Diamond — styles you will see at the showroom.

What to look at

Colour, clarity, cut and carat — and cut is the one that shows. Two stones of identical weight and grade can look nothing alike: a well-proportioned brilliant throws light back at you from across the counter, a deep or shallow one leaks it through the bottom and reads flat. Ask for two of the same size side by side and the difference stops being theory.

Clarity is the grade people overpay for. Anything from VS down is eye-clean at arm's length, and the money saved there buys a visibly better cut. For stones of any size ask for the laboratory report and check that the number laser-inscribed on the girdle matches it.