I'll always give the same answer to this question regardless of how the sand is treated. The beach is the protein skimmer of the ocean, the nasty crap collected on the beaches is not something I would risk in a tank, not to mention potential chemicals in the sand... you just don't know.
Additionally, if this is sand that is up on the beach, always kept dry (i.e. the waves never reach it) then it probably contains a lot of silicate. Also not something I want in my tanks.
