Minecraft wiki entry for Slime_farming, associated text: Both slime blocks and sticky pistons, which are crafted using slimeballs, are essential in many redstone builds. Slimeballs can also be crafted into magma cream, which is needed for brewing potions of fire resistance. Because slime blocks break instantly when hit (with a bare hand or any tool), they are useful for quickly displacing and clearing out volumes of water, even when under the effect of Mining Fatigue inflicted by an elder guardian.