Minecraft wiki entry for Breaking, associated text: When breaking a block, a tool and its enchantments do its speed value as "damage" to a block every game tick, and when that value equals or exceeds the block's hardness, the block breaks. If the tool and enchantments immediately equal or exceeds the hardness times 30, the block breaks with no delay; otherwise a 6 tick (3⁄10 second) delay occurs before the next block begins to break.