SALT LAKE CITY (AP) — A man searching for unique rocks in the Utah desert near the Nevada state line recently made an explosive discovery: a World War II-era bomb.

Craig Alvord told Salt Lake City news station KSL-TV this week that the 6-foot-long bomb is the best find he's made in more than 50 years of searching for stones.

Alvord notified the Air Force about the bomb. Though it wasn't discovered within base boundaries, Hill Air Force Base spokesman Richard Essary says its bomb squad detonated it Tuesday afternoon with C4 plastic explosives.

Essary said it appears to be a practice bomb from the World War II era. It may have ended up there because of a test range in the area.