This kind of lowers the efficiency of TANS's suggestion, but while mining with this eff5 fort3 unb3 dpick, have another Eff5 unb3 pick so you don't waste all of your fortune pick mining stone. Also, I mine at level 9, and press shift while moving forward, so lava doesn't kill me. If lava DOES start pouring, back up a bit and mine a block from the path to stop the lava from moving toward you.