I see a lot of folks referring to "dead" rock, and keep saying that it will eventually turn into live rock.
This may just be a question of semantics - but LIVE ROCK in the marine hobby is actual pieces of a natural coral reef in the ocean, pieces that have been collected, cured, shipped and eventually placed into our tanks. It was once ALIVE meaning it was a living coral - and we utilize these once alive coral skeletons in our tanks. It is not really a rock as we know it.
Other rock that we place in our tanks, such as tufu, lace or this coral rock ?? is what I consider rock. It was never alive in the sense of being a living creature, it has very little porosity, no calcium skeleton, it's just a freaking piece of rock.
I suppose you can call it "DEAD" rock if you want to. Personally I prefer the term "BASE" rock.
As Mr. Salty and others have mentioned, this base rock will provide a place for bacterial to grow and small marine critters will live on it. It makes excellent rock to lay down as a first layer when stacking LIVE ROCK.
If your water parameters are in check, alkalinity and calcium level maintained, and you have some true live rock in the tank, live rock that has some coralline algae growth ... then purple, pink and red coralline algae may begin to grow on it, and it will take on the appearance of true LIVE rock over time.
But this by no means that this base rock is now considered LIVE ROCK.
It's very porous