In 1919, M. Tolkowsky, physician and mathematician, published a study on the optical properties of the round brilliant cut. He suggested angles, optimal proportions. These (updated) values are nowadays referred to as the cut grade, noted in certificates. It is the first variable parameter which will determine the beauty transmitted through the fixed data (clarity, colour), and nowadays people tend to attach great importance to it.

In most certificates (HRD, IGI, GIA…), the qualifications are summarised by easily understandable generic terms (such as “very good”, “good”,…).

The diamond is a light accumulator. When a diamond is cut according to good proportions, qualified as cut grade, the light remains imprisoned and reflects itself from one facet to the next, exploiting the diamond’s refraction property to the maximum, and it then comes out again through the top (the table). A diamond that deviates from the ideal proportions lets part of the light escape through its table.

The proportions defined by the cut grade determine the fire and the brightness (light return), the scintillation of the diamond. It is the most important criteria. The finish grade qualifies the divergences in the symmetry of the cut shape, the facets and the quality of the polish.

These criteria are often ignored. We attach the greatest importance to them: all our diamonds are exclusively “excellent”, “very good” or “good”. Diamonds of a “medium” or “bad” quality convey the choice of favouring weight instead of the quality of the cut.

The girdle is the circumference of the diamond, which will be used to fix the diamond in the jewel. The thickness of the girdle enters the qualification of the proportions (avoid girdles described as “very thin” or “very thick”). The exterior aspect of the girdle (polished or facetted) does not enter the qualification. You often find what are known as “natural facets” in the girdle, they are proof of the original rough stone.

Proportions of cuts known as “fancy shapes” ex. the Princess cut
There are no established or generally accepted rules, but take note, however, of the following criteria and how they differ from the brilliant round cut:

• the larger table, generally 65% to 75% more, and you find beautiful princesses with tables of 80%;
• many princesses have a feeble height of the crown, of about 11% or just below;
• the pavilion, deeper, around 60 to 64%;
• the girdle, always polished, from 2,5 to 5% if not more, since the thickness does not diminish the light return. As there are tips (the angles), a girdle that is a little thicker represents a guarantee of solidity.

For more information about diamonds please contact-us.