I think most sand, like child's play sand and pool filter sand as well as some sand blasting sand, the light colored one has silica also, it is even in beach sand, it is what they make glass with.
I can't say about the black diamond type sand, someone said it was a byproduct from coal, I thought it was actually sand, personally haven't had a chance to get any additional info...I would just check on what it is. Coal by product dust probably isn't good for you either, just wear the little hospital mask or shop mask and wash yourself and clothes to get the dust off. Even the crystal and pearl cat litter is made from it (silica gel). It is from natural sources.
oh ok. well thanks for the heads up! ill be cautious