Rare Carat and 77 Diamonds Share a Catalogue, and the Overlap Runs Deep

Rare Carat and 77 Diamonds are currently listing 603,099 of the exact same certified diamonds. Not similar stones. Not lookalikes with matching specs. The same physical diamonds, matched by grading lab and certificate number, sitting in two different shop windows at once.

This piece sits under our wider look at why the same diamond turns up at different prices across retailers, which explains the fingerprinting method across the whole index. Here we're narrowing the lens to one pair. The Rare Carat vs 77 Diamonds question lands on our desk constantly, and the honest answer starts with an uncomfortable fact: for a big slice of what these two sell, a buyer isn't choosing between two diamonds at all. They're choosing between two shopfronts for one diamond.

A quarter of each catalogue, give or take

Rare Carat currently shows 2,135,287 active listings. 77 Diamonds shows 2,211,416. They're close enough in size that neither swamps the other, which makes the overlap unusually clean to read.

	Rare Carat	77 Diamonds
Active listings	2,135,287	2,211,416
Also listed by the other	603,099	603,099
Share of catalogue that is shared	28.2%	27.3%
Listed by this retailer only	1,532,188	1,608,317

So 28.2% of Rare Carat stock also appears at 77 Diamonds, and 27.3% of 77 Diamonds stock appears at Rare Carat. The two percentages differ only because the denominators do. It's one set of 603,099 stones, counted from either side of the counter.

That's a solid overlap. Not total, not trivial. A little more than one listing in four on either site has an identical twin on the other.

And the unshared majority matters just as much. Add the two raw catalogues together and you get 4,346,703 listings, which sounds like an enormous pool. Strip out the double counting and there are 3,743,604 distinct diamonds across both sites. Shopping the pair does widen the field, but by less than the headline numbers imply. Worth knowing before spending an evening flicking between two browser tabs, convinced there are twice as many options as there really are.

How we know it's the same stone

Every diamond graded by a major lab gets a report number. GIA issues its own, IGI issues its own, and so on. That number is tied to one physical stone, with its measurements, its inclusion plot and (often) a laser inscription on the girdle that carries the same number.

We match on two things together: the grading lab and the certificate number. Number alone isn't enough, because each lab runs its own numbering and a string of digits could, in theory, exist at two labs for two completely different stones. Lab plus number is the fingerprint. When two retailers list a diamond under the same lab and the same report number, they're describing the same rock.

What we deliberately don't do is match on specs. A 1.5ct G VS2 round with an excellent cut grade describes thousands of diamonds, and they don't look alike once you get them under a loupe. Specs tell you the category. The certificate tells you the stone.

Two caveats, because we'd rather be straight about the method than oversell it. Listings occasionally carry a typo in the certificate number, and a typo breaks the match, so if anything our 603,099 figure leans conservative. And inventory feeds lag; a stone that's just sold through one channel can linger on another for a while before it drops off. The count is a live snapshot, not a sworn inventory.

Why one diamond lives in two shop windows

Most online diamond retail runs on virtual inventory. Manufacturers and wholesalers hold the physical stones and send data feeds out to many retailers at once. A retailer lists the diamond, and when someone buys, the retailer calls the stone in from the supplier. One supplier can feed dozens of storefronts simultaneously.

So a diamond marketplace overlap of this size isn't a scandal, and it isn't a sign anyone's being shifty. It's the plumbing of the trade. Rare Carat and 77 Diamonds present themselves differently to shoppers, but wherever their feeds draw on the same suppliers, the same stones flow onto both sites.

What does differ is everything wrapped around the stone. The setting options. The return window. Resizing, warranty and upgrade policies. Shipping, payment terms, how quickly a real person answers a question about a feather near the girdle. The diamond is identical. The transaction around it isn't.

One detail we love pointing out: imagery often differs too. Two listings of the same stone can carry different photos, different videos, or none at all. If one site shows a clear 360 degree video and the other shows a stock render, that's not two different diamonds. It's the same diamond, better documented in one place. Use the better footage to judge it, wherever it lives.

Shared stones are the rule, not the exception

This pair isn't unusual. Across our live index there are 11,489,177 unique certified diamonds, one row per gemological fingerprint, and a large share of them are listed in more than one place.

Listed at	Unique diamonds	Share of index
One retailer only	6,731,467	58.6%
2 or more retailers	4,757,710	41.4%
5 or more retailers	2,728,980	23.8%
10 or more retailers	1,275,316	11.1%

Those bands are cumulative, so the 10 or more group sits inside the 5 or more group, which sits inside the 2 or more group. Read it as a ladder. Two in every five diamonds have at least one twin. Nearly one in four is sitting at five or more retailers. More than a million are spread across ten or more.

Which reframes the Rare Carat same diamond other retailers question. We haven't broken this pair's 603,099 shared stones down by how many other sites also carry them in this snapshot, so we won't put a number on it. But in an index where a quarter of all diamonds appear at five or more retailers, it would be strange if this shared set were exclusive to these two. Plenty of these stones are almost certainly turning up elsewhere as well. We traced exactly that kind of spread when we followed James Allen stock showing up at three other stores.

Same stone, different number on the tag

Here's where shared inventory stops being trivia and starts being money.

When one certified diamond is listed in several places, there's no rule that says the asking price has to match. Each retailer sets its own margin on top of supplier cost. Some run promotions. Some quote in different currencies and convert at different rates. Some fold a setting or a service into the figure. Across the index, the price for one fingerprinted stone doesn't always agree from site to site, and on an engagement ring budget even a modest gap is real money.

We're deliberately not telling anyone which of these two sites tends to sit higher or lower. Prices move daily and vary stone by stone. A blanket claim in either direction would be wrong for a decent chunk of those 603,099 diamonds at any given moment, and we'd rather send people to live numbers than to a generalisation that's stale by Tuesday.

For that, the 77 Diamonds vs Rare Carat comparison page shows the shared stones with current pricing side by side. And for any single diamond, our where to buy pages list every retailer carrying that exact certificate, so the full spread is visible before anyone commits.

Shopping a shared diamond properly

A few habits make the overlap work for the buyer rather than against them.

1. Get the lab name and report number off the listing before falling in love with the photos. If a listing won't show the certificate number, that alone tells you something.
2. Check the report on the lab's own verification tool. Make sure the measurements and grades match what the retailer is claiming.
3. Search that exact number across retailers. If it's a shared stone, the comparison is now a clean one: same diamond, different terms.
4. Compare the total, not the sticker. Setting, shipping, taxes and duties, return window, warranty, upgrade credit. A lower figure with a shorter return window may not be the better deal.
5. Treat marketing language as marketing. If one site calls a stone eye-clean and the other doesn't, the diamond hasn't changed. Check the inclusion plot and the video.
6. Move quickly on a stone you've settled on. A shared diamond can sell through the other channel, and when it does, it vanishes from both.

That last point catches people out more than any other. Two listings feel like a safety net. They aren't. There's one stone, and whoever pays first gets it.

What we're watching next

The 28.2% and 27.3% figures are a snapshot, and we'll keep tracking them. If the shared share climbs, these two catalogues are converging on the same supply, and comparing them becomes almost entirely a comparison of service and terms. If it falls, one of them is sourcing more stones the other can't reach, and the unshared 1.5 million or so on each side becomes the more interesting story.

Either way, the certificate number is the thread that ties it together. 603,099 diamonds, two shopfronts, one report number each. Read the report number first.