It is highly unlikely that you’ll find two identical snowflakes. Feel free to try to prove us wrong, but your search may involve some cold feet! If you compared 1 million snowflakes (a minuscule fraction of the flakes in a single snowstorm), performing two comparisons per second, you’d need about 100,000 years!

A simple snowflake is a single ice crystal, but most flakes are an aggregation of a group of ice crystals. Ice crystals are six-sided and come in four basic shapes: column, needle, hexagonal plate and dendrite. The shape in which an ice crystal grows depends on the air temperature around it. As a crystal moves through a cloud it continually encounters different temperatures, which continually modify its shape. Crystals also hit other crystals and break, chip or crack, further altering their shape.

You might be able to find two similar shapes of the initial crystals, but they will be hard to locate in the cloud. Maybe it’s better to just stand in a snowfall and enjoy their beauty rather than look for twins! Or view wonderful photos of ice crystals at The Bentley Collection.

Photo of snow in west Sierra Nevada by Itrovert

Sometimes on a sunny day, freshly fallen snow may appear to sparkle or glitter. This happens because when light hits an object light, it can be absorbed, in which case the object is heated; transmitted, in which case light passes through the object; or reflected, in which case it bounces back.

Clear water can transmit or reflect light (think of how a calm lake can reflect an image of the trees on the shoreline). Flat snowflakes resting on top of a blanket of snow also can act like a mirror, reflecting a portion of the sun’s image toward your eye. Each ‘sparkle’ is a reflection of the sun’s image from a single crystal. Whether we see the sparkle depends on the angle between the sun, the snowflake’s position on the snow and the location of our eye. When the angle is right, when we walk by a field of snow, we’ll see glitter as the sun is reflected by different snowflakes.

You may notice some faint colors in the sparkles. As light travels between air and water, the colors in the light separate, much as they do in a rainbow. The sun’s ray can reflect off different surfaces of the crystal. If the sunlight reflects off the back of the ice crystal, the colors may disperse as the light enters and exits the crystal, making those faint colors.

Humidity — water vapor pressure in the cloud — affects the growth rate due to deposition. A flake that passes through dry air may sublimate (lose mass by converting from solid to gas).

Because temperature and humidity change as a flake bounces around in a cloud, the basic shapes can blend into countless crystal shapes. An ice crystal may also collide with another crystal and aggregate into a snowflake of a different shape. Or crystals may grow as they accrete (collide and adhere) tiny drops of liquid water in the cloud.