Diamond Market, Week 42, 2026

Price gaps between retailers widened again. For a stone listed in more than one place, the median cross-retailer spread reached 130.6% this week, up from 122.4% in week 41 and the widest of the seven weeks I've been charting. In week 36 it was 71.9%. So in a month and a half it has nearly doubled, and that's the story of the period. One listing shows it better than any median. A 51.79ct I VS2 lab-grown round appeared at $163,073 with one seller and $42,567 with another. Same stone, almost four times the price.

Meanwhile the market kept growing. Active inventory reached a record 46.8 million stones, up 1.1% on the week and 60% since week 36, and total listed value rose 2.05% to $150.8 billion. Cross-retailer overlap slipped to 44.2% from 45.1%, which makes the spread move more striking. Fewer stones are listed in more than one place, yet where they do overlap, the prices sit further apart. The median asking price edged up 0.9% to $1,098, the highest of the window. Price per carat rose to $857.84, but that's still 3% below where week 36 started and well short of the $932 peak in week 38. Median carat size held at 1.3.

Lab-grown share eased to 62.05% from 62.6%. That's its second straight weekly dip from the 63.5% high in week 40. Retirements explain some of it. My sold detection retired 538,800 stones this week against 400,961 genuinely new ones, and lab-grown made up most of that gap: 395,774 gone versus 279,179 new. Natural was closer to even, with 143,016 gone and 121,782 new. (Sold detection only catches some retirements, so the true gone count is likely higher.) The price-to-quality gap between the two origins is as wide as ever. Lab-grown's median sits at $692, or $337 a carat. Natural's is $860, or $1,658 a carat, close to five times as much per carat.

But lab-grown also owned the very top of the market, which deserves some scepticism. A 17.06ct F VVS2 lab-grown emerald is listed at $3.63 million, and four of the five most expensive stones this week are 15 to 17ct F VVS2 lab-grown pieces priced above $3.2 million. Those are aspirational price tags. I'd be surprised to see them sell anywhere near that.

On shapes, nothing rose. Pear was the notable loser: its median fell 27.5% to $752 from $1,038 on almost 330,000 new listings, too many to dismiss as noise. Trillion dropped 35% to $794, but only 982 were listed, so read little into it. The catch-all "other" group fell 52%, which says more about the mix than about prices. Rounds made up 41.9% of new listings, as usual. Cushion ($1,278) and Asscher ($1,201) had the highest medians.

Next week, I'm watching whether the spread keeps climbing or levels off around these highs. A handful of names did 36.3% of the new listing this week, and fresh stock arriving unevenly tends to push spreads wider. For buyers the advice is simple. If a stone is listed in more than one place, check every listing before you commit. Right now that comparison could easily save you more than half the price. And if you've been looking at pears, they're cheaper than they were a week ago.

Diamond Market Charts, Week 42, 2026 (12 to 19 October 2026)

The five charts below summarise what the diamond market did during 12 to 19 October 2026. Each is a static image you can save or share. Together they cover where prices sit today, how inventory is moving, the lab-grown versus natural mix, where retailers raised or cut prices, and how much the same stone can vary across competing sellers.

Lucy Market Index

Ten numbers I record every snapshot.

Versus Week 41, 2026

Biggest shape movers

Recent trends

How metrics are tracking across the recent window of snapshots.

How the Lucy Market Index has moved

By origin

Top shapes by new listings

Notable stones

Each stone links to its full Carat Hunter listing.