The four Cs, in plain words

Every diamond is described by four grades. Together they decide how a stone looks and what it costs. Here is what each one means, and how we suggest weighing them.

Cut: where the sparkle comes from

Cut is how well the diamond has been shaped and polished. A well-cut stone returns light to your eye; a poor one lets it leak out of the back. If you spend on one grade first, make it this one.

Colour: how white the stone is

Colour runs from D, with no tint at all, down the alphabet. D to F are colourless. G to J are near-colourless and read as white once set, especially in yellow or rose gold. From K a warm tint begins to show. Our colour scale shows the steps side by side.

Clarity: how clean the stone is

Clarity measures the tiny marks inside a diamond and on its surface, from flawless through VVS, VS and SI. From VS2 most marks cannot be seen without magnification, which makes it a sensible place to start.

Carat: weight, not size

One carat is 0.2 grams. Two stones of the same weight can look quite different in size depending on their shape and how deeply they are cut. An oval or a pear often looks larger than a round of the same carat.

Where to start

• Choose the shape you love first.
• Then the best cut your budget allows.
• Then a colour of G to H and a clarity of VS2 or better, and let carat follow.

Every engagement ring diamond we offer has an IGI or GIA report, so each of these grades is independent.