A 55.22-carat ruby is poised to become the largest — and should it sell for over US$30.3 million, the most valuable — gem of its kind ever to appear at auction.

The stone is set to go under the hammer in New York in June, less than a year after Canadian firm Fura Gems discovered it at one of its mines in Mozambique.

Announcing the sale Wednesday,  Sotheby's described the jewel as "exceedingly rare" and "the most valuable and important" ruby ever to come to market. Named Estrela de Fura (or Star of Fura in Mozambique's official language, Portuguese), the stone is expected to fetch "in excess of" US$30 million, the auction house said.

Although record gemstone sales are dominated by diamonds — colored ones, in particular — rubies are also considered among the world's rarest and most valuable gemstones. The current auction record for a ruby was set by the Sunrise Ruby, a 25.59-carat stone found in Myanmar that fetched $30.3 million in Geneva, Switzerland, in 2015.

Estrela de Fura was cut from a rough stone that made headlines when it was unearthed by miners last July. Originally weighing 101 carats, almost twice as much as in its current form, it was the largest gem-quality ruby ever discovered.

The huge stone was cut into a smaller symmetrical shape and polished, processes that remove impurities and enhance the color and brilliance of a gemstone before it is put onto the market. According to Sotheby's, a report from the Swiss Gemmological Institute said that this had "resulted in vivid red hues due to multiple internal reflections."

In a statement, Fura Gems' founder and CEO, Dev Shetty, said stones of such size and quality are "almost unheard of."