There is a mine cart to the left before the entrance to level 1 in the mine. The cart will take you down to level 20 in a click if you have visited that level before.
(Just learned this a few days ago myself)
Oh, fantastic! That makes a huge difference, thanks!
Whoa. I feel like that cart thing needs to be explained somewhere—like a sign or cutscene or something. Mining is rough... that info would help a lot.
I agree with you there. :) I had forced myself down to lvl 80 many times to mine ore before i found out.