RAPI 1-carat adds 0.59% since 8 August, now published daily
Rapaport's index page now carries a dated level for every day of a 30-day window. The 0.50-carat leads at 2.38% and the 2-carat is the only faller, down 0.25%.
By The Diamonds Desk
What changed
The index turns daily. Rapaport's diamond index now carries a dated level for every day of a trailing 30-day window, where it published monthly points a week ago. The 1-carat reads $3,901.76 at 6 September.
What it means
- If you price off RAPI: date the mark to 6 September, not to a month. The level now moves daily.
- If you hold 2-carat goods: yours is the only size lower over the window, by 0.25%.
- What this is not: a new price. The same asking prices are simply dated more often.
Key figures
| 1-carat leveldated 6 September | $3,901.76 |
|---|---|
| 0.50-caratthe window's best size | +2.38% |
| 0.30-caratsecond over the window | +1.80% |
| 2-caratthe only size lower | −0.25% |
Source: Rapaport Trade Diamond Index · daily series, 8 August to 6 September 2026 · read 7 September 2026
The series is dated daily
Thirty points, not one. The page carries a dated level for every day from 8 August to 6 September, for each of five sizes. A week ago it carried one point a month.
The lag is a session. The newest point is dated 6 September and was read on 7 September. Rapaport's monthly series reported August's move in the first week of September.
| Size | Level, 6 Sep | Window change | Day on day |
|---|---|---|---|
| 0.30-carat | $935.10 | +1.80% | +$0.36 |
| 0.50-carat | $1,287.73 | +2.38% | +$0.76 |
| 1-carat | $3,901.76 | +0.59% | +$2.71 |
| 2-carat | $10,630.33 | −0.25% | +$3.20 |
| 3-carat | $17,881.15 | +0.14% | −$37.50 |
Source. Rapaport's index page, read 7 September 2026.
Window. is the page's own 30-day series, 8 August to 6 September.
Day on day. is Carat Capital's difference between the two newest daily points.
Small goods lead the window
Half-carat best at 2.38%. The 0.50-carat gained 2.38% across the window and the 0.30-carat 1.80%, against 0.59% for the 1-carat.
Only the 2-carat fell. The 2-carat is down 0.25% across the window at $10,630.33, although it has risen at each of its last three daily points.
It agrees with August
Same direction, finer grain. Rapaport's August monthly reading put the 1-carat up 0.5%, its first rise in fifteen months, with every smaller size up more. The daily window says the same thing one day at a time.
What to watch
- 8 SepThe next daily point, and whether the 3-carat takes back its $37.50.
- SepJewellery & Gem World, Hong Kong, where asking prices meet order books.
- Early OctRapaport's September summary, against this window's +0.59% on the 1-carat.
The story so far
- Half a percent after fifteen monthsAugust monthly RAPI put the 1-carat up 0.5%.
- Six seventy-five and a rising indexLab-grown at $675 while the natural index rose.
- The 1-carat stops fallingJuly flat, every other size up.
Go deeper
What would change this call
A run of daily points in which the 0.30 and 0.50-carat give back the window's gains while the 1-carat holds. That would make the small-size lead a summer artifact and send pricing back to the monthly reading.
How RAPI is built
The Rapaport Trade Diamond Index tracks asking prices, not settled trades. For each of the top 25 quality categories of round diamonds listed on Rapaport Trade, the marketplace formerly called RapNet, it averages the asking prices of the cheapest tenth of stones. The headline series are D to H colour, IF to VS2 clarity, at 0.30, 0.50, 1, 2 and 3 carats.
Method
Rapaport's index page embeds its series as a JSON block carrying a from and to date and, for each size, a dated price for every day in the window. Read on 7 September 2026 the window runs 8 August to 6 September, thirty points a size. The window change printed above is the first-to-last move computed by Carat Capital: the 0.30-carat from $918.57 to $935.10 is +1.80%, the 0.50-carat from $1,257.79 to $1,287.73 is +2.38%, the 1-carat from $3,878.88 to $3,901.76 is +0.59%, the 2-carat from $10,656.97 to $10,630.33 is −0.25%, the 3-carat from $17,856.15 to $17,881.15 is +0.14%. Each reconciles to the page's own printed change for that size, which had not previously been reconciled and is now established as a window figure. Day-on-day differences subtract the 5 September point from the 6 September point. Carat Capital's natural diamond price list carries the 1-carat RAPI as a July 2026 point and does not yet reflect this series.