A large diamond — three, five, ten carats or more — certified or not, mounted or loose: to whom should you sell it? A dealer and diamond merchant examines it in front of you, by appointment in Paris at 22 rue Drouot or in London at 100 Hatton Garden, and buys it for its own account.
The price of a diamond is set per carat, and the price per carat rises with weight: large stones are rare. Beyond two carats, a colour grade, a clarity grade, a fluorescence or a cutting proportion separate considerable sums, and serious buyers can be counted, in France as abroad. The house buys these stones for its own stock and places them with its clients, without their ever being exhibited. The house also sells polished diamonds to the trade; it reads a stone as a merchant does. For a smaller stone or a family solitaire, see sell a diamond.
Six points, examined in front of you. The four Cs in detail: diamond appraisal.
Dealers' price grids move in steps: 1, 1.5, 2, 3, 4, 5 and 10 carats. A stone of 2.01 carats is not priced like one of 1.98; weighing to the hundredth says so.
From D, colourless, to Z. On a large stone, a single grade weighs heavily. Fluorescence is read too: when strong, it can veil a white stone.
From IF, flawless under the loupe, to P3. Beyond two carats, the position of an inclusion counts as much as its grade: under the table it does not read as it does at the edge.
Brilliant, pear, cushion, emerald, oval, Asscher, marquise, heart: a fine shape and correct proportions are paid for. The house seeks fine cuts and rare shapes.
For a diamond, the reference is the GIA: a recent certificate secures the reading and reassures the final buyer. An older certificate, another laboratory or no certificate at all prevents nothing — we read the stone ourselves before speaking of price.
An old mine or old European cut of several carats is sought after in its own right — how to recognise them (in French). Beyond Z, a diamond becomes a coloured diamond: sell a coloured diamond.
By appointment, in Paris or in London. No consignment, no catalogue, no sale date to wait for.
By telephone or WhatsApp, a few photographs and the certificate if there is one: a first opinion within 24 hours, complimentary.
In private, by appointment, at 22 rue Drouot or 100 Hatton Garden. The stone is verified, weighed or measured without unsetting, then read. It never leaves your sight.
We tell you what the stone is, then what we offer for it, at the market price. You remain free to compare; we encourage it.
Once agreed, by bank transfer, whatever the amount — no fees, no commission. Your identity document is required, as for any purchase by a professional.
Your photographs are neither published nor passed on. Remote appraisal, in detail · Selling from the UK and Europe
A stone that has passed through a public sale has been seen by the whole market; its result circulates. The discreet collectors, those who pay the most, prefer a stone of first hand, that no one has exhibited. That is why the house pays more for a stone brought to it directly than for one bought in the room. To compare the two routes, with the figures: auction or dealer.
To a diamond merchant who buys for its own account and can make you a firm offer. Altmann Collection examines your diamond in front of you, by appointment in Paris or London, with or without a certificate, tells you what it is worth on the market, and then you decide.
To a dealer who buys it directly, for its stock. The stone is neither consigned nor exhibited: the offer is made on the spot and payment follows agreement, the same day. At auction, several months often separate consignment from settlement, fees deducted.
Diamond merchants and dealers who buy for their own stock. Altmann Collection buys certified diamonds — GIA first of all —, mounted or loose, whatever their weight.
Because the price is set per carat and the price per carat rises with weight: large stones are rarer. It also moves in steps — 1, 1.5, 2, 3, 4, 5 and 10 carats —, hence the importance of weighing to the hundredth.
No. A recent GIA certificate makes the reading easier and reassures the final buyer; it is never a condition. Without a certificate, or with an old one, we read the stone in front of you and tell you what it is before speaking of price.
No, never before the opinion. The weight of a mounted stone is approximated by its measurements, without unsetting; a period or signed mount may be worth more than the diamond alone.
Yes. The house receives in London by appointment at its office, 100 Hatton Garden, EC1N 8NX, in the jewellery quarter. Write first by WhatsApp or e-mail with photographs; the appointment is fixed around the house's visits.
Yes. Once agreed, the same day, by bank transfer, whatever the amount — no fees, no commission. Your identity document is required, as for any purchase by a professional.
Verifiable facts, reviewed in October 2026. For a specific case, the appointment settles the matter.
1 carat = 0.20 gram. In a well-proportioned brilliant cut, a one-carat diamond measures about 6.5 mm across, two carats about 8.1 mm, three carats about 9.3 mm.
Colour from D (colourless) to Z; clarity from IF (flawless under the ×10 loupe) to P3 (piqué); fluorescence from none to very strong.
A seller is paid by bank transfer or cheque: French law does not allow cash for this trade. Expect a dated purchase document, and nothing deducted from the figure agreed. French law requires a dealer in precious objects to record each purchase and the identity of the seller. Bring a passport or identity card: it protects you as much as us.
A photograph and the certificate, if there is one, are enough to begin: first opinion within 24 hours, then an appointment in Paris or London.
Request an opinion+33 7 81 11 49 29