Off Topic » in reply to Would the resident geologists weigh in on this one?
http://farm1.static.flickr.com/44/159780219_409fadf7a5.jpghttp://farm1.static.flickr.com/69/159780793_3d416709a9.jpghttp://allhatnocattle.net/rainbow-cloud-06.jpgsome explanations here... Google image for cloud ice rainbow you get several hundred hits...