A few issues with black sand that should be considered. First, it is black and absorbs much more light and transfers that as heating the water. It also absorbs light rather than reflecting it back to the corals. It has no buffering capacity as it is ground lava, not coral. But the worst thing is that it can contain metals that are very bad for the aquarium. Not all of it does, but some, and it isn't simple to test for it. So if you got it from a reputable aquarium supplier, it is all glass with no soluble minerals in it and would be safe to use.
It sure is pretty, I agree. Just remember the potential down side to using it. I collected some of it off a beach in Hawaii once, but didn't use it for the reasons I just gave, plus I was told that by removing it from Hawaii, I was cursed. I eventually returned it on another trip.