Start with the part that is not in dispute
A lab-grown diamond and a mined diamond are the same material. Carbon, in the same lattice, with the same hardness and the same behaviour in light. Place one of each on a table and there is no test you can perform with your eyes, or with a jeweller's loupe, that will tell you which is which.
This is worth saying flatly, because the trade spent years being coy about it. The lab-grown vs natural diamond question is not a question of substance. It is a question of origin, of price, and of what story you want the object to carry.
Note what this does not include. A simulant — cubic zirconia, moissanite — is a different material that resembles a diamond. A lab-grown diamond is not a resemblance. It is the thing.
What genuinely differs
Origin. One formed underground over a span of time it is difficult to hold in your head, and was dug up. The other was grown in a chamber under conditions engineered to imitate the ones that made the first. Both are diamonds by the time anyone sees them.
Price. The gap is large and it runs one way. At the same specification, the lab-grown stone costs a fraction of the mined one, which is why couples choosing an engagement stone increasingly start there and end up with something larger, cleaner, or both, for the money they had.
Supply. Mined supply is finite and has always been carefully managed. Lab-grown supply is a function of how much manufacturing capacity exists, and a great deal has been built. That single fact explains most of what has happened to prices, and it leads directly to the question everyone is too polite to ask.
Can anyone actually tell?
Not by looking, and not by asking a jeweller to look harder. Grading laboratories can, using specialised instruments that read the structural signatures a stone carries from how it formed. It is not a judgement call and it is not contested. The report states which it is, and most lab-grown stones also carry an inscription on the girdle, readable under magnification.
So the honest framing is not that lab-grown diamonds get away with passing as mined. It is that they have no need to. They are graded by the same laboratories, on the same scales, and the report says exactly what they are.
The resale question, without flinching
Here is where most comparisons of lab-grown vs natural diamond go quiet, so let us not.
Lab-grown prices have fallen as capacity has expanded. A stone bought some years ago would not fetch today what was paid for it. That is real, it is the strongest argument against buying one, and you should hear it from us rather than from somebody with a mined stone to sell.
What almost never gets said immediately afterwards is that the resale market for mined diamonds is also unkind. The distance between what a retail customer pays and what a dealer will offer to buy the same stone back has always been wide. Most people discover this exactly once, usually while trying to sell something inherited, and they are always surprised.
Which leaves a conclusion neither side of the argument enjoys. Neither is an investment. If what you want is an asset, buy an asset. Jewellery is not one, and anybody telling you otherwise is answering a question you did not ask.
So which should you choose
If you want the most stone for the money, or a size that would otherwise be out of reach, lab-grown is the obvious answer and there is no catch concealed in it. The material is identical and the grading is independent.
If what you actually want is geological age — the fact that this particular object existed before anything else did, and you are simply borrowing it for a while — then that is a real preference and no argument about carbon lattices touches it. Buy the mined stone. It is not irrational to care where a thing came from.
Which, as it happens, is the whole premise of this house.
Where CEPHI sits in all this
Every stone we work with is a lab-grown diamond. Worth stating plainly, because people occasionally assume a biological commission is some third category of object. It is not. It is a lab-grown diamond, graded independently, on the same scales as any other. What makes it different is not its category but its carbon — some of the atoms in the stone were, until recently, part of a person or an animal you love.
In a biological commission that carbon comes from the person or the animal the piece is for — about five grams of hair or fur, collected and sealed under a documented chain of custody, with a physical Certificate of Biological Origin at the end of it. That is a claim about provenance, not about materials. It changes nothing on the grading report. The entry on diamonds grown from hair sets out how it works.
And Custom is a different thing again: a conventionally sourced lab-grown stone, chosen and set by us, with no biological contribution whatsoever. We keep those two apart deliberately and we always will. A Custom stone carries nobody's carbon, whether it is bought for yourself or as a gift, and no page here will ever imply that it does.
What to do with all this when you are actually buying
Jewellery tends to be sold under conditions designed to make comparison difficult. Low lighting, a great deal of vocabulary, and somebody standing attentively close to you.
The correction is unglamorous. Ask for the grading report and read it before you become attached to anything. Compare stones at the same grade rather than at the same price. And work out in advance whether you are buying a material or a story, because both are entirely legitimate things to buy — but a sales floor will happily sell you the first while charging you for the second.
If you are weighing a one-of-a-kind commission against something in a case, how it works lays out the sequence, and an enquiry costs nothing and commits you to nothing. If what you want is better served elsewhere, we will say so.