What a diamond is
A diamond is carbon crystallised in a cubic structure. It is the hardest natural material known, scoring 10 on the Mohs scale of scratch resistance, although it can still chip if struck.
The 4Cs
The 4Cs, a system developed by the Gemological Institute of America in the mid-twentieth century, describe a diamond's quality.
Cut
Cut describes how well a diamond's facets interact with light: its brightness, fire and scintillation. For round brilliant diamonds, laboratories such as GIA grade cut from Excellent to Poor. Read What is diamond cut?.
Colour
For white diamonds, colour is graded on a scale from D (colourless) to Z (light yellow or brown). Differences between neighbouring grades are subtle. Read What is diamond colour?.
Clarity
Clarity describes internal inclusions and surface blemishes, graded from Flawless (FL) and Internally Flawless (IF) through VVS1, VVS2, VS1, VS2, SI1, SI2 to I1, I2 and I3. Read What is diamond clarity?.
| Clarity grade | Meaning |
|---|---|
| FL / IF | Flawless / internally flawless under 10x magnification |
| VVS1 / VVS2 | Very, very slightly included |
| VS1 / VS2 | Very slightly included |
| SI1 / SI2 | Slightly included |
| I1 / I2 / I3 | Included; inclusions may be visible and may affect durability |
Carat weight
One carat equals 0.2 grams and is divided into 100 points. Carat measures weight, not size: two diamonds of the same weight can look different depending on their cut. Read What is carat weight?.
Shapes
Shape is the outline of the diamond: round, oval, cushion, princess, emerald, pear, marquise, radiant, asscher or heart. See Diamond shapes explained.
Natural and laboratory-grown
A laboratory-grown diamond is diamond, with the same chemical composition and crystal structure as a natural diamond. It is grown by HPHT or CVD and must be identified as laboratory-grown. Gemmological laboratories can tell the two apart. Read The Lab-Grown Diamond Guide.
Reports
A gem report describes the characteristics of one stone. See Certificates & Authenticity and GIA vs IGI.
Reference: Gemological Institute of America, diamond 4Cs (gia.edu). Grading terminology may differ between laboratories.
Frequently asked questions
Which of the 4Cs matters most?
For most people, cut, because it has the greatest effect on how a diamond sparkles. The balance of the other Cs depends on your priorities.
What does VVS mean?
VVS stands for very, very slightly included. It is a clarity grade in which inclusions are extremely difficult to see even under 10x magnification.
Is a lab-grown diamond a real diamond?
Yes. It is diamond. It must always be identified as laboratory-grown.
