Diamond Market, Week 37, 2026

Lab-grown's share of active inventory has slipped to 61.9%, the lowest reading across the six weeks I've been tracking. That's down from a 64.9% peak in week 31, and the slide has now run six consecutive weeks without a recovery. Meanwhile new listings hit a record for the same stretch at 2.4 million for the week, the highest weekly inflow I've seen. More supply is arriving, but a greater proportion of it is natural. Whether that reflects deliberate sourcing shifts from the retailers I track or simply natural inventory cycling through at pace, the direction is consistent.

The spread story has moved in parallel. The median cross-retailer price spread compressed to 71.9%, its lowest point across the six weeks on record, down from a peak of 81.8% just three weeks ago. Cross-retailer overlap fell to 44.5% at the same time, also a record low for the window. Those two signals together suggest the surge in new listings is bringing in inventory that fewer retailers share in common. As differentiation increases, the gap between prices for the same stone listed across multiple retailers has narrowed. A handful of names did most of the listing this week, accounting for 43.5% of new stock between them.

Median active inventory size has drifted to 1.2 carats, matching the lowest reading across the window and down from 1.31ct at the peak in week 32. Median price has followed, falling to $1,061, the lowest across five periods and down 7.1% from $1,141 in week 31. Price per carat has softened too, off 2.2% over the window to around $931. None of this signals distress; it reads more like a gradual weight shift toward smaller, more accessible stones, possibly reflecting where buyer demand sits as the final quarter approaches.

At the top of the market, the week's most expensive stone was a 20.28ct natural round brilliant, E VVS1, GIA certified, listed at $2,673,096. The largest stone I tracked was a 62.96ct lab-grown emerald cut, E VVS1, IGI certified, at $234,619. And for anyone who assumes lab-grown means budget-conscious, three IGI certified lab-grown stones cleared $1.9 million this week, among them a 10.07ct heart shape at $2,183,610. The top end of the market has no shortage of lab-grown representation.

Heading into week 38, the question I'm carrying is whether lab-grown's share stabilises or keeps sliding. Six weeks of falling share is a genuine trend. If cross-retailer overlap continues compressing while new listings stay elevated, buyers shopping across multiple retailers will find less duplication and, potentially, less room to negotiate on price. The spread has already narrowed considerably. Active inventory is at a record for the tracking window, so supply isn't tight, but its composition is shifting. That's the read I'll be bringing to next week.

Diamond Market Charts, Week 37, 2026 (7 to 14 September 2026)

The five charts below summarise what the diamond market did during 7 to 14 September 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 36, 2026

Recent trends

How metrics are tracking across the recent window of snapshots.

How the Lucy Market Index has moved

Notable stones

Each stone links to its full Carat Hunter listing.