Master the 4Cs.
Cut, color, clarity and carat weight are the four characteristics on every diamond grading report. Here’s what each one describes — and how to weigh them for the ring you have in mind.
How a diamond works with light.
Proportions, symmetry and polish decide how much light returns to your eye as brightness, fire and sparkle. High color and clarity grades can’t make up for a poorly cut stone.
Anatomy of a round brilliant
The proportions a grading report measures.
- Girdle diameter
- Table width
- Crown height
- Girdle
- Pavilion depth
- Total depth
- Crown angle
- Pavilion angle
- Culet
Crown — the top, above the girdle. Its facets add fire.
Girdle — the outer edge, where the setting holds the stone.
Pavilion — the lower part, which reflects light back up.
Light return
What proportions do to the light entering the table.
Light reflects from one side of the pavilion to the other and returns up through the crown — the brightness and sparkle you see.
- Light enteringEntering
- Light returned to the eyeReturned to the eye
- Light lostLost
Simplified illustration, not a grading or ray-tracing simulation.
Cut grades
- Ideal
- Excellent
- Very Good
- Good
- Fair
- Poor
On IGI reports, Ideal is the top cut grade for a round brilliant; other shapes are graded from Excellent to Poor. Reports also grade polish and symmetry.
Hearts & Arrows
A symmetry pattern visible in some precisely cut round brilliants through a special viewer — hearts from below, arrows from above. It’s described separately; it isn’t a cut grade.A symmetry pattern visible in some precisely cut round brilliants through a special viewer. It’s described separately; it isn’t a cut grade.
Put cut first. Read the cut, polish and symmetry grades together, then look at the stone itself in photos or video.
From colorless to light yellow.
White diamonds are graded on a D-to-Z scale that measures the absence of color. D is completely colorless; toward Z, a yellow or brown tint becomes easier to see.
G–J · Near colorless
Little color is noticeable face-up, especially once the stone is set. A common balance of appearance and price.
Illustrative colors — your screen is not a diamond grading tool.
Compare stones in the same light, and think about your metal. Platinum and white gold show a tint more readily; yellow and rose gold can complement a warmer grade.
Fancy-color diamonds — pink, blue or intense yellow — are graded on a separate scale, where more color is the point.
Tiny features, graded at 10×.
Clarity describes internal inclusions and surface blemishes, assessed under 10× magnification. Their size, number, position and nature all shape the grade.
Minor inclusions that a skilled grader sees only with effort under 10× magnification.
Inclusions drawn larger than life for illustration. Not an actual 10× view or a grading simulation.
Neighboring grades often look the same without magnification. Judge the stone in photos or video, and pay for the clarity you can actually see.
A grade describes the stone as a whole. Where an inclusion sits — under the table or near the edge, where a setting may cover it — matters too.
Weight, not size.
A carat is a unit of weight: one carat equals 0.2 grams, or 100 points. How large a diamond looks also depends on its shape and proportions.
- Typical diameter
- ≈ 6.5 mm
- Weight
- 0.20 g
- Points
- 100
Select a stone to compare. Stones are drawn to relative scale using typical diameters for a well-proportioned round brilliant; actual measurements vary, so check the report.
Dashed outline: 1.00 ct for comparison. Typical diameters for a well-proportioned round brilliant, shown to relative scale; actual measurements vary.
Center stone or total carat weight?
Center-stone weight describes the main diamond only. Total carat weight (ctw) adds up every diamond in the piece — so compare like with like.
When choosing
Read the millimeter measurements next to the carat weight. Price doesn’t rise in simple proportion to weight, and two stones of the same weight can face up at different sizes.
Shape is the outline you fall for.
Shape describes a diamond’s outline; cut describes how well it’s fashioned. Choose the silhouette you love, then compare the 4Cs within it.
Round
The classic brilliant outline, faceted for brightness and sparkle. A timeless choice that suits almost any setting.
View the Luna Round SolitaireCollection: shapes in the AIOVO ring collection. Custom: available through AIOVO Custom Design. Shape order is not a ranking of quality.
Your 4Cs, on record.
Every AIOVO center stone of 1 ct and above comes with an IGI grading report. It records the stone’s origin, measurements and 4Cs, so you can compare exactly what you’re choosing.
Where the 4Cs appear on a report
Illustrative field list, not an IGI document. Fields vary by report and cutting style.
Put the 4Cs to work.
Explore lab-grown diamond rings, or tell us the shape and grades you have in mind and we’ll design around them.
Questions about a stone? Contact Customer Care