CaratRAPI's 1-carat holds at $3,912.13 for a fifth morning
The index has posted no new point since 16 September, though it moved to daily publication on 7 September. IDEX's broad one-carat driver averaged $3,051.17 on the same morning, 22.0% below it.
The one-carat stopped moving. RapNet's one-carat index has carried $3,912.13 since 16 September, its newest published point, with no new print in the five mornings since.
If you buy one-carat polished: The benchmark has not moved in five days. The broad counter sits 22.0% under it.
If you quote off RAPI: Your reference is five days old. Check the date on the point, not the day you read it.
What this is not: A frozen market. The index has not printed, not the same thing.
| Weight | RAPI | IDEX | Gap |
|---|---|---|---|
| 0.50 carat | $1,315 | $1,379 | +4.8% |
| 1.00 carat | $3,912 | $3,051 | -22.0% |
| 3.00 carat | $18,024 | $16,224 | -10.0% |
IThe index went quiet
Five mornings, one level. RapNet's one-carat index has carried $3,912.13 on every morning since 17 September, its source not having published a newer point.
Daily was the promise. The index moved from monthly to daily publication on 7 September. It has printed no new point in the five days since 16 September.
IIThe broad counter sits lower
Two numbers, one carat. IDEX's price-driver average for a one-carat round read $3,051.17, against RAPI's $3,912.13, a gap of 22.0%.
The gap inverts. At half a carat the broad counter sits above the narrow one, $1,379 against $1,315, a gap of 4.8% the other way.
IIILab-grown moved the same week
The other counter repriced. A lab-grown retail index published on 18 September reset its one-carat median to $571, while the natural benchmark stood still.
01What would change this call+
A new RAPI point. The level here is not a market judgement, it is the absence of a fresh print; one new daily point ends the story whichever way it goes.
02Why two indices disagree by a fifth+
RAPI is the average asking price of the ten per cent lowest-priced stones on RapNet within a narrow band, D to H colour and IF to VS2 clarity, GIA graded. It is a floor for a top specification rather than a market mean. IDEX price drivers average a far broader spread of colour and clarity, D to K and IF to I1 at one carat, and weight each driver by its share of the market. A broad average of an inclusive band will sit below a floor for a narrow one, which is what the one-carat row shows. At half a carat the relationship inverts because the two bands overlap differently at that weight. Neither is wrong; a single diamond price does not exist.
03Method · the desk’s arithmetic+
RAPI's level was read from the tape's own dated files rather than from prose, and the hold was counted from entries rather than described: the mark $3,912.13 with sourceDate 2026-09-16 appears in newsroom/tape/2026-09-17.json, 09-18, 09-19, 09-20 and 09-21, five entries, which is what 'five mornings' means here. The source's own newest point is dated 16 September and has not advanced. IDEX's index page was fetched directly on 21 September and its first price driver, Round 4/4 (1.00-1.49) D-K IF-I1 at 12.06% of market, was read from the page's own table; it showed $3,055.60 at 06:15 ET against the $3,051.17 the price list carries from the 05:00 read, because the page states the index updates hourly. The 05:00 figure is printed because it is the one the paper's own record carries for today; the press-time re-read is disclosed in the table note rather than substituted. The gap column is Carat Capital's division and is printed in full in the table note so it can be checked. The 0.50 and 3.00 carat rows are carried from the price list's dual-basis table, which was refreshed from the same IDEX fetch this morning. ARCHIVE: RAPI and the one-carat polished benchmark - ours of 2026-09-07 covers the index's move to daily publication and the 0.59% gain from 8 August to 6 September; ours of 2026-09-03 covers the August monthly reading of +0.5%. This item covers 16 to 21 September 2026, a period neither of them reaches, and its subject is the absence of a new print rather than a move. SAME ENTITY, LATER AND DIFFERENT PERIOD, so ADVANCED, not a repeat.
RAPI 1-carat adds 0.59% since 8 August, now published daily
The 7 September switch to daily publication, and what it was meant to fix.
The trade, filed before the New York open.
Prices, tenders and the one story that moved the industry overnight. Ninety seconds.
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