Gold mining! A six-pound gold nugget, discovered with a metal detector in Northern California’s Gold Rush Country, is valued at $400,000.

A palm-sized, 6.07-pound Gold Nugget found at a depth of just 12 inches by a metal detector enthusiast in Northern California’s fabled Gold Rush Country was sold last week to an anonymous buyer for $400,000.

The massive nugget, which was originally thought to be an “old pipe” or a “big piece of trash” because of the unusually high reading and loud sound it generated on the metal detector, was unearthed in July in the foothills of Butte County on public land. The nugget has been dubbed the “Butte Nugget” and the lucky prospector has chosen to remain anonymous.

Interestingly, the well-worn nugget (front and back views seen above and below) was discovered in an area that was worked in the mid-1800s during the original Gold Rush. In fact, the largest gold nugget ever to emerge during the 19th century Gold Rush days was reportedly a 54-pound chunk unearthed in Butte County, Calif., in 1859.

Kagin’s Inc., a numismatic firm based in Tiburon, Calif., was given the exclusive rights to market and sell the Butte Nugget. Only one day after revealing the specimen to the wide-eyed attendees of the San Francisco Fall Antiques Show last Thursday, Kagin’s announced that the nugget had been sold to a “prominent San Francisco Bay Area collector” for approximately $400,000.

Kagin’s had estimated the sale price would be between $350,000 and $450,000. The precious metal value of the nugget is $119,554 at today’s spot gold price.

“Nuggets like this don’t come along every day,” said Kagin’s senior numismatist, David McCarthy. “I really didn’t believe that I would see a California nugget of this size unearthed during my lifetime.”

Despite its enormous size and weight, the Butte Nugget is believed to be the second-largest California nugget in existence today. In fact, it’s only about half the size of the Mojave Nugget, which was found near Randsburg, Calif., by prospector Ty Paulsen in 1977. That nugget, too, was located using a metal detector. The 156-ounce Mojave Nugget was ubsequently donated to the Natural History Museum of Los Angeles County.

The largest gold nugget ever discovered was named “Welcome Stranger” and weighed an astounding 158.78 pounds. It was found at a depth of only one inch by Aussie prospectors in Victoria in 1869.

At 24 inches wide, the nugget was so large and so heavy that the gold scales available at the time couldn’t handle it. The miners decided to smash it into three pieces so the weight could be taken. Eventually, the world-record specimen was melted down into ingots and shipped to England.