How to Choose a Lab-Grown Diamond for Your Engagement Ring

Q: How do I choose the right lab-grown diamond for an engagement ring?

Start with the 4Cs: Cut is most important for brilliance (always choose Excellent or Very Good). Then prioritise Clarity (VS2 or SI1 is usually eye-clean), Colour (F-H range looks white in most settings), and Carat (buy the largest stone that fits your budget after prioritising the other 3Cs).

Q: What cut grade should I choose for a lab-grown diamond?

Always choose Excellent (or Ideal) cut grade for round brilliant lab-grown diamonds. Cut has the greatest impact on brilliance and sparkle. For fancy shapes like oval or cushion, look for Very Good or Excellent cut with good symmetry and polish grades.

Q: Does lab-grown diamond colour matter?

Yes. For white gold or platinum settings, choose F-H colour for a bright, white appearance. For yellow or rose gold settings, G-I colour looks equally stunning at a lower cost because the warm metal tone masks any slight warmth in the diamond.

Q: What clarity grade should I choose for a lab-grown diamond?

VS2 or SI1 are the best value clarity grades. Both are typically eye-clean (inclusions not visible to the naked eye) while costing significantly less than VVS or FL grades. Always view the certificate plot and any available images to confirm the inclusions are not centrally located or visible.

The four Cs — cut, clarity, colour and carat — are the framework used to evaluate any diamond, mined or lab-grown. But for a wearable engagement ring, they don't all carry equal weight. Here's how to use them practically, and what to prioritise when making your choice.

Start with cut

Cut is the most important factor in determining how a diamond looks. It governs how light enters and exits the stone — the brilliance, the sparkle, the fire. A poorly cut diamond of high clarity and colour will look flat and lifeless. A well-cut diamond of modest colour and clarity will look alive.

For IGI grading, look for Excellent or Very Good cut grades. Don't compromise on cut to save budget — it's the factor that determines whether a diamond catches the light across a room.

Colour: good enough is enough

The IGI colour scale runs from D (colourless) to Z (noticeably yellow). For most settings, the difference between D and G is not visible to the naked eye once the diamond is set in metal. Going below H or I can start to show a faint warmth, especially in white gold or platinum settings where the cool metal provides contrast.

Practically: an F or G colour gives you a diamond that looks colourless without paying the premium for D or E.

Clarity: inclusions you can't see don't matter

Inclusions are natural (or in lab-grown diamonds, process-related) imperfections inside the stone. The clarity scale runs from Flawless (FL) to Included (I3). Diamonds graded VS1 or VS2 (Very Slightly Included) are typically eye-clean — you'd need a loupe at 10x magnification to see anything.

SI1 can also be eye-clean, depending on where the inclusions sit. SI2 is more variable. For a ring you'll wear daily, eye-clean is the practical target — not Flawless.

Carat: shape changes perception

Carat measures weight, not size — but weight and visible size are closely related. However, shape affects how large a diamond appears for a given carat weight. Oval and marquise cuts, because of their elongated shapes, tend to look larger than round brilliants of the same carat. Emerald cuts and Asscher cuts tend to look smaller because their light performance is different.

If looking large matters, an oval or marquise gives you more visible diamond for your carat.

Shape: the most personal choice

Shape is entirely aesthetic. The right shape depends on the hand it'll sit on, the setting style, and personal preference. Our most popular shapes are oval and emerald — both suit a wide range of hand shapes and scale well across carat sizes.

If you're buying as a surprise, consider what shapes your partner tends to be drawn to in jewellery and fashion. Elongated shapes (oval, marquise) tend to appeal to people who favour elegant and refined aesthetics. Bold geometric shapes (emerald, radiant) tend to appeal to people with a more architectural or statement-led style.

The IGI certificate

Every Una Diamond comes with an IGI certificate that independently confirms the stone's cut, colour, clarity and carat. You're not relying on our description alone — you have a third-party grading document. Browse our rings or read more about diamond grading to continue your research.