Diamond Cut Education

Diamond Cut

Diamond cut does not refer to the diamond's shape (e.g., round, oval, pear), but rather the precision, proportion, and arrangement of its facets and the quality of the diamond's overall finish. The cut is arguably the most crucial factor in a diamond's beauty, determining its brilliance and ability to reflect light.

Importance of Diamond Cut

A well-cut diamond will reflect light internally from one mirror-like facet to another, disperse and reflect it back through the top of the stone. This results in a display of brilliance and fire. Diamonds that are cut too deep or too shallow lose light that spills through the side or bottom, diminishing their quality and value.

Components of Diamond Cut

Table: The flat top surface of the diamond.
Crown: The upper part of the diamond, from the table to the girdle.
Girdle: The intersection of the crown and pavilion, which defines the diamond's perimeter.
Pavilion: The lower part of the diamond, from the girdle to the tip.
Culet: The tiny point at the base. It can also be a small facet parallel to the table.

Assessing Diamond Cut

Factors that influence the quality of the diamond cut include:

Depth Percentage: Ratio of depth to width. Determines if a diamond is cut too shallow or too deep.
Table Percentage: Ratio of the table's width to the diamond's width.
Crown Angle: Determines the amount of fire the diamond exhibits.
Pavilion Depth: Affects the diamond's brilliance.
Girdle Thickness: Can range from extremely thin to extremely thick.
Culet Size: Ideally, it should be nonexistent to small.
Facet Arrangement & Symmetry: Misaligned facets can diminish sparkle.
Polish: Refers to the external finish of the diamond.

Cut Grading Scale

The Gemological Institute of America (GIA) has a cut grading system for round brilliant diamonds:

Excellent: Reflects nearly all the light that enters, producing exceptional sparkle.
Very Good: Reflects most light, resulting in superior fire and brilliance.
Good: Reflects a majority of light, offering good brilliance.
Fair: Allows much of the light to escape from the sides or bottom, resulting in less brilliance.
Poor: Loses most of the light out of the sides and bottom.

Different shapes (e.g., princess, oval, emerald) don't have a standardised cut scale, making it more subjective.

Excellent Cut

Maximum amount of light reflection, brilliance and fire.

Good Cut

Allows a small amount of light to leak from the stone.

View all

Poor Cut

Allows much of the light to escape from the bottom of the stone, Minimising brilliance and fire.

View all

Fancy Diamond Cuts

While round brilliants are the most popular, there are several "fancy" diamond cuts:

Princess Cut: Square or rectangular, known for its brilliance.
Emerald Cut: Rectangular with cut corners, characterised by its step-like facets.
Oval Cut: An elongated version of the round brilliant.
Marquise Cut: Boat-shaped, elongated with pointed ends.
Pear Cut: Resembling a teardrop.
Cushion Cut: A square or rectangular shape with rounded corners.

Each has unique facet arrangements and requires different proportions for optimal brilliance.

Impact on Diamond Value

The cut is often considered the most important of the Four Cs in terms of a diamond's appearance. A high-quality cut can enhance the diamond's value, while a poor cut can drastically decrease it.

Expert Tips

Compromising on Cut: If budget is a concern, it's advisable to prioritise cut over other characteristics, as it plays a pivotal role in the diamond's visual appeal.
Visual Assessments: Always view a diamond in various light settings. Look for areas that are dark or dull as indicators of a less-than-ideal cut.
Certifications: Ensure the diamond comes with a reputable certificate detailing its cut grade.

The cut of a diamond significantly affects its beauty, brilliance, and value. A well-cut diamond will have a play-of-light that is both mesmerising and of high value. Whether you're a jeweller, a collector, or someone looking for the perfect gem for a special occasion, understanding the intricacies of diamond cut is crucial.