Blue Ice
Alaska
Glacial ice crystals can enlarge to the size of a basketball. These ice crystals can transmit light, though that light is curiously modified in its passage. Long-wavelength reds and yellows are absorbed by ice, while blue wavelengths wriggle through the lattice structure just fine. Thus, though full-spectrum sunlight enters a glacier, only blue light emerges. Photo © copyright by Robert Faucher.