A block of iron is a decorative block made from iron ingots.
Blocks of iron can only be mined using a stone pickaxe or better. If an iron block is mined without the use of a pickaxe, it drops nothing.
Blocks of iron can be used to store iron ingots in a compact fashion.
Blocks of iron can be used to "power" a beacon. The layers do not have to be entirely iron blocks; they may also contain emerald blocks, blocks of goldgold blocks, and diamond blocks; however, it is recommended that you use blocks of iron for the beacon, because it is the easiest to obtain.