Is this a live rock?


Reefing newb
Im very new, i have just bought a tank (100L) and filled with water and salt, the bottom of the tank has crushed up corals and sand as the base, have the filteration system running. I bought a rock from the pet shop how do i know this is a live rock? it was not in water or anything.

It has been running for a week now, what else do i have to add or do?

Thankyou, sorry for stupid questions!