance.

The depth and table percentages, which make a diamond an ideal or good cut, vary from shape to shape. A diamond that is cut too shallow with respect to its width will allow too much light to pass straight through the diamond, leaving little light to reflect. Such a diamond will appear dull and lacking in brilliance. Conversely, a diamond cut too deeply will allow light to escape from the sides of the diamond, also appearing dull.

All the facets should be highly polished and correctly shaped. A poorly polished diamond lacks brilliance. Proportion problems are often seen in diamonds graded as Fair or Poor; they can include severe misalignment of facets, a noticeably off-centre table, a noticeably 'wavy' girdle, or a table which is noticeably not parallel to the girdle.

In order to cut a stone to ideal proportions, much of the rough diamond is sacrificed, leaving a stone with a smaller carat weight. Diamond cutters sometimes sacrifice ideal proportions to end up with a larger, more profitable stone.

Consequently, ideal cut stones are very rare and hard for wholesalers and retailers to find, and as the consumer, you will see that retail jewellery stores price accordingly.

To obtain a diamond that has the most brilliance then choose a cut grade of ideal or very good and proportions of ideal or excellent.
For value for money, choose an ideal or very good cut with proportions of ideal or excellent. You might then consider less expensive grades of colour, such as G-H and a clarity grade of SI1 - SI2.