The St. Augustine Record reports that the man was digging a grave for his dog when he found a rusty cannonball with two ports sticking out of it.
The unnamed man told a St. Johns County Sheriff’s Office officer who called in a bomb squad. They studied the artifact and identified it as a Civil War-era piece.
St. Augustine Lighthouse archaeological conservator Andrew Thompson says there was not a lot of Civil War action in the area.
An historian said the relic could have been brought to the area by a collector, and discarded.
The sheriff’s office says after tests, the mortar will be offered back to the man who found it, or a museum.