StoneAlgo index reveals per-carat diamond price swings reshaping personalized jewelry

StoneAlgo's public snapshot shows a one-month drop in its 1 Carat Diamond Prices of -5.61 percent to $4,106, even as the same StoneAlgo page lists a round 1 ct per-carat price of $4,850. The page header reads "Diamond Price Snapshot as of 02/16/2026" while a page-level note records a snapshot dated 2026-02-17, a timestamp discrepancy that matters when pricing custom engagement rings and bespoke pendants.

StoneAlgo's shape table lists per-carat retail medians across 0.5 to 3 carat bands: round 1 ct $4,850, oval 1 ct $3,896, and pear 1 ct $4,384. Category-level medians show colorless 1 ct at $5,170 versus included 1 ct at $3,274. StoneAlgo also publishes larger-size headline metrics: 2 Carat Diamond Prices are down 3.39 percent month-on-month at $18,866 with inventory 40.4K and Inv. Change 3.32K; 3 Carat Diamond Prices are down 2.88 percent at $43,825 with inventory 13.8K and Inv. Change 630. The page contains two inventory-change lines—one reads "Inv. Change : 11.8K" near the 1 ct block and another line shows "Inv. Change : 12.3K"—both appear on the page as presented.

Pricescope's grade-level snapshot offers a different angle on buyer behavior. "J SI1 held steady at $2,175, unchanged from January" while "J VS2 increased slightly to $2,566 from $2,558" and "K SI2 rose marginally to $1,982 from $1,970, maintaining a narrow trading range." Pricescope summarizes that "Several categories showed mild firmness. I SI1 increased to $3,051 from $2,719, while K VS1 held near flat at $3,483 versus $3,493. These movements suggest continued transactional activity among value-focused buyers seeking balance between cost and acceptable visual standards." Pricescope also reports shape-share movement: "Cushion diamonds move into second position at 7.30%, up from 6.90% month over month" and "Oval diamonds follow closely at 7.07%, remaining effectively stable."

CaratX situates those shifts within broader market momentum. In a Feb, 04, 2026 analysis by Archit Mohanty, CaratX reports that "The most recent data from the RapNet Diamond Index (RAPI™) ... fell by a modest 1.3% in January for both 0.30-carat and 1-carat diamonds," and that this "follows steeper declines of 6.3% and 4.7% respectively in the previous two months," suggesting the pace of declines eased going into February.

IDEX's Diamond Index adds microstructure detail. Its top driver is "Round, 4/4 (1.00-1.49), D-K, IF-I1" representing 12.06 percent of the market with a current average asking price of 3175.11 and index 64.36 with percent change 0.17. By contrast, larger stones show volatility: "Round, 3.00 (3.00-3.49), D-J, IF-SI2" lists a current average asking price of 16182.57 and a percent-change of -0.62. IDEX notes that its index was developed "in cooperation with Dr. Avi Wohl, Senior Lecturer of Finance at the Faculty of Management, Tel Aviv University," and that "The diamond index is updated every hour."

For makers and buyers of personalized jewelry, these numbers matter in specific ways: StoneAlgo's colorless 1 ct median at $5,170 versus included 1 ct at $3,274 signals a wide grade premium, while Pricescope's "E-grade premiums remained comparatively stable" with "E FL held effectively flat at $11,927 versus $11,926." The immediate spread between StoneAlgo's round 1 ct at $4,850 and its 1 ct index at $4,106 is $744 per carat, a shareable pricing nugget to use in negotiations.

Before setting retail prices or sourcing stones, verify the StoneAlgo timestamp (02/16/2026 header vs 2026-02-17 page snapshot), ask StoneAlgo to clarify the difference between its shape-level prices and the 1 ct index, and check CaratX's RapNet citation which lists a conflicting date. Have you sold a similar piece recently? Tell us what you got.