A ruby sold at Sotheby's in New York on Thursday for $34.8 million, setting a new record price at auction for the precious stone.

The 55.22-carat gemstone named Estrela de Fura was already the largest ruby ever to go under the hammer.

It was cut from a 101-carat rough stone discovered in July last year at the Montepeuz ruby mine in Mozambique operated by the Fura Gems company.

The stone was the star attraction of a sale offering 100 different pieces of jewelry.

Offered at a starting price of $21 million, it sold for $30 million plus fees and commissions to an anonymous telephone buyer.

The previous record belonged to a 25.59-carat Burmese ruby, which sold for a total price of $30.33 million by Sotheby's in Geneva in 2015.

"This is really a true wonder of nature," Quig Bruning, head of jewelry for Sotheby's in the Americas, told AFP.

"Any ruby that comes out of the ground that ends up over five carats as a polished ruby is something that's rare. Ten carats is really rare. Twenty carats is almost unheard of," he said.

"Any ruby really over 50 carats is a once-in-a-lifetime opportunity," Bruning added.

Sotheby's also sold "The Eternal Pink," a rare 10.57-carat diamond from a mine in Botswana, for the same price of $34.8 million.

That set a record per carat of $3.29 million for a stone of its color.

The most expensive pink diamond sold to date was the $71.2 million paid for the 59.60-carat "Pink Star" in Hong Kong in 2017.