( CNN) As the head of jewelry in Asia for British auction mansion Bonhams, Graeme Thompson is used to managing beautiful diamonds on a daily basis. Yet he’s only ever held a red diamond once, about five years ago. “Red diamonds are the rarest of them all and whoever gets to hold one in his hand is very lucky indeed, ” he said.

Fancy Red diamonds are on the pink diamond color spectrum and is a grading from the Gemological Institute of America.

On Wednesday in New York, Rio Tinto unveiled its largest Fancy Red diamond yet to a select group of collectors, alongside other gemstones in its annual tender of pink diamonds. Known as the Argyle Everglow, the refined radiant cut diamond weighs 2.11 carats.