The couple in Northern California found more than 1,400 coins, dating from 1847 to 1894, stored in decaying metal cans buried in the shadow of the tree on their property in Gold Country.
The coins are in uncirculated, mint condition and the estimated value of the treasure is believed to be in excess of USD 10 million.
This may be the most valuable hoard of gold coins unearthed in North America, according to veteran numismatist Don Kagin, 'CBS San Francisco' reported.
Kagin, president of numismatic firm Kagin's Inc of Tiburon, said the couple wants to remain anonymous and plans to sell most of the coins.
"We all dream about discovering buried treasure; seeing the real thing in person - piles of gold coins encrusted in dirt and rust - the experience was just indescribable," said Kagin Inc senior numismatist David McCarthy who evaluated the coins.
"Never in my wildest dreams would I imagine coins coming out of the ground in the kind of condition that I saw in front of me. Many pieces were finer than anything known in major collections or museums," said McCarthy.
