Hexagonal Plate Crystal With Dendritic Extensions

December 25, 2018

SnowCrystal_Bentley_0309

December 2018 Viewer's Choice

Photographer: Wilson Bentley (Schwerdtfeger Library)
Summary Author: Jim Foster

The lovely snow crystal shown above is classified as a hexagonal plate with dendritic extensions (P2g), according to the Lee/Magono system. It's part of the snow crystal collection of Wilson Bentley (Snowflake Bentley) that can be found in the Schwerdtfeger Library. The six-sided shape we see in snow crystals is a result of the six-fold symmetry of the ice crystal lattice -- each hexagonal crystal looks very similar when rotated by 1/6 (60 degrees or 1/6 of a circle).

It turns out that even though crystals may have multiple shapes under different temperature and pressure regimes, for the range of temperatures and pressure found on the Earth's surface, hexagonal shapes are dominant. Larger, faster-growing snow crystals generally form when abundant water vapor is present -- growth occurs as water molecules are deposited on crystal surfaces. Such crystals become more branched than smaller, slower-growing crystals.

Wishing you Happy Holidays, Merry Christmas and Peace in the New Year,
Erin Senoz, Stu Witmer, Jim Foster