Choosing a stone

The four Cs were invented so dealers could describe diamonds to each other without seeing them. They're a useful shorthand and every stone we sell is graded by them. But they were designed to price stones rather than to help you choose one, and there's a real difference between the two.

Some of what the industry sells hardest makes almost no visible difference once a stone is on a hand. Some of what it barely mentions makes an enormous one. What follows is what we'd tell you across the bench.

Cut

Cut does more work than everything else combined, and it's the one people worry about least.

Cut isn't shape. Shape is whether a stone is round, oval, emerald or pear. Cut is how well it's been made: the angles, the proportions, the symmetry, and whether light entering the stone comes back out or leaks away through the bottom. A well-cut stone looks alive in ordinary daylight. A poorly cut one looks flat no matter what its certificate says.

Two diamonds of identical weight, colour and clarity can look nothing like each other. That difference is cut, and it's visible from across a room.

If you only care about one thing, care about this one.

Colour

Diamonds are graded from D, which is colourless, down through the alphabet to Z, which is faintly yellow. Higher letters are rarer and priced accordingly.

What's less often said is that once a stone is set, the metal around it changes what you see. In yellow gold, the difference between a D and a G is close to invisible, because the gold reflects warmth into the stone regardless. In platinum or white gold, a warmer stone shows more.

So the honest answer is that the right colour grade depends on the setting you're choosing. It's a decision worth making after the metal rather than before it.

Clarity

Almost every diamond formed with something inside it. Tiny marks called inclusions, made when the stone was under pressure hundreds of kilometres underground. Clarity grades how many there are, how large, and where.

The scale runs from flawless down to visibly included, and it's assessed under ten times magnification. That last part matters. Most of the scale describes things you cannot see without a loupe.

The threshold that counts in daily life is whether a stone is eye-clean, meaning whether you can see anything at normal distance. Plenty of stones several grades below flawless are entirely eye-clean, and the difference in what you'd pay is significant while the difference in what you'd see is nothing.

We'd rather put that difference into cut.

Carat

Carat is weight, not size. It's worth separating the two, because they don't move together as neatly as people expect.

A stone can carry its weight deep in its body, where nobody sees it, or spread across its face, where everyone does. Two one-carat diamonds can look noticeably different in size on a hand depending on how they're proportioned. A well-spread stone of slightly less weight often reads larger than a deeper stone of more.

Setting matters here too. A low, wide setting makes a stone look bigger than a tall one does. So does the width of the band beside it.

Where the difference actually shows

If we were choosing for ourselves, in this order.

Cut first, and not narrowly. It's the difference between a stone that looks alive and one that doesn't.

Eye-clean, then stop. Once you can't see an inclusion at arm's length, further grades are buying a certificate rather than a stone.

Colour to suit the metal. Warmer stones in yellow gold, cooler in white.

Carat last. Not because size doesn't matter. It clearly does to some people, and there's nothing wrong with that. But it's the only one of the four you can trade against the others, and a smaller stone cut beautifully will outshine a larger one that isn't.

Certification

Every natural stone we set comes with a GIA certificate confirming its grading. You'll receive it with the piece.

A certificate tells you what a stone is. It doesn't tell you whether you'll like it. We've turned down stones with excellent paperwork because they didn't look right in the hand, and we've bought stones that graded modestly because they were beautiful.

Where our stones come from

Every stone is chosen by Annabel or Isabella before it's set. We buy from a small number of dealers we've worked with for years, and we know where our stones come from.