(Reuters) - A 5-pound gold nugget dug up in Northern California this past summer and believed to be the largest privately held piece of its kind from the state was offered for sale at $400,000 on Thursday.
The chunk of gold, which is the size of a misshapen baked potato and weighs 72 troy ounces, or about 5 pounds (2.3 kg), is on display at the San Francisco Fall Antiques Show from Thursday through Sunday, said David McCarthy, senior numismatist for Kagin's Inc.
The California-based numismatic firm was billing it as the "Butte Nugget" because it was unearthed in Butte County in Northern California by a man prospecting for gold on public land in July, according to the company.
The firm did not identify the man for whom it is selling the nugget or where in the county it was discovered.
"There are bigger ones in museums and there were bigger ones certainly near the Gold Rush period, but today it's believed to be the largest gold nugget in private hands in California," said Donald Kagin, president of Kagin's.
McCarthy, who evaluated the find, said the man who found it photographed its excavation step by step and took McCarthy to the spot where it was unearthed, but not before blindfolding him.
"I've seen the pictures of the nugget being slowly exposed as he was digging it up, it was very obvious it had been in the ground for a very long time,” McCarthy said.
Kagin's earlier this year offered for sale pieces from a trove of rare Gold Rush-era coins that were discovered in California last year by a couple walking their dog and assessed at more than $10 million. Many of the coins were offered on Amazon.com.
Adrian Ash, head of research at gold and silver exchange company BullionVault, said in an email the gold content was largely irrelevant and that the nugget's value derived from its unusual size.
"Unlike a big diamond, its price would be destroyed by working it into an objet d'art," Ash said.
McCarthy said that if someone agreed to pay the $400,000 asking price for the nugget before Sunday, he would seek to have it remain on display until then.
Reporting by Alex Dobuzinskis in Los Angeles; Editing by Dan Whitcomb, Lisa Shumaker and Peter Cooney