How much does a 1.50 to 1.99ct I SI2 natural marquise diamond cost?

As of October 2026, 1.50 to 1.99ct I SI2 natural marquise diamonds typically cost £2,250 GBP to £12,402 GBP, with a median price of £5,003 GBP. There are currently 212 diamonds matching this specification available across retailers.

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

About 40% of these diamonds are available at multiple retailers, with an average price spread of 58%. A comparison tool like Carat Hunter lets you see all the prices side by side.

1.50 to 1.99ct I SI2 Natural Marquise

Quick answer

As of October 2026, there are 212 natural marquise diamonds with I colour and SI2 clarity in the 1.50 to 1.99ct range available across retailers worldwide. Prices typically run £2,250 GBP to £12,402 GBP, with a median of £5,003 GBP. At least 52 retailers stock this exact specification, and 40% of the stones appear at more than one of them, with an average price spread of 58%. Half of all listings fall between £2,386 GBP and £4,410 GBP per carat. The same specification in lab grown form lists at a median of about £1,023 GBP per carat. Over the last 30 days the median price moved -4.3% and the number of listings moved +18.4%.

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

Caratlytics Diamond Price Index, September 2026: natural diamonds at 2,335 USD per carat and lab-grown at 443 USD per carat, a natural to lab ratio of 5.3 to 1. Marquise natural stones in the index: 2,268 USD per carat, +10.8% 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: October 2026

Available

212

Lowest Price

£1,293 GBP

Highest Price

£20,526 GBP

Average Price

£5,930 GBP

Market Intelligence

Retailers Selling

Cross Retailer %

39.6%

Price Spread

57.8%

30-Day Price Trend

-4.3%

30-Day Supply Change

+18.4%

Volatility (30d)

0.01

Price Range

Price per carat distribution across retailers

$4,694/ct

10th Percentile

$2,447

Median

$4,694

90th Percentile

$7,521

Score Distribution

504 diamonds scored across 4 quality tiers

Excellent

100 (19.8%)

Very Good

145 (28.8%)

Good

98 (19.4%)

Average

161 (31.9%)

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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 21%

Lab-Grown I SI2Same specifications, lab-grown origin

Save 71%

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