I've just discovered the amazing twitter feed Chemical Reactions, which goes by the appropriate handle of @holdmybeaker. It shows astonishing chemical reactions, many of which are much faster than this geode-like crystalline structure made with copper sulfate. Some of them are classroom demonstrations that may have been a bit more dangerous than the teachers planned.
-via Super Punch
Comments (2)
The effect likely comes not from diffraction as seen on a CD, but from thin film wave interference. The Naked Scientist (link below) has the best, quick description that I could find. Google "Oil Rainbow Effect" to get more information.
http://www.thenakedscientists.com/HTML/questions/question/1708/