The 4Cs: which two actually change what you see

The 4Cs are quoted by every jeweller and explained by almost none. Here is what each one does to the stone in front of you, and where the money stops buying anything visible.

Cut — the one that matters most

Cut is not the shape. It is how precisely the facets are angled.

A well-cut stone returns light back up to your eye. A poorly cut one leaks it out of the bottom, and looks dull no matter how large or how flawless it is.

If you optimise for one C, make it this one. A well-cut 0.90ct outshines a badly cut 1.20ct, and costs less.

We stock Excellent and Very Good only.

Carat — weight, not size

Carat measures weight. Two stones of the same carat can look noticeably different depending on how the weight is distributed — a deep-cut stone hides mass underneath where nobody sees it.

Prices also jump at round numbers. A 0.90ct costs meaningfully less than a 1.00ct and is about two per cent narrower across the top. Buying just under a milestone weight is the most reliable way to get more visible stone for your money.

Colour — you are paying for a letter

Diamonds are graded D (colourless) through Z. The difference between adjacent grades is invisible to the naked eye. Even D against H is hard to call without the two stones side by side on a white card.

Buying at G–H rather than D gets you a stone that looks the same in every real setting for meaningfully less.

In yellow gold you can go further still — the warmth of the metal hides a J happily.

Clarity — stop at eye-clean

Almost every diamond, grown or mined, forms with tiny inclusions. Clarity grades how visible they are under 10× magnification.

Anything VS2 or better is eye-clean: you will not find an inclusion without a loupe. Paying up to VVS1 buys you a better certificate and nothing you can see.

We set VS2 and above, so every stone is eye-clean.

Where we would spend

For a solitaire, in order:

1. Cut — Excellent, no compromise
2. Carat — just under a round number
3. Colour — G–H in white metal, up to J in yellow
4. Clarity — VS2, and stop

That order buys the biggest, brightest stone your budget can produce. Reversing it buys a better piece of paper.