The 4Cs describe a diamond. They don't rank it. Get cut and color right first, since those drive how white and bright a stone looks, then choose size and clarity by what you can see.
What the 4Cs are
The 4Cs are carat, color, clarity and cut. The system was built for natural diamonds, and labs like IGI use the same scales for lab-grown stones. A lab-grown diamond graded E color, VS1 clarity is held to the same color and clarity standards as a natural diamond with those grades.
What the 4Cs don't tell you is how a stone looks on a hand. Two diamonds with identical grades can look different in person because of proportions, the location of an inclusion or a faint undertone the grade doesn't capture. The report is the starting point. The photos, video and measurements finish the picture.
Carat: weight, not size
One carat is 0.2 grams. It's split into 100 points, so a 0.75 carat diamond is sometimes called a 75-pointer.
Carat is weight, and weight isn't what people see. They see the top of the stone. A diamond cut deep carries a lot of its weight below the girdle where nobody can see it, so it can weigh more and look smaller than a well-cut stone of lower carat weight.
That's why you should always compare millimeter measurements alongside carat weight. For a well-cut round brilliant, typical diameters look like this:
| Carat weight | Typical diameter (round) |
|---|---|
| 0.50 ct | about 5.1 mm |
| 0.75 ct | about 5.8 mm |
| 1.00 ct | about 6.4 mm |
| 1.50 ct | about 7.3 mm |
| 2.00 ct | about 8.1 mm |
| 3.00 ct | about 9.3 mm |
Notice that going from 1 to 2 carats doubles the weight but only adds about 1.7 mm across. The jump looks smaller than the number suggests. Fancy shapes vary even more, which is covered in the diamond shapes guide.
One more thing on carat: whole carat sizes. For Flawless and Internally Flawless stones, prices really do jump at 1.00, 2.00 and 3.00 carats, because stones that size at that clarity are rarer and cost more to source. VS and VVS lab-grown stones don't work that way. Their cost climbs steadily with weight, with no real jump at the round numbers. Plenty of jewelers add a whole-carat premium to VS and VVS stones anyway. Axiom doesn't. We keep the same margin on every stone, so our prices follow what the diamond actually costs, and you can pick the size you want instead of shopping around the number.
Color: the D-to-Z scale
Color grades measure how much body color a white diamond has, from D (none) down to Z (noticeable yellow or brown).
| Grade | Category | What it looks like |
|---|---|---|
| D, E, F | Colorless | Icy white, even side by side with other stones |
| G, H | Near colorless | A faint warmth that shows next to a colorless stone |
| I, J | Near colorless | Warmth you can pick out, especially in larger stones |
| K to M | Faint | Clearly warm |
D, E and F are the colorless grades, the top of the scale. Every Axiom diamond falls in that range.
Color shows most in larger stones, in step cuts like emerald and Asscher with their big open facets, and anywhere a diamond sits next to other stones. A colorless diamond stays crisp and white in every one of those situations.
You'll often hear that yellow or rose gold "warms the diamond up anyway," so a G, H or even I is fine. That line usually shows up when a store wants to sell a lower-color stone at a colorless price. A colorless diamond against gold is a sharp, bright contrast, and that contrast is the point of the look. With Axiom you get D to F color in any metal, priced below what traditional retailers charge for warmer stones.
Some lower-color lab-grown diamonds can also carry a faint gray or brown tint that the letter grade doesn't fully describe. Sticking to D, E and F keeps that out of the picture. Watch the video either way.
Clarity: what you can see vs what a grader sees
Clarity describes inclusions (internal features) and blemishes (surface features) as seen by a trained grader at 10x magnification. The scale runs from FL (Flawless) down to I3 (Included).
The question that matters for a buyer isn't "how high is the grade" but "can I see anything at normal viewing distance, and where is it." An inclusion under a prong or near the edge is a different story from one sitting in the middle of the table.
Axiom only offers diamonds graded VS2 or higher. At that level, features are small enough that they're hard to find even under magnification. Step cuts like emeralds have big open facets that show more, so it's worth a closer look at the video there. The clarity grades guide covers every grade with a full chart.
Cut: where the sparkle comes from
Cut is about how well a diamond handles light. Proportions, symmetry and polish decide how much light comes back up through the top of the stone and how much leaks out the sides or bottom.
Cut does the most for sparkle. A poorly cut stone leaks light and looks dull, whatever its color or clarity. It can also look smaller than its carat weight because the weight is hiding in a deep pavilion.
On a lab report, cut shows up as three grades:
- Cut (overall proportions and light performance)
- Polish (the finish on each facet)
- Symmetry (how precisely the facets line up)
"Triple Excellent" means all three are graded Excellent. Every Axiom diamond carries Excellent cut, polish and symmetry on its IGI report. For fancy shapes, still look at the measurements, facet pattern and video, since proportions change the look more than the grade alone shows.
Where to spend and where to save
If you're working to a budget, this order gets the most from it:
- Pick the shape. It changes the look more than any grade.
- Hold firm on cut. This is the C people notice without knowing why.
- Choose size by millimeters. Decide how big you want it to look on the hand, then check the measurements, not just the carat number.
- Don't compromise on color. Colorless is what makes a diamond read as white in any metal and any light. Every Axiom diamond is D, E or F, so this one's already handled.
- Set clarity by what's visible. Once nothing shows at normal viewing distance, higher clarity grades may not change the look much, depending on the inclusion pattern.
- Verify the report. Check the report number, measurements and lab-grown disclosure before checkout.
Reading the 4Cs on an IGI report
An IGI lab-grown diamond report lists the shape and cutting style, measurements in millimeters, carat weight, color grade, clarity grade, cut grade where one is issued, polish, symmetry and fluorescence. It also states that the diamond is laboratory-grown and usually notes the growth method and whether post-growth treatment was detected.
The growth method will be one of two:
- CVD (chemical vapor deposition): the diamond is grown layer by layer in a vacuum chamber, as carbon from a heated gas settles onto a thin diamond seed plate.
- HPHT (high pressure, high temperature): a small diamond seed is placed in a press with carbon and exposed to the kind of heat and pressure found deep underground, which grows new diamond around it.
Both methods produce real diamond, and neither is better by default. The grades on the report are what tell you about the stone. Our lab-grown vs natural guide covers the two methods in more detail.
A report records what the lab found. It isn't an appraisal, an insurance value, or a promise about future value. Keep it with your purchase records. You'll want it for insurance and for your jeweler.