The size determines the brilliance of the diamond. The quality of the cut of the stone is one of the "4Cs" thus making it possible to estimate the value of a diamond because it determines its brilliance. Indeed, the more a diamond is meticulously cut and presents perfectly symmetrical and aligned facets, the more it will sumptuously reflect the light and thus diffuse an exceptional brilliance.
A cut diamond is distinguished in four parts: the table, the crown, the girdle and the cylinder head.
What are the different sizes?
There are two different types of cuts: round and so-called "fancy".
Diamond cuts can be classified into two main categories of shapes: round cuts and so-called "fancy" cuts.
Among the rounds, there are three sub-categories of sizes: single cut, swiss cut and full cut.
The "single cut" or size 8/8
This is the first necessary step in cutting the brilliant. The diamond obtained has a table, 8 other facets on the crown and 8 facets on the cylinder head.
The “Swiss cut” or size 16/16
This is the second step needed to cut the brilliant. The diamond obtained has a table, 16 other facets on the crown and 16 facets on the cylinder head. Today, this size is mostly used as another intermediate size.
The "full cut" or the "brilliant"
It consists of cutting the diamond so that it reflects the light as much as possible. This ideal cut, very popular today, is made up of 57 facets, namely a table, 28 other facets on the crown and 28 facets on the cylinder head. It is the only diamond cut that is standardized.
They are divided into three subcategories as follows:
Brilliant cuts .
Rectilinear faceted cuts .
Cuts with various facets such as briolettes and roses.
What are the four stages of pruning?
Before cutting a diamond, it is necessary to observe the raw crystal for a long time and to carry out certain calculations to determine which will be the best cut to achieve. Indeed, it is not only a question of avoiding too much loss of material but also of limiting the number of imperfections during the final result.
Four steps are traditionally required to cut a diamond: cleaving, sawing, roughing and polishing.
Today, software exists to scan the rough stone and determine all the possible size options in order to optimize and maximize the size of the stone. It should also be known that all the instruments used to erode the raw crystal must be diamond-coated because diamond is the hardest material and it can only undergo wear by itself (or by laser).
Cleaving, sawing and roughing:
Once a size has been chosen, several steps must be followed to optimize it. The first three are cleaving, sawing and roughing which prepare the raw crystal for polishing which is the last step.
This step involves splitting a rough stone into two or more pieces. This helps to give the gem a nice shape and free it from some imperfections. To do this, the cleaver cuts the diamond in the weak planes of the crystalline structure, also called "cleavage planes", using a fine steel blade on which he strikes a sharp blow. The stone then splits in two, leaving two perfectly flat surfaces. However, splitting is not always necessary: it is necessary to calculate its profitability as accurately as possible. The profession of cleaver is thus one of the most difficult because it entails an enormous responsibility. However, it is not always easy to predict the profitability of a stone at the end of the cleavage: it can be a total failure.
Traditionally, it involved cutting the crystal using a diamond circular saw. Today, the laser has replaced the saw for diamond cutting. However, if the laser makes it possible to start certain cuts that are impossible with a saw, it leaves small streaks on the surface which degrade the sharpness of the result.
The sawing operation must be done while trying to obtain the largest possible table and the hardest possible yoke.
This step focuses on round cuts since it consists of rounding the belt of the crystal to form an outline of a girdle. To do this, the crystal is fixed on a roughing stick which will turn on itself at 1700 revolutions per minute while rubbing the stone on one or two diamond heads. However, the speed is adjustable according to the crystals: the speed is increased for small goods and it is reduced for larger or more delicate stones.
Polishing and symmetry
Polishing is the final step in cutting a diamond. It consists in forming facets in an extremely regular and symmetrical way to obtain the most brilliant diamond possible.
If this process was very delicate and prone to error in the past, the automation of polishing by machines today makes it possible to obtain much more convincing results.
This step is assessed and incorporated into the diamond certificate. Indeed, any error, even minimal, during polishing has an impact on the brilliance of the stone.
The quality of the diamond is judged according to three, or even four, very specific criteria by the jewelry authorities:
• The “symmetry” or “symmetry” which indicates whether the proportions are respected;
• The “polish” or “polish” which indicates the quality of the polishing;
• The “girdle” or “girdle” which indicates the thickness and shape of the girdle. The finer, straighter and more regular it is, the better;
• The mention extra-facette is sometimes added if the tailor has added a facet to hide a natural or size defect.
The first two criteria (symmetry and polish) are judged according to a scale of 5 levels as follows:
• Excellent (Excellent)
• Very Good (Very Good)
• Good (Good)
• Fairly Good (Fair)
• Bad (Poor)
Once these assessments are made, size as a whole is judged on the same scale. Thus, a so-called “Triple Ex” diamond is a diamond that has an “excellent” overall size, symmetry and polish. These diamonds are therefore the best cut and their refraction of light is optimized: they will be the most brilliant.