Check out this thread http://www.aquariacentral.com/forums/showthread.php?t=56245 I asked the question about sand and it got a few more hits.
Kasakato said:To test the rocks drop some vinegar on them. If it fizzes they are no good. If there isany rust on them also toss them. Another test you can do will make sure of it 100%. Take a bucket of tap water and use de chlor. Test the pH of that, and add the rock. Wait 24 hours and test again, If it changed a lot its also no good.
I cant tell what kind of sand that it. Is it play sand? Pool sand?