LAKE WORTH, Fla. —  A husband and wife are rubbing their hands with glee after finding a valuable gemstone — in their dinner.

George and Leslie Brock were chomping on a plate of steamed clams when they made the unusual discovery in Lake Worth, Fla.

Halfway through the $10 dish at Dave's Last Resort and Raw Bar, Brock bit down on something hard.

He and his wife were astonished to find a rare, iridescent purple pearl among the shellfish.

And they are hoping to cash in on their good luck after experts suggested the find could be worth thousands.

"Few are round and few are a lovely colour, so this is rare," gemmologist Antoinette Matlins told The Palm Beach Post.

"I think they have found something precious and lovely and valuable."

Purple pearls are most commonly found in large New England quahogs, clams known for violet colouring on the inside of their shells.

The Brocks' plate of clams came from Apalachicola in the Florida Panhandle, said restaurant manager Tom Gerry.

But they won't be turning the pearl into a piece of jewelery or putting it on display.

They plan to have it valued and said they will sell it if it is worth a lot of money.