Blackhawk Mining LLC is offering to buy bankrupt Patriot Coal Corp.
Patriot says it's teaming with Lexington, Kentucky-based Blackhawk on a $643 million bid.
The "stalking horse" bid would set the floor for an auction process that lets competitors make better offers. The deadline to submit competing offers is Aug. 7.
Patriot, based in Scott Depot, West Virginia, said Wednesday it outlined the proposal in U.S. Bankruptcy Court for the Eastern District of Virginia.
Patriot has eight active mining complexes in West Virginia. The proposal doesn't involve Patriot's Federal No. 2 mine in northern West Virginia. That would involve a separate "stalking horse" transaction from a yet-undetermined bidder.
Patriot Coal filed for Chapter 11 bankruptcy protection on May 12.
Blackhawk has five mining complexes in Indiana, Kentucky, and West Virginia.