by no means am i 100% sure on this, but here is a stab at it,
the rock itself is dead , it will regain life form but not on it's own, you will need to mix it in with a few good pieces of live rock or some sand will also help to seed it
The previous poster is correct. You can use the dead rock in the tank again. In order for it to become live again or for it to grow coralline algae it will need to be seeded with a few good pieces of live rock!
I had a few pieces of "formerly live" rock in my tank which I put in there only because I really liked the size and shape of them. It took about a year or so, but they are beautiful now. I mixed them in with the rest of the live rock. I was worried about them possibly carrying some sort of cooties since they had come from a really "challenged" tank about 6 months previous. If you keep your calcium and other levels premium, then you should not have a problem regrowing corraline algae and other things on them. Some sites sell corraline booster plugs (I think IPSF does) that are supposed to accelerate the process. Be patient.......