The Diamond 4Cs, in Plain Words

The diamond 4Cs are cut, color, clarity and carat. They are the shared language every grading lab and every jeweler on 47th Street uses to describe a diamond, lab grown or mined. Learn them once and you can read any grading report, compare two stones fairly, and spend your budget where your eye will actually notice it. Here they are in plain words, with the trade offs we talk through at the tray every day.

Cut: the C that makes it sparkle

Cut is not the shape. Shape is round, oval, emerald and so on. Cut is how well the stone’s facets were angled and finished, which decides how much light comes back to your eye. A well cut diamond looks bright from edge to edge. A poorly cut one can look glassy in the middle or dark at the sides, even with good color and clarity.

For round diamonds, reports give a cut grade, and Excellent or Ideal is what we usually suggest. For fancy shapes like ovals, pears and emeralds, there is often no single cut grade, so you judge with your eyes and with a few numbers: polish, symmetry, depth, table and the length to width ratio.

Color: how white the diamond looks

White diamonds are graded on a scale that starts at D, which is colorless, and runs down the alphabet as a faint yellow or brown tint grows. Most people choose between D and J for an engagement ring.

The metal changes how color reads. A G or H in a yellow gold setting looks white. In platinum, some people prefer to go up a grade or two. Lab grown diamonds make the higher grades easier to reach, so many of our clients choose D to G without stretching the budget.

Clarity: what is inside the stone

Almost every diamond has tiny marks inside, called inclusions, or on the surface, called blemishes. Clarity grades how many there are, how big, and where. The scale runs:

• FL and IF: flawless and internally flawless, very rare.
• VVS1 and VVS2: very, very slightly included, hard to find even under 10x magnification.
• VS1 and VS2: very slightly included, usually clean to the eye.
• SI1 and SI2: slightly included, sometimes visible without a loupe, sometimes not.
• I1 to I3: included, often visible.

The phrase to know is “eye clean.” That means you cannot see any inclusion at normal viewing distance. For most rings, a VS2 or a carefully chosen SI1 is eye clean and saves money for other things. Step shapes like the emerald cut and asscher show inclusions more, so we usually suggest VS1 or better there. On brilliant shapes like round and oval, the sparkle hides small marks well.

Carat: weight, not size

Carat is weight. One carat is 0.2 grams. Two diamonds with the same carat weight can look different in size, because a deep stone hides weight underneath while a shallow one spreads it across the top. Shape matters too. An oval, marquise or pear looks larger face up than a round of the same weight, because it is longer.

Prices jump at round numbers like 1.00, 1.50 and 2.00 carats. A 0.95 carat stone looks the same on the hand as a 1.00 carat, often for less. It is worth asking about stones just under those marks. Our lab grown diamond prices page explains how carat and price move together.

Fluorescence, polish and symmetry

Below the 4Cs, a report lists a few smaller details. Polish and symmetry describe how cleanly the facets were finished and lined up. Excellent or Very Good is what we look for. Fluorescence describes whether the stone glows under UV light, like the light in some clubs. None or faint is common in lab diamonds and rarely changes how a stone looks in daylight.

How the 4Cs work together

No single C tells you how a diamond will look. They balance each other. Here is how we usually help people set priorities:

1. Choose the shape you love first.
2. Put cut quality at the top. It is the sparkle.
3. Pick a color that looks white in your metal: G or H for most, D to F if you want icy white in platinum.
4. Choose the lowest clarity that is still eye clean for that shape.
5. Let the carat weight land where the budget falls after the first four.

The fifth “C” people mention is the certificate, the grading report. It is where the 4Cs are written down by an independent lab. Every lab grown center stone we offer comes with an IGI or GIA report. Learn how to read one in our guide to IGI certified lab grown diamonds.

See the 4Cs side by side

Reading grades is useful. Seeing them is better. At our showroom at 30 West 47th Street, Suite 806, we can lay a G and an E next to each other, or a VS2 next to a VVS1, and let you look with your own eyes and through the loupe. Most people are surprised how small the visible differences are, and that makes choosing much easier.

To get started, use our loose lab grown diamond request to tell us your shape, carat range, color, clarity and budget. We pull 3 to 5 matching stones and have them on the tray. Or browse lab grown diamond engagement rings and save the settings you like. Then book a viewing or call (212) 642-4345.