As if it weren't enough that lightning has been known to strike twice in the same place, scientists have found two lookalike snowflakes.

The matching snow crystals were discovered during cloud research by Nancy C. Knight of the National Center for Atmospheric Research in Boulder, Colo."One of the most quoted statements about snow crystals is that no two are alike, a bit of folk wisdom that is generally accepted even among those few regarded as experts in the subject," Knight wrote in a letter just published in the May edition of the Bulletin of the American Meteorological Society. But, she went on, she has found "a striking example of two snow crystals which, if not identical, are certainly very much alike."

"In many years of snow-crystal collection the author has seen no other examples of such crystals nor are any given in the standard references," she wrote.

But there the two crystals were, side by side, on a slide exposed in a cloud on a flight over Wausau, Wis.

The crystals photographed by Knight are shaped like columns with vase-shaped hollow centers. They are very tiny, only one-quarter millimeter (0.009 inch).