Updated: Dec 21, 2022
The fastest mining training method in the game is 3-tick 4 granite. This is done at the quarry in the desert and with tick manipulation, you can get 130k xp per hour at 99.
You unlock granite at level 45, and even at 45 it’s the fastest method in the game, giving up to 70k per hour. Granite is only good with tick manipulation though, so 3-ticking each rock you mine, because without it your xp rate caps out at around 60k per hour at 99.