The 4Cs for lab-grown diamonds (and which one to trade)

Lab-grown diamonds are graded on the same 4Cs as mined stones. The difference is where the value sits: because colour and clarity are easy to grow at the top end, the premium for D/IF is smaller than in mined stones — which changes what you should prioritise.

Cut first

Cut determines how much light comes back. An excellent-cut H-colour stone outperforms a poorly cut D-colour stone in any room. For rounds, look for Excellent cut, Excellent symmetry and Excellent polish. For fancy shapes there is no cut grade, so compare proportions and ask for an image in daylight.

Colour: D–F is not always worth it

In a white metal setting, G–H is usually indistinguishable from D–F to the naked eye. In yellow gold, the stone picks up warmth anyway. The exception is a large stone (2 ct+) where colour concentrates over a bigger area.

Clarity: VS2 is the practical floor

VS2 and above are eye-clean at every size we sell. SI1 can be eye-clean too, but it is stone-by-stone — ask for a video in daylight and a loupe photo. Below SI1, inclusions start to affect light return.

Carat: the cheapest thing to add

Because lab-grown production scales, the price step from 1 ct to 1.5 ct is smaller than in mined stones. If size is the priority, spend there and drop to G/VS2 rather than paying for D/IF at 1 ct.

A sensible allocation

• Engagement ring, 1 ct: Excellent cut, G colour, VS2 — the value point.
• Studs: G/VS2 matched pair; clarity matters less at 5 mm.
• Statement 3 ct+: H/VS1 with an excellent cut, and insist on an ASET or daylight video.

What to ask the seller

Report number and inscription, measurements in millimetres, a daylight video, and the return policy. If any of those is missing, the price is not comparable. Loose lab-grown diamonds →