What's on the volcanic beaches of the Canary Islands then?
I got some lovely black sand from my LFS. Unlike Pettex Roman Gravel sand (which is purply) this is nice and black. It's not a brandname though and they bag it up themselves. I'll ask next time I'm in to see what it's called.
No,it's just like sand,but black.Though I suppose all sand is different grain,but it doesn't look like crushed glass,just sand.
If you're going planted,there are a few good black plant substrates now.