If you bought the chick, where?
If you hatched it, what do you know about the parents?
It looks like a Black [something].
Could be a pure breed, such as Black Australorp.
Could be a hybrid, such as a Black Sexlink.
Someone who has a mix of hen and rooster breeds might well end up with some black chicks, too. (Several common breeds tend to produce black chicks when crossed with other breeds.)