Diamond Cut

In 1919, M. Tolkowsky, physician and mathematician, published a study on the optical properties of the round brilliant diamond cut. He suggested angles, optimal proportions. These (updated) values are nowadays referred to as the diamond 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.

Cut Grade
 

EX excellent | VG very good
G good | F fair | P poor

Polish Grade

EX excellent | VG very good
G good | F fair | P poor

Symmetry Grade

EX excellent | VG very good
G good | F fair | P poor

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 diamond 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 diamond 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.

There are no established or generally accepted rules, but take note, however, of the following criteria and how they differ from the brilliant round diamond cut:

Renowned as an extremely precious material, ideal for the manufacture of luxury jewellery, diamonds only reveal the full extent of their brilliance when they are worked and cut. Together we will retrace the history of its cut, the multitude of shapes given to the diamond over the centuries, according to successive modes, in line with the evolution of the know-how of diamond dealers, which today makes it possible to obtain pieces of exceptional quality.

Antique Diamond Cutting

Very early in the history of mankind, diamonds were exploited by ancient civilizations. But it was only later that its cutting really began. Indeed, it was not until the end of the 14th century that the diamond began to be worked, only on its outer part, in order to give it more brilliance, by flattening its surfaces.

Here is a picture of an old cut diamond, with an open breech and a limited number of facets on the pavilion (under the crown). For more information, see the explanations further down on this page.

The invention of diamond cutting

During the Renaissance and at the beginning of the modern era, jewellers gave diamonds a very basic table shape, with few faces, in pink, or a pointed shape. The number of these gradually increased, and they were worn until thirty-two at the end of the 17th century, with a cup known as a Mazarin cut, named after the famous Regent of France.
The technique used by diamond dealers, particularly from Bruges and Burgundy, from the beginning of the 15th century onwards, enabled the diamonds to be cut using a porous cast iron grinding wheel.

Diamond cut from the 18th century

The 1720s saw the rise of an interest in jewellery by aristocrats and the upper bourgeoisie, with the arrival of Brazilian diamonds, which partly replaced Indian mines. Diamonds were encrusted in a metal setting and coupled with other precious stones, most frequently emeralds. However, the shapes given to diamonds change very little: innovation is more in the composition of the jewellery.

Diamond cut from the 19th century

New mines in South Africa and then Australia are bringing impressive quantities of diamonds to Europe, and more specifically to the United Kingdom. Although knowledge of the properties and composition of diamonds is becoming increasingly precise, thanks in particular to Lavoisier's work, cutting is not revolutionising in the strict sense of the word.

Nevertheless, the support is evolving, the metal back is being abandoned for a setting in gold grains: the ornaments and jewellery present exotic, floral shapes, sometimes of ancient inspiration.

As in many areas of craftsmanship, the industrial revolution and globalisation during the 19th century brought about long-term changes in the very way in which diamonds were worked. More modern tools and more varied samples are at the disposal of jewellers, while science allows a better understanding of the cut.

Illustration of an antique cut diamond

Diagram of an antique cut diamond

N.B.: Note the open breech, unlike the modern size (below) where the breech is in closed point. The number of facets is also lower on the old size. The modern cut has many more facets on the pavilion (area under the table and the crown of the diamond). 

Illustration of a round modern brilliant cut diamond

Diagram of a round modern brilliant cut diamond

Nowadays, there is an abundance of possible shapes. Here we will content ourselves with the ten most important ones, which make up the vast majority of diamond cuts. It is worth noting, on the other hand, the recent use of the laser, which makes it possible to work with greater precision and efficiency than traditional tools, and to obtain shapes that were previously impossible.

This form can be considered traditional in jewellery, in the sense that it was one of the first from a historical point of view. However, modern cushion diamonds are more faceted and have a much higher brilliance than their ancestors.

Often square or slightly rectangular (length/width ratio 1.10), its proportions are reminiscent of princess diamonds, but with rounded contours, the cushion cut is still popular today. It has even become very fashionable again in recent years.

This shape would take its name from a diamond cut for the Marquise de Pompadour in the 18th century. Marquise diamonds are distinguished from ovals by two pointed ends, which require precision work. This type of cut produces a diamond with 55 facets, for a classic length/width ratio that can vary from 1.75 to 2.25. Like oval diamonds, they are suitable for long, thin fingers, while giving the illusion of a larger surface area.

How is a diamond cut? The different stages

Before reaching the final result, and obtaining a real brilliant and cut diamond, ready to be set, four main steps are necessary: cleavage, sawing, roughing and faceting. In order to fully understand the way in which the diamond is worked, it is necessary to detail these successive operations.