Journal›Gemstone Guide›Cut

The 4Cs

Cut

Cut is the most important of the 4Cs.

It determines how a diamond handles light—its brightness, fire, scintillation, symmetry and overall beauty.

A well-cut diamond returns light to your eye, revealing its true brilliance.

A round brilliant diamond held in tweezers above loose diamonds

The Beauty of a Great Cut

Brightness

White light returned for
a bright, lively sparkle.

Fire

Coloured flashes of light created as light interacts with the diamond.

Scintillation

Sparkle from bright and dark patterns created as the diamond moves.

Pattern & Symmetry

Balanced proportions and precise alignment create beautiful face-up appearance.

How Light Works

A well-cut diamond is designed to return as much light as possible to your eye.

Poor proportions may allow light to leak—causing it to look dull, dark, watery, or flat and small.

Excellent Cut

Light enters and is reflected back to the eye.

Diagram showing light leaking out of the sides and bottom of a poorly cut diamond

Poor Cut

Light escapes through the sides or bottom of the diamond.

Round Brilliant Cut Grades

Cut grades evaluate how well a round diamond returns light.
These images show general light performance for each grade.

Excellent / Ideal

Exceptional light return, maximum brightness, sparkle and fire.

Very Good

Great light performance with minor variation in sparkle.

Good

Noticeable light return with slight loss of brilliance.

Fair

Reduced light return and sparkle. More visible areas of darkness.

Poor

Significant light loss with minimal sparkle and brilliance.

Only round brilliant diamonds receive a cut grade from GIA.
Other shapes are graded on other factors; cut terminology can vary by laboratory.

More Than the Overall Grade

Many factors work together to create true optical performance.

Proportions	The foundation of a diamond’s light performance.
Polish	The smoothness of a diamond’s surface.
Symmetry	The precision of facet alignment and placement.
Table %	The size of the table relative to the diamond.
Depth %	The total depth of the diamond.
Crown & Pavilion Angles	Angles that control how light enters and exits.
Girdle	The thin outer edge that protects the diamond.
Fluorescence / Inclusions	Secondary characteristics that can affect appearance and value.

Shape vs. Cut Quality

Shape refers to the outline of the diamond. Cut refers to how well it is cut.
Cut affects how the diamond is proportioned to perform with brilliance.

Round

Oval

Emerald

Cushion

Pear

Radiant

Fancy shapes are graded by laboratories on polish, symmetry,
and proportions—cut terminology can vary.

Key Considerations

Outline

Well-balanced outline with pleasing length to width ratio.

Bow-Tie

Minimize the bow-tie effect for more even brightness.

Table Size & Placement

Table size should suit the shape, with centered placement.

Pavilion & Crown

Well-proportioned crown and pavilion help maximize light return.

Brightness

Look for strong overall brightness with minimal dark areas.

Symmetry

Good symmetry creates a balanced and pleasing appearance.

Face-Up Size Matters

Carat measures weight,
not visible diameter.

Two diamonds can weigh the same but look very different face up. Well-proportioned diamonds appear larger and deliver more presence for the same carat weight.

Ideal Cut

(larger face-up appearance)

Deep / Poor Proportions

(smaller face-up appearance)

Hearts & Arrows

A signature of precision and optical symmetry.

Hearts & Arrows is a precision optical pattern seen in some exceptionally well-cut round brilliants. Arrows are visible from the crown (face-up view), while hearts are visible from the pavilion side—revealed under a scope.

This pattern can indicate strong optical symmetry and excellent light performance, but it is one indicator, not the whole story.

Optical Symmetry

High precision creates balanced patterns and consistent light return.

Seen in Round Brilliants

Found in some well-cut round diamonds—not all.

Arrows View (Face-Up)

Arrows pattern visible through the table (crown side).

Hearts View (Pavilion-Up)

Hearts pattern visible from the pavilion side under scope.

Arrows View

(Face-Up)

Hearts pattern seen from the pavilion side of a hearts and arrows diamond

Hearts View

(Pavilion-Up)

Cut