Guide to Diamond Cut

Guide to Diamond Cut

To many, cut is considered the most important of aspect of a gemstone’s quality and value. Diamond cut affects some of its optical and physical properties including how it reflects light and “sparkles.”

The Diamond Cut Process

Diamond cut refers to how the jeweler physically cuts the diamond stone into its shape and to the proportions and symmetry that achieve optimal light dispersion, which affects a diamond’s quality and price.

Each diamond is cut to very exacting standards. Let’s look at the process to cut a beautiful diamond to better understand the terminology the jewelry industry uses to explain diamond cut factors.

The most common cut, the round brilliant, has 58 facets, or small, flat, polished planes designed to yield the maximum amount of light reflected back to the viewer.

A diamond’s light reflection, known as brilliance, is an extremely important factor in evaluating the quality of a diamond’s cut. A poorly cut diamond will actually lose light and appear dull.

The widest circumference of a diamond is known as the girdle. Above the girdle of a brilliant cut diamond are 32 facets plus the table, which is the largest and topmost facet. Below the girdle are 24 facets plus the culet, or point.

Diamonds are renowned for their ability to transmit light and sparkle so intensely. We often think of a diamond’s cut as shape (round, heart, oval, marquise, pear), but what diamond cut actually does mean how well a diamond’s facets interact with light. Precise artistry and workmanship are required to fashion a stone so its proportions, symmetry and polish deliver the magnificent return of light only possible in a diamond.

Proportion diagrams will typically include the following information:

Depth: The height of a gemstone measured from the culet to the table.
Table: Located at the top of the diamond, the table is the largest facet of a diamond.
Girdle: Range of girdle thickness.
Culet: Appearance, or lack thereof, of the culet facet.

A diamond’s cut impacts four aspects of the stone’s optical and physical properties.

Achieving the best cut for a diamond reflects in the stone’s final beauty and value. And of all the diamond 4Cs, it is the most complex and technically difficult to analyze. To determine the cut grade of the standard round brilliant diamond – the shape that dominates the majority of diamond jewelry – GIA calculates the proportions of those facets that influence the diamond’s face-up appearance. These proportions allow GIA to evaluate what the best cut for a diamond is, by studying how successfully a diamond interacts with light to create desirable visual effects, such as

Luster: The quality and amount of light that is reflected off just the surface of the diamond. Luster is directly related to the hardness of the stone and the quality of its polish.

Brilliance: The amount of white light that is returned to the eye from both internal and external surfaces. Brilliance is determined by the quality of the diamond’s polish and the number and size of inclusions inside the gem.

Dispersion: The display of spectral or rainbow colors seen coming from the inside of a diamond. Often referred to as “fire,” dispersion is directly related to how well the stone is proportioned.

Scintillation: A diamond will show scintillation, or “sparkle,” when movement is involved. The viewer, the light source or the diamond itself must be in motion for scintillation to occur.

How to Read a GIA Grading Report Video by GIA

How does pavilion depth affect a diamond’s cut?

The distance from the bottom of the girdle to the culet is the pavilion depth. A pavilion depth that’s too shallow or too deep will allow light to escape from the side of the stone or leak out of the bottom. A well-cut diamond will direct more light through the crown.

Related:

• Guide to Diamond Carat Weight
• Guide to Diamond Color
• Guide to Diamond Clarity
• The 4 Cs of Diamonds
• Guide to Diamond Reports
• Guide to Diamond Shapes

Sources:
Jewelers of America
GIA

Last Updated on March 19, 2023 by JewelryNStyle