An Up-Close Look at 5 Unique Snowflakes

The winter solstice is almost upon us, and for most of us, that means snow is coming. Snowflakes are beautiful works of art by nature, but sometimes it is hard to see their real beauty. Kenneth Libbrecht has worked tirelessly to document this. He has studied snowflakes and photographs them. In his new book, Field Guide to Snowflakes, he highlights certain snowflakes and the traits they demonstrate. Here are five of these unique snowflakes.

White Snow

The above photograph, shows a snowflake as you might see it on your sleeve (provided you are wearing black). Although you may have thought snowflakes were white, if you look carefully, you will find that many are transparent, like glass. In the above example, you can readily see the black background through the clear ice.  Mostly what you see in the picture are the various edges because these scatter the most light. Snowflakes and snowbanks look white because you see light scattered from all the edges; it’s the same white you see on a surface of scratched or etched glass.

Exceptional Symmetry

Occasionally a snow crystal will exhibit an especially precise sixfold symmetry, as in the specimen shown above. If you look carefully, you can see that even most of the minor markings are reproduced with good fidelity six times around the crystal. I took this photograph early one January morning in Fairbanks, Alaska, when the temperature was a brisk –18º C (0º F) and the crystal facets were sharp. The crystal measures about 2 mm (0.08 inches) from tip to tip. Smaller, simpler, faceted crystals like this one tend to be more symmetrical than larger, complex, branched ones. Slower growth is generally more stable and produces smaller, more symmetrical crystals.

Ridges, Ribs, and Rims

This small hexagonal plate shows all three of these design elements. The plate started out as a faceted hexagonal prism, as most plates do. Ridges formed at the corners when the plate was tiny, and the ridge growth changed with time as the crystal moved about, which resulted in the somewhat flowery pattern near the center. When the crystal was about half its final size, the humidity dropped and the edge of the plate thickened as it grew. After a short while, the humidity increased again and the edge thinned, leaving behind a fairly broad rib in the process. Then the crystal fell into a region of low humidity during the last phases of its growth, producing a thick rim around its outer perimeter. This specimen is just over a millimeter (0.04 inches) in diameter, hardly more than a speck when seen with the naked eye. Even a good magnifier will not reveal these features, so a microscope is needed to make out the details. As you can see, taking a close look has its rewards. One of the great pleasures in finding and photographing snowflakes is that even the most inconsequential crystal is decorated with its own elaborate pattern.

Hollow Facets

For this photograph, I focused my camera on one face of a diamond-dust prism, about 0.3 mm (0.012 inches) in size. I caught this crystal quickly on an especially cold day, so sublimation had not yet taken its toll; the corners are still distinct and sharp. I like this picture because it’s a good example of the hollowing sometimes seen in prism facets. During growth, diffusion gives the corners of the crystal a greater supply of water vapor. The facet centers receive less, so they accumulate material more slowly. With time, the facet centers lag behind the growth of the edges, as shown in the sketch at right. This is a common growth behavior and is the first step in the transition to branching (see page 19). Had this crystal grown larger, it soon would have abandoned its simple prism shape as it developed into a more complex structure.

A Simple Hexagonal Plate

Crystals like this one are easy to find in most snowfalls, provided you use a microscope. All you usually have to do is let some snow fall onto a few glass slides, and then scan around looking for interesting specimens. Many of the snowflakes I’ve photographed were found using this straightforward technique.  The markings you see on this crystal were caused by variations in temperature and humidity it experienced during its travels. Each time its local environment changed, the crystal growth behavior changed. The resulting surface markings are mostly remnants of these variations in growth. Had the crystal formed under perfectly constant conditions, it would have ended up with smoother, mostly featureless basal surfaces.

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