How much does a 0.50 to 0.74ct I SI1 lab grown cushion diamond cost?

As of October 2026, 0.50 to 0.74ct I SI1 lab grown cushion diamonds typically cost £403 GBP to £663 GBP, with a median price of £533 GBP. There are currently 1 diamonds matching this specification available across retailers.

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

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0.50 to 0.74ct I SI1 Lab Grown Cushion

Quick answer

As of October 2026, there are 1 lab grown cushion diamonds with I colour and SI1 clarity in the 0.50 to 0.74ct range available across retailers worldwide. Prices typically run £403 GBP to £663 GBP, with a median of £533 GBP. The same specification in natural form lists at a median of about £846 GBP per carat.

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

0.71ct Cushion I SI1, IGI, grade B+, from £370 GBP

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. Cushion lab grown stones in the index: 516 USD per carat, +6.9% 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

Lowest Price

£370 GBP

Highest Price

£695 GBP

Average Price

£533 GBP

Score Distribution

2 diamonds scored across 2 quality tiers

Very Good

1 (50.0%)

Average

1 (50.0%)

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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