Mysterious Ice Colours
In December 2008 mysterious colour fringes could be observed on a frozen water basin. They occured mostly along thawing fringes, but were quite prominent on the thickest parts, where the ice had molten and refrozen. Some close-ups suggest a film or even a layered structure. Enclosed air, homogenous organic or rust particles, air entering ice fissures or even birefringence - these colours are not easy to explain. A polarizing filter did not change the look of the ice surface.
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