As strange as it may sound, this is too small of a deal for Buffett and BRK. BRK is so big now that only major deals can move the needle and bottom line for them. And, that has been indicated to be deals of at least $20 Billion+.
That having been said, there may be some strategic benefit here for Buffett and BRK, if they were to perceive that owning this mine would provide strategic benefits and synergies for Precision Castparts, which was their latest major acquisition.