Minecraft wiki entry for Cobblestone_farming, associated text: Pistonless generators have been around for quite a while. However, Their usefulness is limited because cobblestone is so readily available. These generators require the player to mine and collect the fresh cobblestone in close proximity with lava. This both presents risks to the player and reduces efficiency if the dropped cobblestone is destroyed by the lava. These drawbacks can be mitigated by design choices, for example by removing the block under the cobblestone, allowing the loot to fall in a safe place, or collecting drops using a hopper.