I think Mark is right! 

I wanted something a little different when I was setting up my 125.  I didnt want to buy a ton of Indo-Pacific Live sand which is a mixture of black and white sand.  Looking at Carb-Seas on-line catalog, they had some stuff listed called Tahitian Moon.  Its wasnt queit the same as the black in Indo-Pacific.  It was sugar grain in size and I rather suspect as Mark said Osidian, at least it looks that way.  It reminds me very much of the black sand beaches of Barbados!  The Indo-Pacific though is made with what appears to be black volcanic sand.

At anyrate I got 40lbs of it, 20lbs Fiji Pink, 40lbs Special Reef Grade, and 60lbs of Indo-Pacific Live sand.  It came out pretty good when mixed together.  I think it looks awesome!  It has a nice salt and pepper look to it.  I am the only person that I know of running this type of mixture in my area.  It does indeed make for a very strikingly look!

It's not necessarily only ornamental.  It really depends what kind it is.  Caribsea has a sand called Indo-Pacific Black (1-2 mm, Aragalive Water packed bag) that is "the same pacific rim ecosystem reef sand as found in Hawaii, Bali, Sumatra, Costa Rica, Tahiti and Java. This sand has a striking combination of jet black volcanic sands and pure aragonite."  This info is from CustomAquatic.com (http://www.customaquatic.com/customaquatic/listcat1.asp?CatID=ss). 

I'm in the process of setting up a new mini reef tank (~17 gallons), so I've been doing a lot of research on different sands.  I ended up falling in love with pink sand and ordered a couple of different kinds (Caribsea Bermuda Pink and Arag-Alive Fiji Pink) from the web site above.  Maybe next year I'll get a chance to show it off in the Reef Tour? 

I was under the impression that it was an obsidian which is quartz.

A school of neon and/or cardinal tetras looks awesome over black gravel and dark background! Live green plants made that tank a wonder to behold!

If coupled with an RDP refugia using CaribSea aragonite that black sand would make a neat main tank. But I wouldn't do it alone with more than a few fish.

My two cents worth.

What kind of sand is it?  I'm guessing it's not quartz?

Here's my thought on this.  Doesn't have the benefits of other substrates.  However, it is the coolest best lookin' stuff you can get.  I've only seen a few tank set up with it, but boy do they stand out as awesome tanks. 

Adam

I only ask because I've never seen or heard anything about till I stopped by Bird World the other day and saw Black sand, I'm pretty sure it's only ornimental, but am I correct?  Is there any benifit/or lack there of?

PS I got my fish books, The Concientious Aquarist(however you spell it) and the New marine aquarium!  I'm so excited, thanx for teh ideas on books everyone!.

David