Posted by: David Green | January 11, 2010

Frozen world in miniature

There isn’t much plant or animal life to see at the moment, but the cold weather did produce a beautiful crystalline frosting on the snow surface. Complex hexagonal ice crystals up to about three millimetres long reflected early morning sunlight in the garden on Saturday morning. I set a microscope up in the garage to get some pictures.

Beautiful complex ice crystals, 1.5 mm long, in the garden on saturday morning

The crystals that form a hoar frost on the snow are hexagonal, just like snowflakes. They crystallise directly from the cold air as thin skeletal plates. Crystals that form directly from the vapour phase commonly have a large surface area to volume ratio, and ice is no exception. Another substance that forms in this way is sulphur, which crystallises in complex skeletal aggregates around volcanic fumaroles.

Draperies of sulphur around a volcanic fumarole

But that’s another story.

David Green

Curator of Mineralogy

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