Minecraft wiki entry for Block_and_item_duplication, associated text: Start by obtaining at least 2 dirt and gravel from bartering. Next, craft coarse dirt using 2 dirt and 2 gravel for 4 coarse dirt, then till the dirt and mine it to obtain 2 extra dirt. With a bartering farm, a good hoe, and a good shovel, you can mass produce dirt in a matter of minutes. However, this is not perfect duplication, as you will need a constant supply of gravel.