Dug up in Brazil in 2001 and tipping the scales at 381 kilograms, the boulder-sized Bahia Emerald is one of the largest gems ever discovered.
Several people have laid claim to the hulking rock throughout the years. Today, a small army of lawyers is set to cram into a tiny downtown courtroom, where Superior Court Judge John A Kronstadt will review the case of the man who says he bought it first.
Tony Thomas has said he purchased the emerald from a Brazilian gem dealer for $60,000 shortly after it was excavated. Its worth has since been appraised at almost $400 million.
But after he arranged to have it shipped home, Thomas says he was tricked into believing the emerald was stolen so it could be sold to someone else for more money.
He says it vanished after he turned it over to people who were supposed to ship it to him and, now that it's been found, it should be returned to him.
The case will be weighed from the bench by Kronstadt without a jury, and he will listen to oral arguments about Thomas' claim.
Lawyers for other interested parties have argued the claim should be dismissed because the emerald was never delivered to Thomas, but his lawyer says Thomas did take possession of the emerald in Brazil before it disappeared.