How much does a 3.00 to 4.99ct I SI2 natural marquise diamond cost?

As of September 2026, 3.00 to 4.99ct I SI2 natural marquise diamonds typically cost £12,670 GBP to £45,112 GBP, with a median price of £27,187 GBP. There are currently 91 diamonds matching this specification available across retailers.

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

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3.00 to 4.99ct I SI2 Natural Marquise

Quick answer

As of September 2026, there are 91 natural marquise diamonds with I colour and SI2 clarity in the 3.00 to 4.99ct range available across retailers worldwide. Prices typically run £12,670 GBP to £45,112 GBP, with a median of £27,187 GBP. At least 42 retailers stock this exact specification. Half of all listings fall between £6,088 GBP and £10,048 GBP per carat. The same specification in lab grown form lists at a median of about £5,463 GBP per carat.

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

Caratlytics Diamond Price Index, August 2026: natural diamonds at 2,184 USD per carat and lab-grown at 464 USD per carat, a natural to lab ratio of 4.7 to 1. Marquise natural stones in the index: 2,114 USD per carat, -8.8% month on month. See the full index release

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

Last updated: September 2026

Available

Lowest Price

£11,246 GBP

Highest Price

£96,923 GBP

Average Price

£27,773 GBP

Market Intelligence

Retailers Selling

Price Spread

47.9%

Price Range

Price per carat distribution across retailers

$10,509/ct

10th Percentile

$6,304

Median

$10,509

90th Percentile

$14,413

Score Distribution

91 diamonds scored across 4 quality tiers

Excellent

14 (15.4%)

Very Good

37 (40.7%)

Good

18 (19.8%)

Average

22 (24.2%)

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Consider Instead

Save money without compromising on what matters. These alternatives are visually similar but cost less.

J SI2J colour is visually identical to I to the naked eye

Save 46%

Lab-Grown I SI2Same specifications, lab-grown origin

Save 34%

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