How much does a 3.00 to 4.99ct I SI1 natural marquise diamond cost?

As of September 2026, 3.00 to 4.99ct I SI1 natural marquise diamonds typically cost £16,417 GBP to £44,689 GBP, with a median price of £31,933 GBP. There are currently 52 diamonds matching this specification available across retailers.

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

Compare prices across retailers on Carat Hunter to see all your options.

3.00 to 4.99ct I SI1 Natural Marquise

Quick answer

As of September 2026, there are 52 natural marquise diamonds with I colour and SI1 clarity in the 3.00 to 4.99ct range available across retailers worldwide. Prices typically run £16,417 GBP to £44,689 GBP, with a median of £31,933 GBP. At least 44 retailers stock this exact specification. Half of all listings fall between £8,871 GBP and £12,287 GBP per carat. The same specification in lab grown form lists at a median of about £1,376 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

£12,755 GBP

Highest Price

£60,881 GBP

Average Price

£31,398 GBP