There is no one figure — there are three
Ask three people what a diamond is worth and you will be given three answers, all of them honest. Retail replacement value is what an equivalent stone would cost in a shop today, and it is the figure an insurer wants. Fair market value is what an unhurried private buyer would pay. A dealer's cash offer is lower again, because the dealer has to fund the stone, hold it and find that private buyer themselves.
For diamond jewellery the spread between the three is wide. A natural stone that would be replaced at retail for a given sum commonly changes hands privately at something like thirty to fifty percent of it, and a dealer paying cash today sits nearer twenty to thirty-five. That is not anybody cheating. It is the difference between a shop's price, which includes the shop, and a wholesale price, which does not.
- Retail replacement — for insurance. The highest of the three, and never a sale price.
- Fair market value — a private sale between willing parties, given time.
- Cash offer — a dealer taking the stone today and carrying the risk of it.
A grading report is not a valuation
A GIA report describes a stone: shape, weight, measurements, cutting proportions, colour, clarity, and any treatments. It states no value at all. GIA is unusually plain about this — it does not appraise or certify what is submitted to it, and its reports are not valuations, appraisals or guarantees. The trade calls them certificates anyway, which is where a great deal of the confusion starts.
The distinction matters because the report is the input, not the answer. An appraiser reads the grades and applies a market to them, and the market is the part that moves. A report written in 2009 still describes the stone perfectly well and tells you nothing whatsoever about 2026.
One recent change is worth knowing if the stone is laboratory-grown. GIA has stopped applying the colour and clarity nomenclature it developed for natural diamonds to lab-grown stones, and now issues a quality assessment describing them as Premium or Standard instead. A lab-grown stone bought a few years ago with a full four-Cs report would not be graded that way today.
How the four Cs actually move the price
Carat weight does the most, and it does not do it in a straight line. Price per carat rises as stones get larger, so the total price rises faster than the weight — a two-carat stone is well over twice a one-carat of the same quality, not twice. Larger rough is rarer, and the market prices the rarity, not the gram.
The steps sit at the round and half weights the trade sells on: half a carat, three-quarters, nine-tenths, one carat, one and a half, two. A 0.99 ct stone and a 1.01 ct stone are indistinguishable on a hand and can be a fifth apart on price, because one of them gets to be called a carat. If you are buying, that step is a discount waiting to be taken. If you are selling, it is why the figure you hoped for was based on the wrong side of a threshold.
Colour and clarity are graded far more finely than the eye can read. D to F is the colourless band and carries a premium of roughly a third over a well-chosen G at the same everything else, though almost nobody can see the difference once the stone sits in yellow gold. An eye-clean SI1 looks identical to a VS1 at arm's length and costs meaningfully less. Cut is the exception: it is the only C that changes how the stone behaves across a room, and it is the one most often traded away for weight.
- Carat: price per carat steps up at 0.50, 0.75, 0.90, 1.00, 1.50 and 2.00 — the steps are where money is lost and found.
- Colour: D–F is a premium band; G–H faces up white in most settings, and warmer metal hides more again.
- Clarity: an eye-clean SI1 is indistinguishable from a VS1 without a loupe, and priced as though it were not.
- Cut: the C that decides how the stone looks, and the one most often economised on.
The mount is worth less than you paid for it
On most rings the centre stone is the value and the mount is close to a rounding error. Precious metal is bought back by weight against the spot price, less a refining margin, and the making — the casting, the setting, the finishing, the shop's margin on all three — does not come back at all. A mount that cost four figures to commission is often worth its gold and nothing more.
Small side stones and pavé rarely add much, and can quietly subtract: a melee-set band takes labour to unset and is easier for a buyer to price at zero than to argue about. Do not have the centre stone removed to sell it separately unless a buyer has actually asked for it that way. An unset stone is easier to grade and harder to sell to a person.
Getting an appraisal, and the fee to refuse
A useful appraisal is written by somebody credentialed, who works to a recognised standard, who has gemological training, and who has had the piece in their hands. It names the type of value it states and the purpose it was written for, and it records what could not be examined — a stone in a closed setting cannot be fully graded, and an honest document says so rather than guessing.
Fees are charged by the hour or as a flat fee per item, commonly in the low hundreds per hour depending on the market. An appraiser who wants a percentage of the value they are about to assign has an interest in the size of that value, and the professional bodies treat it as a conflict. Decline it, politely, and find somebody else.
Then read which figure you have been given. An insurance appraisal is written at retail replacement, deliberately high, because its job is to fund the purchase of a like piece from a shop at short notice. It is not what a buyer will pay for your ring and it was never meant to be. Bringing one to a dealer and being offered a third of it is the commonest disappointment in the trade, and it is a misunderstanding rather than an insult.
- Credentials and the standard worked to, stated on the document.
- An hourly or flat fee — never a percentage of the value assigned.
- The type of value and the intended use, named on the face of the report.
- A physical examination, with condition and any limits on it recorded.
- Measurements, plotted characteristics, photographs and a date.
If you are selling it
Work from sold prices rather than asking prices. An asking price is somebody's hope; a sold price is the only evidence there is. Then take at least three offers, and take them from different kinds of buyer, because a dealer, a consignment jeweller and an auction specialist are pricing three different transactions rather than disagreeing about one.
If the stone is significant and has no report, buy one before you sell. A graded stone is legible to every buyer in the market and argues for its own price; an ungraded one is priced by whoever happens to be holding the loupe, and they are not holding it on your behalf. If the stone is laboratory-grown, set expectations low: retail on lab-grown has fallen so far and so fast that resale offers now commonly land between a tenth and a third of what was paid, and sometimes there is no offer at all.
- A dealer or diamond buyer — fastest, lowest, and done in a day.
- Consignment with a jeweller — a commission off the top, and a wait.
- Auction — worth it above a certain quality; the buyer's premium of 20–28% comes out of what a bidder can afford to bid, and the seller's commission comes out of the hammer.
- Private sale — the highest figure, the longest wait, and the one with a safety problem. Meet at a jeweller, and do not ship first.
If you are keeping it, insure it properly
Almost every contents policy caps jewellery, per item or in total, and the cap is usually far below what a ring is worth. Above it the piece has to be scheduled — listed individually, generally against a written valuation — or it is simply not covered for its value. Premiums on scheduled jewellery typically run one to two percent of the sum insured a year.
Two details are worth reading before you rely on the policy. Cover written on a valued basis pays the scheduled sum; cover written on an actual cash value basis pays a depreciated figure and pays it after the loss. And check the wording on a stone falling out of a worn setting, which is the way jewellery is most often lost and the way it is most often excluded. Revalue every three to five years, because a policy written against a decade-old figure will not replace anything.
What a photograph can tell you, and what it cannot
A capture reads the exterior and infers from it. It reads shape, cutting style, the setting and its metal, apparent condition, and spread — the face-up size — from which weight is estimated rather than weighed. That is enough to place a piece in a band, and a band is genuinely useful when you have no idea what you are holding.
It cannot confirm that the stone is a diamond. It cannot rule out moissanite, it cannot separate laboratory-grown from mined, and a yellow-gold setting will warm the apparent colour of anything sitting in it. So take the figure as orientation before you walk into a shop, and take nothing more from it than that. The house does not examine anyone's property and does not pretend a photograph is an appraisal.