The 4Cs of Diamond Quality, Explained by a Jeweler

Cut — the one C you should never compromise

Cut is the only characteristic shaped entirely by human hands, and it governs how a diamond handles light. A well-cut stone returns light through the top of the gem as brilliance, fire and scintillation; a poorly cut stone leaks light through the pavilion and looks dull even at high colour and clarity grades.

For round brilliants, look for an Excellent or Very Good cut grade from an independent laboratory. For fancy shapes like the emerald cuts in our eternity bands, judge the symmetry of the facets and the evenness of the 'hall of mirrors' flashes instead.

Colour — what the D-to-Z scale really means

White diamonds are graded from D (colourless) to Z (noticeably yellow or brown). The differences between neighbouring grades are subtle; most buyers cannot separate a D from an F once the stone is set. That is why G–H diamonds often represent the best value in white gold or platinum.

Fancy coloured diamonds — the pinks, greens and blues — sit on an entirely different scale. Their value rises with the intensity of the hue: Fancy Light, Fancy, Fancy Intense and Fancy Vivid. Our matched Fancy Green pair, for example, owes its colour to natural irradiation over millions of years and is graded as a fancy colour, not on the D-to-Z scale.

Clarity — how clean is clean enough?

Clarity measures internal inclusions and surface blemishes, from Flawless down to Included. Anything graded VS2 or better is typically 'eye-clean' — no inclusions visible without magnification. Because step cuts like emerald and baguette have large open facets, they reveal inclusions more readily than brilliant cuts, so we select higher clarity for those stones.

Carat — weight, not size

Carat is a unit of weight (0.2 grams), not a measurement of diameter. Two diamonds of equal weight can face up very differently depending on cut proportions. Prices jump at 'magic sizes' such as 1.00 and 2.00 carats, so a 0.90 ct stone can offer remarkable value.

Every diamond we sell is accompanied by an independent laboratory report and our certificate of authenticity, and is insured at its full appraised value from the moment it leaves our hands.