An Australian mining firm said Monday that it found the largest diamond ever to be dug up in the southern African nation of Angola. The gemstone weighs a whopping 404.2 carats.

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Lucapa Diamond Company, which discovered the 7-centimeter-long diamond in the northeastern Angolan province of Lunda Norte, said the diamond is the biggest ever to be recovered by an Australian company. The 2.75-inch jewel is about the length of a credit card.

“We’re not used to valuing 400-carat diamonds,” Miles Kennedy, Lucapa’s chairman told the Australian Broadcasting Corporation, “but if we look at other diamonds slightly less weight than this, you’re looking in the order of $20 million.”

The diamond is the world’s 27th largest, according to Lucapa, citing data available on Wikipedia. The previous record-setter for largest diamond discovered in Angola—the so-called Angolan Star—is almost half as massive at 217.4 carats. Last November, a different mining company, Lucara, recovered a 1,111 carat diamond in Botswana.

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Lucapa, based in West Perth, owns a 40% stake in Lulo, the mining project responsible for the find. Angola’s national diamond company Endiama owns 32% stake and a private local firm Rosas y Pétalas owns 28% stake in the project.

Mining operations began at the site last year. Kennedy told ABC that he plans to sell the diamond to fund an expansion in the area.