http://img96.imageshack.us/img96/8491/imag0256j.jpg
Looks like glass and is greenish. Is it natural or man-made?
I’m no expert, but I would say man-made glass.
Obsidian is more opaque, has more inclusions, and is darker.Yours is blueish.
It is not crystal, quartz or even smokey quartz; that would have a more crystal shaped stucture.
Looks like glass to me.
Any additional details on where you found it?
I looks like an aquarium decoration made from glass. It is glass for sure.
Not sure, but try brandishing it in the direction of Superman if you see him.
My sister has a chunk of glass that looks exactly like that. She got it from a guy that worked for the plant that made windows and windshields for Ford trucks.
Too clear to be Trinitite
I have a chunk of it at home that I use to knock out arrowheads
common to find them in rock shops, ‘junk’ stores and pet stores