Black hole's aren't matter, they're pure gravitational binding energy. A neutron star becomes a black hole when the neutrons pushing against each other can't push back at the gravitational forces (neutron degeneracy pressure) and the neutrons do something we're not sure of... but whatever happens, they're crushed down into something smaller than a neutron star; into a singuality and we see the result.. a black hole. Eternal darkness for the poor neutrons; this bit gives me chills.
Black holes are not made of matter… the matter has collapsed into pure energy. The form of energy is a mystery (it’s inside the event horizon) but since the gravitational field persists, it’s often referred to as pure gravitational binding energy. I graduated physics at Manchester Uni and I’ve still got a ‘preference’ to be as correct as possible when talking about BH’s and what they’re ‘made’ of. Kip Thorne also often refers to the stuff BHs are made of as ‘gravitational binding energy’ so I thinks it’s safe to do the same.
In GR, black holes have only three distinguishable properties: mass, charge, and angular momentum. If you have one made from matter, one from antimatter, and one from sufficiently concentrated light, all three are indistinguishable.
As I'm not a physicist, I wouldn't risk phrasing this as "pure gravitational binding energy" just in case this has a specific and different meaning.
I read the interior of an event horizon immediately causes problems with quantum mechanics' no-cloning rule, so I suspect the actual problem here is "QM and GR are fighting again" and we can't get any answer until we've resolved that.
