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Unusual Snow Crystals |
In addition to the normal snowflake forms (see Guide to Snowflakes), there are also many unusual shapes that can be found floating from the sky. Some of these are described here, with photos from the Rasmussen&Libbrecht collection (see Photo Collections). And, of course, you can find even more in our new book.... |
Not Your Ordinary Snow ... |
12-Sided Snowflakes |
Triangular Snowflakes |
Bullets Bullets form when several columnar crystals grow from a single nucleus, a beginning that is similar to the spatial dendrites (see Guide to Snowflakes). Bullets always start out in clusters, but the clusters can break up to yield individual bullet crystals. |
Arrowhead Crystals Crystal twinning is a phenomenon whereby two crystals grow out of a single seed and have a specific crystallographic orientation relative to one another. One example is found in arrowhead crystals, which occur along with columns. The unusual shape results from the way the two crystal halves are joined. The seam between the crystals can be seen when some of the ice evaporates, leaving an evaporation groove, as indicated in the picture at right. |
Twin Prisms Another example of crystal twinning occurs when twin columns grow from a common center, one rotated 60 degrees relative to the other. The growth looks like an ordinary column, but again we can find an evaporation groove that indicates twinning. Twelve-sided snowflakes also form by columnar twinning; in this case the two columns are rotated 30 degrees and the assembly grows into a capped column (see Guide to Snowflakes). |
Pyramidal Crystals |
[1] W. Tape, Atmospheric Halos, Antarctic Research Series, Vol. 64, (American Geophysical Union, 1994). |