BLM and USFS are just land management agencies. They manage our public land through the enforcement of regulations - they don't not own it.
If the mineral estate has not been withdrawn from the public domain, you can generally file a claim on public land.
It gets tricky when public land has been patented out to private ownership, then the mineral estate is excepted out (retained) prior to trading/selling the land back back to the government.
Around here the rail road companies traded off the non-timbered ground to consolidate their holdings.
I would be surprised if there wasn't a bunch of info at that web site explaining the in's and outs of filing a claim.