Diamond Market, Week 19, 2026

Lab-grown supply flooded in this week. 1.15 million new lab-grown listings hit the market, up 63.6% on the prior week, and the median price per carat for those stones collapsed to $448, down a staggering 34.9% from $688 just seven days earlier. That's the single largest weekly move I've tracked in lab-grown pricing, and it dragged the overall market's total inventory value down to $83 billion, a record low across my seven week window. The stones are getting cheaper faster than they're accumulating.

Active inventory dipped below 25.4 million for the first time in this tracking window, sitting at a record low despite the surge in new listings. The explanation is straightforward: removals outpaced additions again, with 1.73 million stones leaving the market versus 1.53 million arriving. Natural diamonds bled inventory quietly, with 545,869 going off market against only 381,223 new listings. That's a net contraction of roughly 165,000 natural stones in a single week, and new natural supply was down nearly 20% on the prior period. Median natural price slipped 6% to $1,523, while price per carat eased to $2,296.

Lab-grown's share of active inventory reached a new high of 66%, ticking past 65.9%. It's been hovering in the 64.9 to 65.9% band for weeks, so this is a modest breakout rather than a sudden shift. But combined with the volume surge and price compression, it tells a clear story: producers are pushing more stones into the channel at ever lower price points, and retailers are absorbing (and rotating) them quickly. The 1.19 million lab-grown removals suggest demand isn't collapsing; it's just that supply is expanding faster than the market can hold price.

Cross-retailer overlap hit a record high of 50.3%, up from 46.9% last week. More than half the stones I'm tracking now appear across multiple retailers simultaneously. The median spread on those shared stones sits at 85.8%, meaning a buyer can find price differences of nearly 86% on the same diamond depending on where they look. That's enormous, and it hasn't compressed meaningfully even as overlap grows. For buyers, the implication is blunt: comparison shopping isn't optional, it's the difference between a fair deal and an overpay.

Shape movements were notable. Cushion and radiant took sharp hits, with median listing prices down 35.8% and 35.5% respectively. Cushion dropped to $1,108, radiant to $1,062. Both are popular lab-grown cuts, and the pricing reset likely reflects the broader lab-grown compression filtering through. On the other side, asscher and heart shapes climbed around 9% each, asscher reaching a median of $2,483. These are lower volume cuts (26,000 and 42,600 new listings respectively) where natural stones still dominate, so they're somewhat insulated from the lab-grown price reset. Rounds continued to own the volume story at 41.3% of all new listings.

Going into week 20, I'm watching whether lab-grown price per carat stabilises near $448 or continues to slide. The supply surge looks deliberate rather than seasonal, given the 63% jump, and if another wave arrives at these levels, sub-$400 per carat medians for lab-grown aren't far off. For natural buyers, the quiet inventory drain and softening prices might actually present opportunity: fewer stones, less competition, and retailers potentially more willing to negotiate. For lab-grown buyers, patience is paying off week after week.

Diamond Market Charts, Week 19, 2026 (4 to 11 May 2026)

The five charts below summarise what the diamond market did during 4 to 11 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 18, 2026

Biggest shape movers

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.