Diamonds · Grading
The 4Cs,
read for the counter.
Cut, colour, clarity and carat are how a lab describes a diamond, and how you and your customer compare two. Cut decides how a stone looks. Colour and clarity decide how far a grade can drop before anyone at your counter notices. Carat is weight, not size, and prices step up at round weights such as 0.50 and 1.00. State the four you need, ask for the matching certificate, and we quote.
The Scales
Four grades, one report.
Cut
What it measures
How well the stone is proportioned and finished to return light.
The scale
Excellent, Very Good, Good, Fair, Poor. Polish and Symmetry are graded on the same words.
What to watch
The biggest effect on how a stone looks. On a round, ask for 3X.
Colour
What it measures
How free of tint a white diamond is.
The scale
D–Z: D, E, F colourless; G–J near colourless; K onward shows warmth.
What to watch
Set against the metal. Yellow and rose gold forgive a warmer grade.
Clarity
What it measures
Inclusions and blemishes, seen at 10x magnification.
The scale
FL, IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2, I3.
What to watch
Whether it is eye-clean, which no grade promises on its own.
Carat
What it measures
Weight. One carat is 0.20 grams, or 100 points.
The scale
Stated to two decimals: 0.50, 0.90, 1.00.
What to watch
Price steps at round weights, and the measurements in millimetres.
| The C | What it measures | The scale | What to watch |
|---|---|---|---|
| Cut | How well the stone is proportioned and finished to return light. | Excellent, Very Good, Good, Fair, Poor. Polish and Symmetry are graded on the same words. | The biggest effect on how a stone looks. On a round, ask for 3X. |
| Colour | How free of tint a white diamond is. | D–Z: D, E, F colourless; G–J near colourless; K onward shows warmth. | Set against the metal. Yellow and rose gold forgive a warmer grade. |
| Clarity | Inclusions and blemishes, seen at 10x magnification. | FL, IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2, I3. | Whether it is eye-clean, which no grade promises on its own. |
| Carat | Weight. One carat is 0.20 grams, or 100 points. | Stated to two decimals: 0.50, 0.90, 1.00. | Price steps at round weights, and the measurements in millimetres. |
The scales are the grading labs’ own. Wording varies slightly from lab to lab; the report in front of you is the authority for its stone.
Cut
Cut is the look, not the shape.
Shape is the outline: round, oval, pear, emerald. Cut is how well that outline was proportioned and finished. A well-cut stone sends light back up through the top; a deep or shallow one leaks it out of the sides and looks darker or glassy, whatever its colour and clarity.
A report grades three things here. Cut is the overall grade, Excellent down to Poor. Polish is the finish of the facets. Symmetry is how precisely they line up. Both run on the same Excellent-to-Poor words. A round graded Excellent on all three is what the trade calls 3X, and it is the safe ask when you are buying a round you have not seen.
A fancy shape (oval, pear, marquise, cushion, emerald, radiant, princess) gets no overall cut grade from GIA; its report shows Polish and Symmetry only, so the best it can carry is Excellent/Excellent, often called 2X. For a fancy shape, judge the cut from the measurements and the image: the length-to-width ratio, a bow-tie shadow across the middle of an oval or pear, and whether the stone looks its weight from the top.
Colour
Colour is read against the metal.
White diamonds are graded D–Z. D, E and F are colourless. G, H, I and J are near colourless, and face up white to most customers once set. From K down, a warm tint shows. Each step is small; side by side on a grading tray you can see it, on a hand across the counter you usually cannot.
The setting changes the answer. White gold and platinum show tint, so they suit the upper grades. Yellow and rose gold warm the stone anyway, so a lower grade in the near-colourless range reads the same once set. Buy the grade the finished piece needs, not the highest one on offer.
Diamonds with a real colour (yellow, pink, blue) are graded on a separate scale by intensity: Faint, Very Light, Light, Fancy Light, Fancy, Fancy Intense, Fancy Vivid, with Fancy Deep and Fancy Dark for darker tones. For those, the depth of colour is the grade, and the D–Z scale does not apply.
Clarity
Clarity is graded at 10x, sold at arm's length.
The scale runs FL (flawless) and IF (internally flawless), through VVS1 and VVS2 (very, very slightly included), VS1 and VS2 (very slightly included), SI1 and SI2 (slightly included), to I1, I2 and I3 (included). The grade describes what a trained grader sees under 10x magnification, not what a customer sees.
What the customer sees is whether the stone is eye-clean: nothing visible from normal viewing distance without a loupe. Eye-clean is not on any report. It depends on what the inclusion is, where it sits, and the shape: brilliant cuts such as round and oval hide inclusions well; step cuts such as emerald and Asscher, with their open, mirror-like facets, show them. Many VS2 and SI1 stones are eye-clean and some are not, so for those grades look at the image or the plot, or ask us to confirm it.
Carat
Carat is weight, not size.
One carat is 0.20 grams, divided into 100 points, so a 0.50 carat stone is a fifty-pointer. Prices step up at the round weights buyers ask for: 0.50, 0.70, 0.90, 1.00, 1.50, 2.00. A stone just under a step, a 0.95 against a 1.00, faces up almost the same and costs less per carat. If your customer wants the look rather than the number on the certificate, quote them just under the step.
Carat is weight, not size. Two stones of the same weight can look different sizes from the top: a deep stone carries weight below the girdle where nobody sees it, and some shapes (oval, marquise, pear) spread wider for their weight than a round does. Check the measurements in millimetres on the report, and quote to the size your setting needs as well as the weight.
Small stones are sold differently. Melee, the small diamonds in a pavé band or a halo, is bought by sieve size, points or millimetres and graded in ranges (a colour range and a clarity range) rather than stone by stone, and is not individually certified. Ask for it on the melee page.
Lab-Grown & the Labs
Same four scales, a different report.
A lab-grown diamond is diamond: the same material, graded for cut, colour, clarity and carat on the same scales. What changes is the report. It states that the stone is laboratory-grown, often with the growth method, and any treatment after growth where the lab records it. Most lab-grown diamonds in the trade are graded by IGI; GIA grades natural diamonds and also reports on lab-grown.
At Clazoire, natural diamonds come with GIA certificates and lab-grown with IGI certificates. They are available on request and ship with the goods, so you and your customer can check the stone against the report. Other labs grade diamonds too, HRD and GCAL among them. A grade is only as consistent as the lab that gave it, so compare stones on reports from the same lab. More on how the two main labs differ for a retailer is in GIA vs IGI for retailers, and our policy is on the certifications page.
Ordering From Us
State the four, we quote the rest.
Shape and carat first, with the size in millimetres if your setting needs one.
Colour and clarity as a range (G–H, VS1–VS2) rather than one grade; a range lets us quote more stones.
For a round, ask for 3X. For a fancy shape, Excellent polish and symmetry, and the ratio you want.
Lab-grown or natural, and the certificate you want with it: IGI on lab-grown, GIA on natural.
For SI clarity, ask us to confirm the stone is eye-clean before you commit.
Certified stones are requested on the diamonds page, melee on the melee page, and a finished piece with its centre stone through the quote form. Every quote is free.
The Specifics
The 4Cs, answered straight.
Cut, for how a diamond looks: it decides how much light comes back to the eye. Colour and clarity matter up to the point where nobody at your counter can see the difference, and carat sets the size class and the price step. A well-cut stone a grade lower in colour or clarity usually shows better than a poorly cut stone a grade higher.
3X is trade shorthand for a round brilliant graded Excellent for cut, polish and symmetry on its report. Fancy shapes get no overall cut grade from GIA, so the best they can show is Excellent polish and symmetry, often called 2X.
Often, but not always. Eye-clean is not a grade: it depends on what the inclusion is, where it sits and the shape of the stone. Brilliant cuts hide inclusions well; step cuts such as emerald and Asscher show them. Judge each SI stone from its image or plot, or ask us to confirm it faces up clean.
Prices step up at round weights such as 0.50, 0.70, 0.90, 1.00, 1.50 and 2.00 carats, because buyers ask for those numbers. A stone just under the step faces up almost the same, and costs less per carat. Carat is weight, not size, so check the measurements too.
Yes. A lab-grown diamond is graded for cut, colour, clarity and carat on the same scales as a natural one, and its report states that it is laboratory-grown. At Clazoire, lab-grown diamonds come with IGI certificates and natural diamonds with GIA certificates, available on request.
Tell us the shape, carat, colour, clarity and cut you need, and whether you want lab-grown or natural. A range such as G–H colour and VS1–VS2 clarity lets us quote more options. Certified stones go through the diamonds page, melee through the melee page, and a finished piece through the quote form. Every quote is free.
Factory-direct · MOQ from 1 · most styles