The lava bush makes it possible for you to grow and harvest lava!
Works exactly like any other bush. You plant it, watch it grow and then harvest the berries! When you harvest the bush you get Lava Berries.
To make a bucket of lava, simply put the berries around an empty bucket in a crafting table.
You can also use Thermal expansion and Forestry machines to get lava out of the berries!