Diamond guide
The Four Cs of diamonds, explained plainly
The Four Cs are cut, color, clarity and carat weight: the system the Gemological Institute of America (GIA) created to grade diamond quality (GIA (opens in a new tab)). It works best when the diamond is graded loose, by a lab with no stake in the sale.
| C | What it measures | How it's graded |
|---|---|---|
| Carat | Weight, not size | 1 carat = 100 points = 0.2 grams |
| Cut | How well the proportions return light | Excellent to Poor (GIA, round brilliants) |
| Color | How close a white diamond is to colorless | D (colorless) to Z |
| Clarity | Inclusions and blemishes at 10× magnification | 11 grades, Flawless to I3 |
Why do we recommend only GIA-certified diamonds?
A GIA-certified diamond is one the GIA has graded and issued a report for. The GIA is a nonprofit, established in 1931, with no interest in where you buy your stone (About GIA (opens in a new tab)).
Many other certificates exist. Some labs are run for profit, with the jeweler's interests in mind rather than yours. A certificate may say a diamond is a certain grade, but would the GIA agree? Often it would not.
That's why, whether you buy from Diamond Works or not, we suggest sticking with a GIA-certified stone. It is the industry standard.
“Diamond Works Jewelry will always portray every stone as exactly what it really is.”
Diamond Works Jewelry
Is carat weight the same as size?
No. Carat is a measurement of weight, not size. One carat is divided into 100 points, so a ½ carat diamond should weigh 50 points (GIA (opens in a new tab)).
Carat is the easiest C to measure, but only when the diamond is loose. Too many jewelers round it. Stones as light as 45 points are often sold as "about" a half carat.
There's nothing wrong with a "light" half carat, but it should cost noticeably less. At Diamond Works, a ½ carat stone is exactly that: 50 points.
What does diamond cut mean?
Cut is how well a diamond's proportions, symmetry and polish send light back to your eye. It drives sparkle, and it changes how big a stone looks face-up.
GIA grades the cut of standard round brilliant diamonds from Excellent to Poor. Two diamonds of equal weight can look and cost very different amounts because of cut.
How is diamond color graded?
For a white diamond, color means how close it is to colorless. GIA grades it from D, colorless, down to Z, which shows a light yellow or brown tint (GIA (opens in a new tab)).
Neighboring grades are hard to tell apart by eye, which is why a lab report matters.
What do clarity grades mean?
Clarity describes internal features (inclusions) and surface marks (blemishes) seen at 10× magnification.
GIA uses 11 grades: Flawless, Internally Flawless, VVS1 and VVS2, VS1 and VS2, SI1 and SI2, and I1, I2 and I3 (GIA (opens in a new tab)). Many stones in the VS range look clean to the naked eye.
Before you buy: a four-point checklist
- Get the report number and look it up in GIA Report Check (opens in a new tab). Make sure the details match the stone.
- Know the weight in points. "About half a carat" isn't a weight.
- Ask how it was made. The FTC Jewelry Guides (opens in a new tab) say a lab-grown stone must be clearly described as laboratory-grown or laboratory-created.
- Compare stones side by side. Differences between grades become real when you see them together.
Diamond questions
Do you recommend GIA-certified diamonds?
Yes. We recommend GIA-certified diamonds. GIA is a nonprofit with no stake in where you buy, and its grading reports are the industry standard. We source loose stones through several diamond companies to find the right one at the best price.
Is a half carat always 50 points?
It should be, but many stores sell stones as light as 45 points as "about a half carat". At Diamond Works, a ½ carat stone is exactly that: 50 points. We always describe every stone as exactly what it is.
How do I check a diamond's GIA report?
Every GIA report has a report number. Enter it in GIA's free Report Check to see the report GIA has on file, and make sure the details match the stone.
Do you sell lab-grown diamonds?
Yes. We offer lab-grown diamonds as well as natural ones, and every stone is described as exactly what it is.
Does a lab-grown diamond have to be disclosed?
Yes. The FTC's Jewelry Guides (16 CFR Part 23) say a lab-grown stone must be clearly described as laboratory-grown, laboratory-created or similar, not simply as a diamond.