Why the 4Cs exist
The 4Cs are a shared vocabulary for describing a diamond: cut, color, clarity and carat weight. Two stones that look alike at a glance can differ in each of these ways.
No single C decides everything. The most beautiful stone for you is usually a balance, with the qualities that matter most to your eye given priority.
Cut: the source of sparkle
Cut describes how well a diamond has been proportioned and polished, not its shape. Facets that are well angled return light to your eye as brightness, fire and scintillation. Facets that are too shallow or too deep let light leak out.
Of the four, cut has the greatest influence on how lively a diamond looks. A well cut stone can seem more brilliant than a larger, poorly cut one.
Color: the D-to-Z scale
For white diamonds, color grading measures how little body color a stone has. The scale runs from D, which is colorless, through to Z, where a light yellow or brown tint becomes easier to see.
The differences between neighboring letters are subtle and often only visible when stones are compared side by side, face down, under controlled light. Setting metal also affects perception: a warm yellow gold can flatter a slightly warmer stone.
Clarity: from FL to I3
Clarity describes the tiny natural features inside or on a diamond, called inclusions and blemishes. The scale runs from Flawless (FL) and Internally Flawless (IF), through Very Very Slightly Included (VVS1, VVS2), Very Slightly Included (VS1, VS2) and Slightly Included (SI1, SI2), down to Included (I1, I2, I3).
Many inclusions cannot be seen without magnification. What matters is whether a feature is visible to the unaided eye, and where it sits in the stone.
Carat: weight, not size
A carat is a unit of weight, equal to 0.2 grams. It is not a measure of how large a diamond looks. Two stones of the same weight can appear different in width depending on their shape and how the weight is distributed.
If face-up size matters to you, ask for the millimeter dimensions as well as the carat weight.
Reports and lab-grown diamonds
Independent gemological laboratories examine diamonds and issue grading reports describing the 4Cs. A report is a useful record because it gives an impartial description of the stone.
Lab-grown and natural diamonds are both real diamonds: chemically, physically and optically the same material, carbon in a crystal structure. They differ in origin, and they are graded on the same 4Cs.
- Cut: proportion and polish, which drive sparkle
- Color: how colorless a white diamond is
- Clarity: the presence of internal or surface features
- Carat: weight, not visual size