How much does a 5.00ct+ I SI2 natural marquise diamond cost?

As of November 2026, 5.00ct+ I SI2 natural marquise diamonds typically cost £29,725 GBP to £88,479 GBP, with a median price of £53,724 GBP. There are currently 12 diamonds matching this specification available across retailers.

Where can I find the best price on a I SI2 marquise diamond?

About 38% of these diamonds are available at multiple retailers, with an average price spread of 16%. A comparison tool like Carat Hunter lets you see all the prices side by side.

5.00ct+ I SI2 Natural Marquise

Quick answer

As of November 2026, there are 12 natural marquise diamonds with I colour and SI2 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run £29,725 GBP to £88,479 GBP, with a median of £53,724 GBP. At least 14 retailers stock this exact specification, and 38% of the stones appear at more than one of them, with an average price spread of 16%. Half of all listings fall between £10,774 GBP and £12,570 GBP per carat. Over the last 30 days the median price moved -2.6% and the number of listings moved +27.5%.

Three of the best scored stones at this specification right now:

Caratlytics Diamond Price Index, October 2026: natural diamonds at 2,202 USD per carat and lab-grown at 462 USD per carat, a natural to lab ratio of 4.8 to 1. Marquise natural stones in the index: 2,177 USD per carat, -4.2% month on month. See the full index release

Figures come from current listings across more than 100 retailers and refresh daily. The index is a monthly release.

Last updated: November 2026

Available

Lowest Price

£26,525 GBP

Highest Price

£190,431 GBP

Average Price

£61,681 GBP

Market Intelligence

Retailers Selling

Cross Retailer %

38.2%

Price Spread

15.7%

30-Day Price Trend

-2.6%

30-Day Supply Change

+27.5%

Volatility (30d)

0.01

Price Range

Price per carat distribution across retailers

$15,314/ct

10th Percentile

$14,239

Median

$15,314

90th Percentile

$18,564

Score Distribution

22 diamonds scored across 4 quality tiers

Excellent

4 (18.2%)

Very Good

7 (31.8%)

Good

8 (36.4%)

Average

3 (13.6%)

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Related Specifications

D IF D VVS1 D VVS2 D VS1 D VS2 D SI1 E IF E VVS1 E VVS2 E VS1 E VS2 E SI1 F IF F VVS1 F VVS2 F VS1 F VS2 F SI1 G IF G VVS1 G VVS2 G VS1 G VS2 G SI1 H IF H VVS1 H VVS2 H VS1 H VS2 H SI1 I IF I VVS1 I VVS2 I VS1 I VS2 I SI1