How much does a 5.00ct+ I SI1 lab grown marquise diamond cost?

As of November 2026, 5.00ct+ I SI1 lab grown marquise diamonds typically cost £2,365 GBP to £2,365 GBP, with a median price of £2,365 GBP. There are currently 1 diamonds matching this specification available across retailers.

Where can I find the best price on a I SI1 marquise diamond?

About 22% of these diamonds are available at multiple retailers, with an average price spread of 52%. A comparison tool like Carat Hunter lets you see all the prices side by side.

5.00ct+ I SI1 Lab Grown Marquise

Quick answer

As of November 2026, there are 1 lab grown marquise diamonds with I colour and SI1 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run £2,365 GBP to £2,365 GBP, with a median of £2,365 GBP. At least 13 retailers stock this exact specification, and 22% of the stones appear at more than one of them, with an average price spread of 52%. Half of all listings fall between £214 GBP and £394 GBP per carat.

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

8.18ct Marquise I SI1, IGI, grade B, from £2,365 GBP

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 lab grown stones in the index: 505 USD per carat, +1.6% 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

£2,365 GBP

Highest Price

£2,365 GBP

Average Price

£2,365 GBP

Market Intelligence

Retailers Selling

Cross Retailer %

22.2%

Price Spread

51.6%

Price Range

Price per carat distribution across retailers

$469/ct

10th Percentile

$135

Median

$469

90th Percentile

$808

Score Distribution

1 diamonds scored across 1 quality tiers

Good

1 (100.0%)

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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