Copper blocks can be used in construction. They are also conductive and can be used to transfer electricity through blocks.
Hardness
Blocks crafted at the metalwork bench have different hardness depending on which ingots were used. A flint pickaxe takes about 16 Seconds to mine one copper block, a stone pickaxe takes ~8 Seconds, bronze takes ~6 Seconds, Iron takes ~4 Seconds and steel takes ~3 Seconds.