Diamond is the hardest material in Angry Birds that the Pigs use for their structures. It is extremely difficult to break for almost all birds, except for Rotten Bird's Rotten eggs. 5 Big Brother Bird or 5 Black Bird's explosion can break it. The Purple Bird can make it weak. Even though the Purple Bird makes it weaker, it's still very difficult for Birds to break. You need 3 Drill Birds to break it.