Following the cancellation of a $1.2 billion agreement to purchase Appian’s Brazilian nickel and copper mines, investment firm, Appian Capital Advisory, has filed a $522 million compensation claim against South African miner Sibanye Stillwater, the company announced on Monday.

Last week, the London High Court mandated that Sibanye pay Appian for the lost deal, with a hearing scheduled for November 2025 to decide the exact amount of damages.

“Appian currently claims damages of up to $522 million,” Sibanye spokesperson James Wellsted told Reuters. “Sibanye’s case is therefore that Appian is entitled to either no or significantly reduced damages.”

An Appian representative declined to provide a statement.

In what would turn out to be its largest venture into the battery mineral business, Sibanye announced in October 2021 that it would be purchasing the mines owned by affiliates of funds advising them.

It backed out of the deal three months later, claiming that the Santa Rita mine’s instability would have had a significant negative influence on operations going forward.

According to Wellsted, the claims Sibanye obtained include pre-judgment interest, expenditures and expenses related to the mines’ administration and resale procedure, and the difference between the agreed-upon purchase price and the market value of the shares in the mines.

The financial obligations place additional strain on Sibanye CEO Neal Froneman, who is already dealing with growing losses brought on by a decline in the price of platinum group metals.

According to Wellsted, Sibanye intends to contend that Appian violated a fundamental tenet of English contract law, which requires a claimant to take reasonable measures to lessen its losses.

“Appian is required to mitigate its loss by accepting offers for the mines at fair market value and to account for any profits it has made from its continuing ownership of the mines,” he added.