Minecraft wiki entry for Infested_Block, associated text: When mined with a tool enchanted with Silk Touch, however, the equivalent non-infested block is dropped without spawning a silverfish on all game difficulties. Any Silk Touch-enchanted tool (including swords) will cause an infested block to drop its non-infested equivalent (that is, a pickaxe is not required). A player wishing to collect stone bricks from a stronghold safely should use Silk Touch-enchanted pickaxes.