The unknown metal block is what makes up the majority of the UFO structure. This can be mined to obtain.
Unknown metal blocks require at least a stone pickaxe to break
Found in the "Building Blocks" creative tab
Hardness: 6
Resistance: 10
Slipperiness: 0.6
Jump Factor: 1
Speed Factor: 1
Each block of unknown metal contains three nuggets worth of iron, which can be extracted by placing it in a crafting table.
It can also be used for decorational purposes and as a "false iron."