Star and plate snowflake, light micrograph. Snowflakes are ice crystals that form in air that has a temperature near the freezing point of water. If the air is calm, then a symmetrical, hexagonal snowflake can form. The two main growth patterns observed are faceting and branching. When growth is fast and unstable, branching patterns create a dendritic snowflake. Slower growth allows the straight lines and hexagonal shapes of a plate snowflake. Here, a plate core is followed by the arms of a simple star snowflake, with plate formation later resuming at the apexes of the snowflake.