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  (Photo: Twitter/NewsonGreen)
  The "Beau Sancy" will be auctioned on May 14 by Sotheby's.

Auction-house giant Sotheby's has been given a real gem to sell. A 400-year-old diamond with a colorful and royal past will soon be up for auction.

The "Beau Sancy" weighs in at 34.98 carats and is expected to bring in $4 million at its auction in Geneva on May 14. This gem has quite a history, one that is worth the money alone. According to the Associated Press, France's King Henri IV purchased the diamond from the Lord of Sancy as a gift for his wife, Marie de Medici.

When King Henri was assassinated in 1610, Marie acted in place of his heir, King Louis XIII. After political turmoil ensued, Marie found herself exiled to the Chateau de Blois; she fled Blois two years later and lived there the rest of her life in exile.

By the time she died, in 1642, she was remembered for her fall from glory rather than her riches and royal connections.

An essay by Catherine de Medici summed up Marie's tumultuous life.

"Marie de Medici never purged herself of the charge of having known of the king's assassination … she wasted the wealth amassed by King Henry IV. [Her] conduct was such that she forced her son to banish her from France," it read.

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Marie sold the diamond in an attempt to gain back a part of her fortune. It was then passed down through four royal European families, with its last owners being descendants of Germany's last emperor.

"It has a fascinating history, and really is a once-in-a-lifetime sale," David Bennett, Sotheby's jewelry chairman told the AP. "When it was made in the 16th century, the pear cut was new, bold, and so it became the most sought-after jewel of its era. Before the 'Beau Sancy,' all diamonds were rudimentary."

The jewel was mined in the Indian city of Golconda.