Wednesday, August 08, 2012

Reflective street crystals

One of my favorite pieces of natural urban beauty are these "street rainbows" I see once in a while.

It's caused by a sandy powder on the roads.  I'm fairly sure it's a kind of retro-reflective crystal used to make white road lines shine brightly in car headlights, because as you can tell from my shadow in the photo, the effect only appears when the sun is almost directly behind my head.

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