The shape of snowflakes is very large, but how are all kinds of snowflakes formed? Most snowflakes are hexagonal, which is because snowflakes belong to the six-square crystal system. Snowflakes in the cloud "embryo" small ice crystals, there are two main shapes. A hexagonal body-shaped, long and thin, called columnar, but sometimes its ends are pointed, like a needle, called Needle crystal. The other is a hexagonal flake, like a slice cut from a six-sided pencil, called a wafer.
If the ambient air is too saturated, the ice crystals grow very slowly and each side grows evenly. When it increases in descent, it still retains its original appearance, called Columnar, needle-shaped, and flake-like crystals.
If the ambient air is highly saturated, the ice crystals will not only increase in volume but also change in shape. The most common is the flake into a star shape.
It turns out that the water vapor near the ice crystals will be consumed at the same time as the ice crystals grow. Therefore, the closer to the ice crystals, the thinner the water vapor, the lower the saturation degree. Near the surface of the ice crystals, because the excess water vapor has been sublimation on the ice crystals, so just reached saturation. In this way, the vapor density near the ice crystal will be smaller than the distance from it. The water vapor moves from the ice crystals around the ice crystals. Water vapor molecules first encounter the various angular and protruding parts of ice crystals, and here sublimation and make ice crystals grow. The various angular edges and projections of the ice crystals will first grow rapidly, and gradually become branches and forks. Later, again because of the same reason in each branch and corner of the director of the new branchlets of the fork. At the same time, in the depressions between the corners and the branches. The air is no longer saturated. Sometimes, there are even sublimation processes where water vapor is transported to other places. This makes the corners and forks more prominent, and slowly forms the familiar star-like snowflakes.
What is said above is actually a typical star-shaped snowflake formation process. Its parts, regardless of shape or size, should be the same. This typical star-shaped snowflake can only be formed in an ideal, tranquil environment, such as in a laboratory. In the atmosphere, it can not be as described above the steps of the increase, the shape of the form can not be so typical. This is because the ice crystals gradually decline, and sometimes rotate, the various branches contact the water vapor is different, and those who are more exposed to water vapor more growth. As a result, the snowflakes we usually see are basically the same but different.
In addition, snowflakes fall in the cloud in the process, also from the appropriate to form the shape of the environment to the formation of another shape suitable for the environment, and then out of a variety of complex snowflake shape. Some like cufflinks, some like shotguns. Even a star-like Snowflake, there are three branches, six branches, and even 12 branches, 18 branches.