I have only just gotten back into the game after a year or so off. What are mining claims?
There are now two dilithium mines in Beta Ursae sector.
There's a fleet owned dilithium mine where fleet members can mine 8? dilithium nodes. The amount of dil mined varies between 1000 to 3000 depending on the tier of the dilithium mine.
Then there's the public mine where captains can mine 3 dilithium nodes each day, giving you around 1000-15000 dilithium. Opening lockboxes will sometimes give you VIP mining claims that allow you to mine a rich dilithium node that can net you around 4000 dilithium.