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

As of November 2026, 5.00ct+ G SI1 lab grown marquise diamonds typically cost £485 GBP to £1,987 GBP, with a median price of £773 GBP. There are currently 17 diamonds matching this specification available across retailers.

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

About 40% of these diamonds are available at multiple retailers, with an average price spread of 111%. A comparison tool like Carat Hunter lets you see all the prices side by side.

5.00ct+ G SI1 Lab Grown Marquise

Quick answer

As of November 2026, there are 17 lab grown marquise diamonds with G colour and SI1 clarity in the 5.00ct+ range available across retailers worldwide. Prices typically run £485 GBP to £1,987 GBP, with a median of £773 GBP. At least 32 retailers stock this exact specification, and 40% of the stones appear at more than one of them, with an average price spread of 111%. Half of all listings fall between £158 GBP and £415 GBP per carat. The same specification in natural form lists at a median of about £14,888 GBP per carat. Over the last 30 days the median price moved -17.7% and the number of listings moved +36.5%.

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 lab grown stones in the index: 485 USD per carat, -3.2% 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

£419 GBP

Highest Price

£4,650 GBP

Average Price

£994 GBP

Market Intelligence

Retailers Selling

Cross Retailer %

40.3%

Price Spread

111.2%

30-Day Price Trend

-17.7%

30-Day Supply Change

+36.5%

Volatility (30d)

0.05

Price Range

Price per carat distribution across retailers

$310/ct

10th Percentile

$152

Median

$310

90th Percentile

$738

Score Distribution

22 diamonds scored across 4 quality tiers

Excellent

12 (54.5%)

Very Good

3 (13.6%)

Good

3 (13.6%)

Average

4 (18.2%)

Find Your Diamond

Search 17 G SI1 marquise diamonds and compare prices.

Search Diamonds

Consider Instead

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

G SI2SI2 inclusions are not visible without magnification

Save 24%

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