Use any pick axe to remove a total of 10,000 blocks from ANY world. This includes anything that can be removed via pick axe, such as dirt, mud, stone, sand, ore, etc. This is cumulative for your profile and counts across multiple worlds, whether your own or a friend's.
Better pick axes have
faster pick axe speed and remove blocks faster. You start out with a Copper one, but can craft better/faster ones from ore that you smelt into bars at a furnace to use to craft better pick axes at an anvil. Removing blocks with explosives (bombs and dynamite, rockets, etc.) does not count.
NOTE: You will naturally get this through regular gameplay as you need to dig out areas to gather materials for building/crafting.
FASTEST SOLUTION (if boosting)
*** Spoiler - click to reveal ***Create a new world and get a picksaw (dropped from the Golem boss or obtained via duplicating)
Method One
Dig straight down to the Underworld from your spawn point. This should make a giant tunnel 3 blocks across.
Use a Magic Mirror to return to the surface and repeat digging down to the Underworld. It's fastest if you place a bed up there and dig down next to it so the mirror returns you to the bed.
ruudba said:Method Two
Dig towards the bottom of a desert or the ocean from the side (horizontally) until you hit the lowest point.
Dig into the sand. It will continue to fall and allow you to keep "mining" it.
***Same as 360 version***