I don't have marine fish, so never delved into marine sand that aragonite or whatnot. Here's a cool link to the color and sizes of 3M Color Quartz, there's also Estes on that page and whatnot. I saw someone's tanks with white/yellowish and black sandblasting sand and from what I could tell it looked like a reef almost, although there were Cichlids in there. Here's also an article with pictures on different types of sand.
You will get conflicting advice on the iron slag, Black Beauty type sand though, some saying there are sharp pieces in there, and others who actually have the stuff in their tank say the Cichlids rummage through there just fine, and that they are also smart and know how to sift sand so it doesn't hurt them, even if there were sharp pieces, it's no more different than crushed coral they say. I bought a pack of Tahitian Moon, and I love it, but I don't love the price, and so next time I'm going to get different cheaper sand that gives the same black effect. It's black too, not greyish black.