What I Look for When Sourcing a Diamond
By Don Siah, Founder of Diamond Ateliers
A GIA certificate gives you four numbers: cut, colour, clarity, carat. They are necessary. They are not sufficient.
I have turned down diamonds with excellent grade combinations because something was wrong when I looked at them. I have sourced stones with grades that looked modest on paper because in person they performed beautifully. The certificate describes a diamond. It does not tell you whether that specific diamond is right for a specific ring, worn by a specific person, in the light conditions of their daily life in Singapore.
This is what I actually evaluate when I source a stone for a client.
Cut First, Always
For round brilliants, I will not consider anything below Excellent cut. This is not brand preference or conservatism — it is the recognition that cut is the only factor that determines how well a diamond returns light to the eye, and that all other grade decisions are secondary to this one. A D Flawless stone in a Very Good cut is a worse diamond in practice than a G VS2 in Excellent cut. The light performance difference is visible to anyone who looks at the two side by side.
For fancy shapes — ovals, cushions, pear, radiant, emerald cuts — there is no GIA cut grade, so I evaluate cut quality directly. I look at the proportions against known ranges for that shape. I look at symmetry: is the shape even, are the curves consistent, are the facet junctions meeting cleanly? And then I look at the stone under light and assess what it is actually doing. A well-cut oval should show even, bright light across its entire face. A poorly cut oval will have dead zones, an exaggerated bow-tie, or uneven brilliance — none of which appear on the certificate.
Colour in Context
The colour grade on a certificate is assessed against a white background under controlled laboratory conditions. Once the diamond is in a ring, on a hand, in real light, the context changes completely.
In a platinum or white gold setting, any warmth in a G or H stone is nearly invisible in normal lighting. In yellow gold, even an H or I stone looks white because the warm metal around it shifts the visual reference point. I always consider the intended metal when I look at colour — and I consider the client's sensitivity. Some people are naturally more attuned to colour in diamonds than others. When a client tells me they want it to look as white as possible, I source accordingly. When a client is more interested in size and cut quality, I find room in the colour grade without visible compromise.
What I do not do is buy colour for its own sake. D and E colour carry a premium that is very difficult to justify in terms of visible beauty. If a client's budget is finite — and most budgets are — the money spent upgrading from G to D is better used on carat weight, cut quality, or the setting. I say this honestly in every consultation.
Clarity: The Eye-Clean Standard
The question I ask about every stone's clarity is not "what does it grade?" but "can I see anything with my naked eye at normal viewing distance?" That is the standard that matters in the real world. A stone graded SI1 that is genuinely eye-clean is more beautiful in a ring than a VS1 with an inclusion positioned at the table centre that the certificate has graded conservatively.
For every stone I consider, I look at it without magnification first. Then I look at the clarity plot on the certificate to understand what is there and where. An inclusion near the girdle, under a prong, is practically invisible in a set ring. The same grade of inclusion at the table centre is immediately apparent. The grade does not distinguish between these two scenarios. My eyes do.
The Bow-Tie Problem
For elongated shapes — ovals, marquise, pear cuts — the bow-tie shadow is the thing that a certificate will never catch and that can make or break a stone's beauty. Every oval has some degree of bow-tie. The question is whether it is a subtle darkening that adds depth to the stone or a pronounced dark band that cuts across the middle and draws the eye away from the brilliance.
I reject ovals with strong bow-ties. I do not care what their colour or clarity grades say. A stone with a severe bow-tie is a stone that will look less beautiful in a ring than a lower-graded stone without one. This is the kind of judgment that only comes from looking at a lot of stones over a long period of time, and it is one of the reasons why buying a stone from a photograph — even a high-resolution one — is never the same as seeing it in person.
Natural vs Lab-Grown
I source both natural and lab-grown diamonds for clients at Diamond Ateliers, and my sourcing standards are identical for both. A lab-grown diamond with a poor cut is a poor diamond. A lab-grown diamond with an excellent cut, G colour, and VS2 clarity is a beautiful diamond — and at a fraction of the price of its natural equivalent. I never recommend one over the other categorically; I recommend what is right for each client's priorities and budget.
What I do insist on, for both natural and lab-grown, is a certificate from GIA or IGI. Not because the certificate tells the whole story, but because it gives us a common language and a verified baseline. Everything I described above — the visual assessment, the bow-tie evaluation, the cut quality judgment — happens on top of that baseline, not instead of it.
Why This Matters for Your Ring
When a client commissions a ring from Diamond Ateliers, I do not send them a link to a database and ask them to choose. I source options based on the brief we have discussed, evaluate them against the criteria above, and present what I am confident recommending — with my reasoning. Clients can ask as many questions as they want about why I am showing them a particular stone and not another. Transparency is the only way I know to build the trust that a decision of this scale requires.
Talk to Us
If you would like to understand more about how we source diamonds for bespoke commissions, or if you have a specific stone in mind and want a second opinion, come in for a conversation.
Visit us at 176 Orchard Rd, #03-05 The Centrepoint, Singapore 238843.