Six years ago, a Massachusetts police officer was enjoying a bowl of seafood stew at a local restaurant when he spit out a lavender, egg-shaped thing that he first thought was a rock, but later realized was actually a pearl. A rare, six-carat pearl from a quahog clam, to be exact.

According to ABC News, Mike Serino and his wife kept the pearl in a jewelry box until recently, when they saw a news report on a Virginia woman who had made a similar find. Realizing that they might have a treasure on their hands, they began calling auction houses in the area to get an appraisal.

On March 15, the pearl will headline Kaminski Auctions‘ Spring Estate Sale, where it is estimated between $10,000–$15,000.

While the story of a bowl of stew that came to be worth five figures sounds too good to be true, most quahog pearls are found by accident during the preparing or consumption of the clams. However, the occurrence of a gem-quality quahog pearl is estimated to be just one in two million. That’s a whole lot of stew.

“Quahogs go through a mechanical process [that] separates the meat and the shell and, in that process, the pearls normally get ground up and no one knows they ever existed,” said Harry Morgan, Kaminski’s Director of Appraisal Services. “I had never seen one before so when he called me and said he was bringing it in I had no expectations.”

“The first thing I noticed was the color,” he recalled. “I was just overwhelmed by the glassiness and the color and the shape.”

Kaminski Auctions Spring Estate Sale will take place on March 15 at 10 AM. Bids can be made in person, over the phone, and online, beginning on February 28.