Diamond reference
Diamond cuts
& the 4Cs.
Shape describes a diamond’s outline. Cut quality describes its craftsmanship and interaction with light. The 4Cs—cut, color, clarity, and carat weight—provide a shared language for describing diamond quality.
Shape and cut style
Popular diamond
outlines.
People often use “cut” when they mean shape. Shape is the face-up silhouette; cut style is the arrangement of facets. Some familiar names—such as emerald cut—communicate both.
ShapeThe outline seen from above: round, oval, square, pear, or another silhouette.
Cut styleThe facet pattern, such as brilliant or step cut, that influences the diamond’s visual character.
Round brilliant
A circular outline with brilliant-style faceting designed for strong light return.
Oval
An elongated brilliant shape that can appear larger face-up than a round of similar weight.
Princess
A square or rectangular brilliant cut with pointed corners and lively sparkle.
Cushion
A square or rectangular outline with softened corners and several facet-pattern variations.
Emerald
A rectangular step cut with cropped corners and a broad, hall-of-mirrors appearance.
Radiant
A square or rectangular brilliant-style cut with trimmed corners and energetic sparkle.
Pear
A brilliant-style outline that combines a rounded end with one tapered point.
Marquise
An elongated brilliant shape with curved sides and two pointed ends.
A shared quality language
Understand
the 4Cs.
No single C tells the whole story. The four factors work together, and their importance depends on the design, setting, visual preference, documentation needs, and budget.
Cut
Describes the craftsmanship of the facet arrangement and proportions—and how effectively the diamond returns light as brightness, fire, and scintillation.
Excellent · Very Good · Good · Fair · PoorGIA gives this overall cut grade only to standard round brilliant diamonds in the D-to-Z color range.Color
For diamonds in the normal color range, the grade describes the relative absence of color. The scale begins at D and continues through Z.
D–F colorless · G–J near colorless · K–Z increasing colorFancy-color diamonds are evaluated through a different color-grading system.Clarity
Describes the relative absence of internal inclusions and external blemishes, evaluated by a trained grader under 10× magnification.
FL / IF · VVS1–2 · VS1–2 · SI1–2 · I1–3The type, size, number, position, and visibility of characteristics all matter.Carat weight
Measures how much a diamond weighs—not how wide or large it appears when viewed from above.
1.00 ct = 200 milligrams = 100 pointsTwo diamonds with equal weight can have different dimensions, appearance, quality, and value.Reading a specification
One stone,
several details.
A diamond description combines measurements and grades. Each detail answers a different question about the stone.
1.20 ct oval brilliant diamond · G color · VS2 clarity · Excellent polish · Very Good symmetry
The face-up shape and brilliant-style facet arrangement.
The diamond’s weight—not its face-up dimensions.
A grade within the near-colorless range.
A very slightly included clarity grade.
Finish assessments reported separately. Because this is an oval, these are not an overall GIA cut grade.
For fancy shapes: review the outline, length-to-width proportions, symmetry, polish, face-up light performance, and setting protection in addition to the 4Cs. Pointed shapes such as pear, marquise, and princess cuts require particular attention at their corners or tips.
Reference standards: GIA’s 4Cs of Diamond Quality, GIA guidance on diamond cut and shape, and the GIA diamond-shape guide.