Maybe I am missing something. OP asked for "black aragonite sand". I don't think there can be such a thing. Calcium ain't black.
I am not sure where the bagged stuff comes from, but in nature the black sand is usually volcanic. I have a few bags for a future FOWLR, and IMHO it appears more sharp and crystalline then aragonite. I would not use it for burrowing animals, or in a reef, as it has no buffering qualities.
Dry fine aragonite can be had at my local Petsmart (maybe Petco, can't recall) for $1.00 lb in 20 lb bags.