Looking to Buy black sand

As long as it's just quartz sand, should be fine. Sandblasting sand is what it is sometimes called. I did a bit of research into types/brands a while back but don't recall what I concluded, it was for a FW tank.

Whatever you read, just remember that just because it says it is silica sand or has silicates in it does not mean you will grow algae from the silica. Sand=silica=glass there is no problem, it's locked up as a solid.
google search "black sand reef safe" some good threads. Summary: doesn't have any buffering capacity, and if you pass a strong magnet over it and it reacts, don't use it.

 

Look at the MSDS, lots of metal. I would dig a little deeper to make sure that's reef safe. Although I think that's the stuff I looked at using