An enormous emerald valued at upward of $400 million is at the center of a legal battle to determine ownership of the gem that was unearthed almost a decade ago in the jungles in eastern Brazil.

Anthony Thomas, who claims to be the 840-pound gem's first buyer, tried to convince Superior Court Judge John A. Kronstadt Friday that none of the half-dozen or so other claimants has a right to the so-called Bahia Emerald.

The soft-spoken businessman took the stand for several hours to stake his claim that he bought the boulder-sized gem in 2001 for just $60,000 soon after it was pulled from a mine in the jungles of Brazil's Bahia state.

He said he wired money to the emerald's Brazilian owners, but it never arrived. Instead, he said he was tricked into believing it had been stolen so it could be sold to someone else for more money.

"In my mind, I was the owner when I agreed to pay them," Thomas, 47, told the court.

The emerald is a hulking brute of a gem, with several thick green rods the size of a man's forearms jutting out of a stone base.

"It's pretty impressive," said Kit Morrison, another claimant who had possession of it in 2008.

A Brazilian appraiser has previously put the gem's worth at $372 million.

Lawyers say the well-traveled stone has made stops during the past nine years in California, Las Vegas and New Orleans, where it was kept in a bank vault that flooded during Hurricane Katrina, leaving it underwater for months.

Steven Haney, a lawyer for another claimant, Mark Downie, said Thomas had never taken actual possession of the gem and failed to contact Brazilian authorities after he thought it was stolen.

"His story is inherently unbelievable," Haney said.

Thomas' attorney, Jeffrey Baruh, said his client is a man of great integrity who alerted the Santa Clara district attorney's office to the emerald's disappearance, only to be told the matter fell outside of local jurisdiction.

Thomas said he traveled twice to Brazil in fall 2001 to look at the emerald and arrange to have it shipped to his home in Morgan Hill, near San Jose. He was photographed squatting down next to the jumbo rock, an arm draped around it and a big smile on his face.

Lawyers for other claimants argue that though Thomas went to Brazil, he never took possession of the emerald and so is not the owner.

Asked why he didn't shipped the gem back to the U.S., Thomas said he had to return home for a family emergency and did not have time to build a crate.

Adding to his woes: a bill of sale he claimed to have for the emerald was destroyed in a 2006 fire at his home.

Attorney Andrew Spielberger said the $60,000 that Thomas sent was actually to pay for other gems and polishing services previously carried out by the emerald's owners.

The emerald came into the U.S. in early 2005 and was kept in San Jose before being taken to New Orleans, according to Spielberger, who represents another group of claimants.

Morrison, who is part of that group, says they have legal ownership after receiving the emerald from a gem dealer as collateral for a shipment of diamonds he paid $1.3 million for but never received.

Morrison was trying to sell the gem in Las Vegas when authorities confiscated it. The Los Angeles Sheriff's Department now has it under lock and key.

The trial will resume at an unspecified date, with Thomas set to conclude his testimony then. Other claimants will address the judge later.