Experts say the $100 million jewels stolen from the Louvre may already be lost forever. Investigators fear the thieves will melt down or break apart the historic royal gems — including crowns, necklaces, and brooches — to sell the pieces discreetly on the open market. “It could be sold down the street from the Louvre,” said art crime expert Erin Thompson, noting that cutting or recasting the gems would erase their traceability and historic value.