Van,

First off your sand is live. If it is an established tank it has developed the microbial community that make us consider it alive. I would keep the rock if you plan on another tank. If you use it in a start up tank and will let it cycle then you can just though it back in tank. It will start the tank cycle with the dead organic material on it and as long as it is new tank and no inhabitants then it will do fine. It will surely become live again with proper care, however it would be nice to find a piece of rubble with some coralline on it from a friends tank to help out the process when you start.

Mike