okay, this might be a very silly question but whatever. If a black hole were composed of antimatter, would we be able to tell? If the black hole were created by anti-matter collapsing and becoming dense enough to turn it into a black hole, then if regular matter fell into it, it wouldn't annihilate, correct? Or rather, would we be able to tell, as a distance outside observer, if the black hole was annihilated? What I'm assuming is basically that the anti-matter black hole is there from the beginning, and then a black hole of similar mass in regular matter were to collide with it. I know that if two black holes of regular matter collide, then they become a single black hole with the mass of the two original ones added together. But if they were two black holes of regular and anti-matter, then wouldn't the matter at the center be annihilated? But wouldn't we never be able to find out? The black hole would remain a black hole, yes? Would the black hole's mass increase, even though it should annihilate? I am pretty sure that we would be able to notice if the mass of the black hole increased or went away if it were annihilated.