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A COMPREHENSIVE GUIDE TO
diamond cut
what is diamond cut?
Diamond cut is one of the most crucial aspects in determining the beauty, brilliance, and overall appeal of a diamond. Unlike color, clarity, and carat weight, which describe the material properties or size of a diamond, cut is about the craftsmanship involved in shaping and polishing the stone. Cut encompasses the diamond's proportions, symmetry, and how each facet interacts with light.
the diamond cut scale
The diamond cut scale is a grading system developed primarily by the Gemological Institute of America (GIA) to assess the quality of a diamond's cut, which affects its overall brilliance, fire, and sparkle. The GIA introduced this standardized grading scale in 2005 after extensive research into how different proportions affect a diamond's light performance.
cut grade: excellent
Diamonds with an "Excellent" cut grade reflect almost all of the light that enters them, resulting in exceptional brilliance and sparkle. These diamonds have the best proportions, symmetry, and polish.
Characteristics: Nearly perfect light performance, with minimal light leakage. The facets are well-proportioned and precisely aligned.
Appearance: Maximum brightness and sparkle; often preferred by buyers who want the most visually striking diamonds.
cut grade: very good
Diamonds with a "Very Good" cut reflect most of the light entering them, delivering significant brilliance, but with minor imperfections in proportions or symmetry that slightly affect the light performance.
Characteristics: Good light performance with slight light leakage. The proportions and symmetry are close to ideal but may not be as precisely aligned as "Excellent" cuts.
Appearance: Very bright and sparkly, though subtle differences may be noticeable when compared directly to an "Excellent" cut.
cut grade: good
"Good" cut diamonds reflect much of the light that enters but have noticeable imperfections in proportions, symmetry, or polish that reduce their brilliance.
Characteristics: More light leakage compared to higher grades, often due to less-than-ideal facet angles or alignment.
Appearance: The diamond still appears bright but lacks the same level of sparkle as "Very Good" or "Excellent" cuts.
cut grade: fair
Diamonds with a "Fair" cut grade reflect a limited amount of light, which significantly impacts their brilliance. These diamonds often have poor proportions and symmetry.
Characteristics: Significant light leakage due to suboptimal facet angles or alignment. Proportions may be visibly unbalanced, reducing the diamond’s visual appeal.
Appearance: Less brilliance and sparkle, which may make the diamond appear dull or muted when compared to higher-cut grades.
cut grade: poor
"Poor" cut diamonds reflect only a small portion of light, resulting in minimal brilliance. They often have substantial symmetry or proportion issues, causing them to appear lackluster.
Characteristics: Severe light leakage due to poor facet alignment or overly deep or shallow cuts. These diamonds usually lack sparkle.
Appearance: Minimal brilliance and fire; often appear dim or cloudy, even to the untrained eye. This grade is generally less desirable.
A well-cut diamond is designed to maximize the amount of light that enters through the top, reflects off the inside surfaces, and returns to the eye, creating a captivating sparkle. If the cut is too shallow or too deep, light escapes from the sides or bottom, diminishing its brilliance.
Only round brilliant diamonds receive a standardized cut grade because they have a well-defined, mathematically established set of proportions that affect their brilliance, fire, and sparkle.
Fancy-shaped diamonds (like princess, emerald, oval, etc.) can receive evaluations on factors like symmetry and polish, but they don’t receive the standardized cut grade that round brilliant diamonds do because each shape has a unique facet structure and appearance. Different people may prefer different proportions in fancy shapes based on aesthetics rather than standardized brilliance.
how is cut grade determined?
A gemologist uses a variety of technical and visual factors to determine a diamond’s cut grade:
Brilliance: The amount of white light reflected from the diamond
Fire: The dispersion of light into rainbow colors as it passes through the diamond
Scintillation: The sparkle effect, showing the pattern of light and dark areas and the flashes of light when the diamond is moved
Proportions: Examines the relationships between key measurements in a diamond's anatomy
Symmetry: How precisely the diamond’s facets are aligned and proportioned
Polish: The smoothness of the diamond’s facet surfaces
Weight Ratio: How well the diamond’s weight is distributed to maximize size without sacrificing light performance
Durability: A cut that enhances durability without making the diamond prone to chipping or breaking is ideal
diamond anatomy
1. Depth
2. Girdle
3. Table
4. Crown
5. Pavillion
6. Crown Angle
7. Pavillion Angle
8. Culet
types of diamond cuts
Round Brilliant Cuts: The most popular and traditional shape, featuring 58 facets for optimal light reflection
Fancy Cuts: Non-round shapes including pear, marquise, oval, and heart, each with unique facet arrangements to enhance brilliance
Modified Brilliant Cuts: Variations of the brilliant cuts with modified facets to create unique light patterns
Step Cuts: Rectangular or square-shaped facets arranged in steps, such as those in emerald and baguette cuts, are known for their sleek and elegant appearance
Rose Cuts: A vintage style featuring a flat bottom and dome-shaped crown with triangular facets, offering a softer sparkle and antique charm
Vintage Cuts: Old-fashioned cuts, such as old mine cuts and European cuts, are known for their unique facets and historical appeal
diamond cut vs. diamond shape
While often confused, diamond cut and diamond shape are distinct concepts:
- Diamond Cut: Refers to how well the diamond’s facets are cut and arranged to create brilliance and sparkle. It’s a quality factor that affects the diamond's optical properties.
- Diamond Shape: Refers to the physical form or outline of the diamond when viewed from above (such as round, square, or pear). Shape is a matter of style, not quality.
For instance, “round” is a shape, while “excellent cut” is a cut grade. A diamond's shape affects its appearance, while the cut affects its sparkle and how well it plays with light.