Diamond Cut: How Cut Influences Diamond Sparkle

What is diamond cut?

Diamond cut refers to how well a diamond has been shaped and proportioned from the original rough stone.

The quality of the cut determines how effectively light enters the diamond, reflects internally and returns to the eye. When a diamond is cut well, it produces the sparkle that diamonds are known for.

Three important effects are often used to describe how a diamond interacts with light: brilliance, dispersion and scintillation.

Brilliance, dispersion and scintillation explained

These terms are used to describe how light behaves within a diamond.

Brilliance refers to the white light that reflects from the surface and interior of the diamond.

Dispersion, sometimes called fire, describes the flashes of rainbow colours that appear when light is refracted through the diamond.

Scintillation refers to the flashes of light seen when the diamond moves. This effect is created by the contrast between light and dark areas within the stone.

Together, these characteristics create the sparkle that diamonds are known for.

Diamond cut vs diamond shape

It is important not to confuse diamond cut with diamond shape.

The cut describes how well the diamond has been fashioned and proportioned.

The shape refers to the outline of the diamond when viewed from above. Popular shapes include round, princess, oval and marquise, along with many other fancy shapes.

Although shape determines the diamond’s appearance, the cut influences how effectively the diamond reflects light.

Diamond cut grades for round brilliant diamonds

Round brilliant diamonds are typically assigned a cut grade that reflects how well they have been proportioned.

At Lorel Diamonds, the round brilliant diamonds available typically fall into three cut categories.

Excellent / Ideal cut

Diamonds with an Excellent or Ideal cut are crafted with highly precise proportions.

These diamonds are designed to maximise brilliance, fire and sparkle by reflecting the greatest amount of light possible.

Excellent cut diamonds are relatively rare, representing only a small percentage of diamonds available. Because of this, they often command a premium price.

For buyers who prioritise maximum sparkle, an excellent cut is often considered the best option.

Very good cut

Diamonds with a Very Good cut offer light performance that is extremely close to excellent cut diamonds.

In many cases, the difference between very good and excellent cut diamonds is difficult to notice without specialised equipment.

Very good cut diamonds can offer strong light performance while often providing better overall value.

Good cut

Diamonds with a Good cut still reflect a substantial amount of light and maintain a pleasing level of sparkle.

Although they may not reflect light as efficiently as higher cut grades, they can still produce attractive brilliance.

Good cut diamonds can provide a good balance for those who wish to prioritise other characteristics while maintaining a diamond that still performs well visually.

Diamonds graded below good cut are generally less desirable because their proportions allow more light to escape through the sides or bottom of the stone, reducing sparkle.

Brilliant cut vs step cut

Diamonds can also be described by the style of faceting used during the cutting process.

Brilliant cut diamonds are designed with triangular facets arranged to maximise sparkle. The most famous example is the round brilliant cut, which typically consists of 58 facets.

Many other shapes are based on brilliant cutting styles, including princess, marquise and heart shapes.

Step cut diamonds use long rectangular facets arranged in rows. Shapes such as emerald and asscher are examples of step cut diamonds.

These diamonds tend to reflect light in broader flashes, producing a more subtle and elegant appearance compared with the sparkle of brilliant cuts.

What is a diamond facet?

A facet is a flat polished surface on a diamond.

Each diamond contains multiple facets that allow light to enter, reflect and exit the stone. The number and arrangement of these facets influence how the diamond interacts with light.

Brilliant cut diamonds often contain around 56–58 facets, while other shapes may vary depending on their design.

Why fancy shape diamonds do not receive a cut grade

Cut grades are typically only assigned to round brilliant diamonds.

Round diamonds are symmetrical, which makes it easier for grading laboratories to measure their light performance and proportions.

Fancy shapes such as princess, oval or pear have more variation in their proportions. Because of this, an internationally standardised grading system for their cut performance does not currently exist.

https://www.gia.edu/gia-faq-analysis-grading-system-fancy-shape-diamond

Instead, factors such as proportions, symmetry and polish are considered when evaluating their overall quality.

Polish and symmetry

In addition to the 4Cs, other characteristics can influence how well a diamond performs visually.

Polish refers to the smoothness and condition of a diamond’s facets after the cutting process.

Symmetry describes how well the facets are aligned and balanced.

When facets are properly aligned and polished, light can travel through the diamond more effectively, enhancing brilliance and sparkle.

Lower grades in polish or symmetry may reduce light performance and affect the overall appearance of the diamond.

Is diamond cut the most important of the 4Cs?

Many experts consider cut to be one of the most important factors influencing a diamond’s appearance because it determines how the diamond reflects light.

However, there is no single correct approach when selecting a diamond. Each of the 4Cs — carat, clarity, colour and cut — contributes to the overall quality of the stone.

The right balance depends on individual preferences and budget. Some buyers prioritise sparkle and choose a higher cut grade, while others prefer to balance the 4Cs to achieve the best overall combination.