Asteroid Iron Ore
Uses are equivalent to Iron Ore.
It can be found anywhere between the layers of Y=0 and Y=256 in single block form, or (rarely) as the solid core inside large asteroids.
Note that it requires an Iron Pickaxe to mine it. If you are in Asteroids Challenge game mode and you do not have a pickaxe capable of mining it, then you will have to try to have an Evolved Creeper explode nearby this ore and gather a few blocks of ore that way.