CaratRings.com puts the lab-grown 1-carat median back at $571
The September edition read 251,098 listings at seven US retailers on 17 September. Ritani raised its one-carat asking median 26% while Brilliant Earth cut its 1.5-carat cell 32%.
The median is published again. Rings.com's September index puts the one-carat lab-grown market median at $571 a carat. It is the first one-carat median the index has published since June.
If you price lab-grown at retail: Four US counters now quote between $281 and $796 for the same one-carat spec.
If you restock lab-grown goods: Ritani reversed August's cuts at all three weights. Brilliant Earth moved the other way.
What this is not: A wholesale price. These are listed asking prices, not transactions.
| Retailer | 1ct median | Change on August |
|---|---|---|
| Ritani | $281 | +26% |
| Grown Brilliance | $500 | 0% |
| With Clarity | $642 | not published |
| Brilliant Earth | $796 | -7% |
| Market median | $571 | first since June |
ITwo counters moved, two did not
Ritani reversed course. Its one-carat median rose from $223 to $281 a carat, up 26%, the opposite direction from August's cut across the same cells.
Brilliant Earth cut. Its 1.5-carat median fell 32%, from $1,151 to $784 a carat, the largest single-cell move on the panel this edition.
Grown Brilliance held. All three of its cells moved by 3% or less while its listed one-carat inventory fell from 795 stones to 435.
IIWhy two weights stay withheld
The rule is composition. The index withholds a blended median when the contributing retailers change, so the figure measures prices rather than who is in the panel.
One carat passes. The same four retailers published a one-carat figure in August and September, so the eligibility test clears and the median is republished.
The other two fail. Blue Nile's newly published 1.5-carat and 2-carat cells, and Clean Origin's 1.5-carat cell, were not in August's contributor set.
IIIListings, not transactions
The basis matters. Every figure is a publicly visible list price at the moment of collection, including automatic site-wide reductions but excluding promotional codes.
The sample is large. 251,098 listings across seven retailers were read on 17 September, and the next edition is due the week of 26 October.
01What would change this call+
A month in which the four contributing retailers change again. The median is withheld whenever the contributor set moves, which is why it went unpublished in July and August; one seller thinning at one carat takes the figure off the page regardless of where prices go.
02How this median is built+
The index reads publicly visible list prices for a fixed specification, a one-carat E VS1 round excellent stone graded by IGI, at a fixed panel of seven United States online sellers. A retailer's cell publishes only if at least 30 listings clear the specification; below that the cell is shown as thin and left blank. The blended market median is then taken across the sellers that published, but only when the same sellers published in the prior edition as well. That last test is why a figure can vanish for two months while every underlying price is still being collected: the rule is protecting against a median that measures panel composition instead of price.
03Method · the desk’s arithmetic+
The September 2026 edition was fetched directly on 21 September 2026 and read for each figure printed here rather than for a summary. The page's own dateModified and last_updated fields both read 2026-09-18, and its methodology section states the collection date as 17 September 2026. Every figure above appears in the source's own text: the $571 market median and the description of it as the first published since June; the $281 to $796 range across four IGI-panel retailers; the 251,098 listings across seven retailers; Ritani's one-carat move from $223 to $281 and its 1.5-carat and 2-carat moves; Brilliant Earth's 1.5-carat fall from $1,151 to $784 and its one-carat move from $856 to $796; Grown Brilliance's one-carat sample falling from 795 stones to 435 at an unchanged $500; and With Clarity's one-carat figure of $642 on 453 listings. Two figures here are Carat Capital's own division and are labelled as such in the table note: 796 ÷ 281 = 2.83 and 856 ÷ 223 = 3.84. With Clarity's August one-carat median is not stated anywhere in the source, so no change is printed for that row rather than a change being reconstructed. The main table's columns are total stone price; at one carat the total and the per-carat figure are the same number, which is why the one-carat column is used and the heavier columns are not. ARCHIVE: the Rings.com Lab-Grown Diamond Price Index - greps of content/articles.json for 'Rings.com', '251,098', 'Grown Brilliance', 'With Clarity' and 'market median' returned zero hits in 404 articles; the only place the name appears anywhere on this site is the standing lab-grown price list page, which is a data page and not an article. NEW, and this is the first edition of this index the paper has written up.
RAPI's 1-carat holds at $3,912.13 for a fifth morning
The natural counter on the same morning, unmoved for five days.
The trade, filed before the New York open.
Prices, tenders and the one story that moved the industry overnight. Ninety seconds.
Subscribe free →