A diver discovered a 40.2-carat emerald embedded in a conch shell while diving at the site of a Spanish galleon wrecked in a Florida Keys hurricane 380 years ago.

The diver, who unsurprisingly does not want his name revealed, discovered the giant raw emerald while washing shells in a classroom laboratory. “Out popped a 40.2-carat emerald,” Patrick Clyne, vice president at Key West-based wreck salvage company Mel Fisher Enterprises, said Monday. “It was one of those freak-of-nature things that somehow got swept up in the conch shell.”

The diver had gathered the shells from a dive off the Spanish galleon Santa Margarita, which sank Sept. 6,

1622, about 30 miles west of Key West. “This is an excellent indication that the Margarita had raw emeralds

smuggled aboard the ship,” Clyne said. “There were no emeralds listed on its cargo manifest.” There were no

estimates for how much the emerald might be worth. But in 1985, a 77.7-carat emerald from the vessel

Nuestra Senora de Atocha, a sister ship of the Santa Margarita, was appraised at $1.2 million. The vessels,

part of a 28-ship fleet that left Havana on Sept. 4, 1622, for Spain with treasures from Colombia, Mexico, Peru and Venezuela, sank during a hurricane.