Brookite.
I actually bought this crystal by mistake: I was going through mindat.org looking up the name of every single mineral that contains thorium, then searching on eBay to see if I could buy one of them. (I needed more pictures of thorium crystals to use for the short-lived radioactive elements that appear in the thorium decay chain.) For some reason I got confused and bough this one too: It's titanium dioxide with no hint of anything radioactive. But it's pretty just the same!
This is officially described as Brookite and smoky quartz from Magnet Cove.Source:eBay seller crystaldiggerContributor:Theodore GrayAcquired:20 September, 2005Price: $29Size: 2.2"Composition:TiO2