Diamond Market, Week 21, 2026

A 35% surge in new listings defined week 21. Over 1.53 million stones entered the market, up from 1.14 million the prior week, while only 310,000 left. That imbalance pushed active inventory to 28.2 million, a seven week high across the retailers I track. The maths is straightforward: supply is stacking up, and the market hasn't absorbed it yet.

Prices reflected the glut. Median price per carat slid to $940.95, down 4.6% week on week and its lowest point in the seven week window I'm watching. The headline median price barely moved at $1,070, essentially flat, but the per carat figure tells the real story. Stones are getting listed at lower per carat asks, particularly on the lab-grown side, where median price per carat fell a sharp 24% to $464. Natural per carat pricing held steadier at $2,098, up fractionally, though natural median total price still dropped 6.8% to $1,151. Both origins saw softer pricing; the scale of the lab-grown correction is what stands out.

Cross-retailer spread compressed to 84.8%, down from 90.4% the prior week. That's a seven week low. When the same stone appears across multiple retailers, the gap between the cheapest and most expensive offer is narrowing. For buyers, this is solid news: less pricing dispersion means less risk of overpaying, and it suggests competitive pressure is doing its job. Overlap itself ticked up to 50.5%, also a seven week high, so more stones are appearing across multiple shopfronts simultaneously. The market is getting more transparent, even if it isn't getting cheaper.

Princess and cushion cuts had a strong week. Princess median price climbed 11.3% to $1,172, while cushion jumped 10% to $1,470. Pear also edged up 4.7% to $1,005. On the other side, heart shaped stones dropped 27.5% and the niche categories saw steep median price falls, though volumes there are small enough that a handful of listings can swing the number. Rounds continued to dominate new supply at 42% of all fresh listings, with a median of $818.

Lab-grown share dipped slightly to 64.8%, its lowest in seven weeks, though still firmly the majority of inventory. Natural stones saw a notable supply push of their own: 514,000 new natural listings, up 38.5% from the prior week. But natural removals dropped 55%, meaning far fewer natural stones left the market. The pattern is consistent across both origins. Sellers are adding. Buyers aren't clearing at the same pace.

The combination to watch going into week 22 is whether this inventory build triggers further price softening or whether buyers step in at these lower per carat levels. Spread compression suggests the market is getting more efficient, but the sheer volume of unsold stock (nearly 28.25 million stones) creates downward pressure. Budget-conscious buyers looking at lab-grown rounds or ovals in the 1 to 1.5ct range won't find a better moment to compare across the retailers I follow. If removals don't pick up soon, expect further per carat erosion, particularly in lab-grown.

Diamond Market Charts, Week 21, 2026 (18 to 25 May 2026)

The five charts below summarise what the diamond market did during 18 to 25 May 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 20, 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.