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5 Facts About the Largest Known Lab-Grown Diamond

It’s official: the biggest lab-grown rough diamond on record is blue—and British.


Lab-gemstone producer Meylor Global, based in the U.K., recently announced that it’s grown a blue diamond that the International Gemological Institute (IGI) independently weighed at 150.42 cts. and measured at 28.55 x 28.25 x 22.53 mm. The bodaciously big gem is thought to be the heaviest rough diamond crystal ever to be grown in a laboratory.


largest lab grown diamonds

The largest known lab-grown rough diamond (left), weighing 150.42 cts., and the second-largest (right), which is 141.58 cts. (courtesy of Meylor Global)

Here’s the 411 on the big blue (which has yet to be named) and the company that produced it:


  • Both the 150.42 ct. diamond and a second gray diamond weighing 141.58 cts. and measuring 28.90 x 28.50 x 20.75 mm (analyzed by IGI at the same time) surpassed the standing record for heaviest known rough lab-grown diamond: a 115 ct. rough crowned in September 2020, also grown by Meylor Global.


  • Most U.S. lab-grown diamond producers use the CVD, not the HPHT process, presumably because it’s cheaper. Natural diamonds are created from carbon crystallized through intense heat and pressure deep in the Earth, and according to the Gemological Institute of America (GIA), the HPHT mimics that process, “which is very costly given the energy and equipment required.” The CVD method is less expensive because it “works at moderate temperatures and low pressure, which requires smaller and less expensive equipment.” Which process produces better-quality and/or bigger diamonds is still under debate.


  • The diamonds are type IIb crystals, a semiconducting category associated with diamond-based electronics, according to IGI. Type IIb diamonds make up about 0.1% of all natural diamonds, making them one of the rarest and most valuable natural diamonds.


  • Meylor Global exclusively uses HPHT process, and the bulk of its gems are jewelry-quality polished diamonds represented from 0.01 to 20.00 cts. Maylor Global CEO Yuliya Kusher told JCK last year that the company was working on a (gulp) 200 ct. diamond. —Emili Vesilind


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