88Facets Bespoke jewelry request

The four Cs — and the fifth one every jeweller knows but rarely mentions

Guides

The four Cs — and the fifth one every jeweller knows but rarely mentions

March 2025 · 6 min read

Cut, colour, clarity, carat. The four Cs are the standard framework for understanding diamonds. They are also, on their own, an incomplete picture.

The four Cs were developed by the Gemological Institute of America in the 1950s to give buyers a standardised language for comparing diamonds. They are genuinely useful. But after two decades of placing diamonds in front of clients, we believe there is a fifth quality that matters just as much — and that almost nobody talks about.

A brief account of the four

C
Cut
The proportions, symmetry, and polish of a diamond. Of all four Cs, cut has the most direct impact on how a diamond looks. An excellent cut transforms even a modest stone. A poor cut wastes even a flawless one.
C
Colour
Graded D (colourless) to Z (visibly yellow). The difference between D and G is imperceptible to most eyes, particularly in a yellow gold setting. The premium for D-colour is real; whether it is visible is another matter.
C
Clarity
The presence of internal inclusions or external blemishes. Most inclusions are invisible without magnification. An SI1 stone that is eye-clean is indistinguishable from a flawless stone in normal wear.
C
Carat
Weight, not size. Two stones of the same carat weight can look very different in diameter depending on their cut. A well-cut 0.9ct stone will often appear larger than a poorly-cut 1.0ct stone.

The fifth C

Character

Character is not on any certificate. It cannot be measured. But it is the quality that makes two identically graded diamonds feel completely different when you put them next to each other. It emerges from the interaction of all the graded properties — the specific pattern of light return, the way a stone performs in different lighting conditions, the depth of its fire and scintillation.

Some stones are alive. They move with the light in a way that makes you look twice. That quality does not appear on a certificate — but you know it immediately when you see it.

This is why we insist on showing clients stones in person rather than selling from certificates online. The certificate tells you what a stone is. Holding it tells you what it does. Both matter — but the second question is the one that determines whether a ring becomes the first thing someone reaches for every morning.

See the difference in person.

Book a consultation →