Synthetic diamond technology appears to be progressing quickly, with yet another lab-grown stone being labelled the “world’s largest”.

The claim, made by the International Gemological Institute (IGI) Hong Kong branch, refers to a 10.02-carat square emerald cut diamond. The laboratory certified the type IIa stone as having VS1 clarity and E colour with a “very good to excellent” finish grade.

The diamond originated from a 32.26-carat piece of rough produced by Russian synthetic diamond manufacturer New Diamond Technology (NDT) using the HPHT (high pressure, high temperature) technique. It was said to have taken less than 300 hours to grow.

IGI Worldwide co-CEO Marc Brauner described the diamond as “unique in all aspects”, adding that the science and technology used to produce the stone was “significantly more advanced than other man-made diamonds currently on the market”.

In evidence of the rate at which the synthetic diamond sector is progressing, this latest diamond was almost double the size of the HPHT synthetic stone – dubbed ‘Big Tamazi’ – that NDT claimed was the world’s largest polished diamond in February this year.

The radiant cut stone, which had also been a type IIa diamond, weighed 5.11 carats with K colour and SI2 clarity and had been derived from a 10.31-carat piece of rough.

Only a few months before, US-based Pure Grown Diamonds also made a “world’s largest” claim about a near colourless, 3.04-carat round stone with I colour, SI1 clarity and a “very good cut”. Pure Grown Diamonds, however, used a different process – CVP (chemical vapour deposition) – to grow the stones.

The most recent record-breaking diamond was said to be on display at the NDT booth during the 2015 JCK Las Vegas jewellery trade show, held from Friday 29 May to Monday 1 June.