The 6 sided geometric symmetry observed within snowflakes is governed by the rigid molecular structure of hexagonal ice, which is the only crystalline form water can adopt within the Earth’s atmosphere, and the reason snowflakes always have 6 dendrites (points) like a hexagon. It is a common misconception that all snow crystals (snowflakes) exhibit perfect symmetry, as most often they do not possess this characteristic. It is true in the sense that at the microscopic molecular scale, snow crystals form perfectly, but it is untrue because at the macro, real world scale, anomalies virtually always form. This occurs because as the snow crystal becomes larger, water molecules no longer attach to develop and maintain a uniform orientation. Additionally, as the snow crystal grows and expands, factors of the ambient environment begin to influence it (e.g. effects of humidity and temperature etc.) causing the snow crystal to grow one way whilst in one position of a cloud and then grow in a completely different orientation once having been forcibly moved to a different spot within that same cloud. Because of this, it is rare but still possible to find a perfectly symmetrical snowflake. This explains why despite the complex and random nature of snow crystal growth, all 6 arms must align in every case and grow along the same 6 fixed 60 degree axes. If this does not occur, the snow crystal would violate the fundamental laws of energy minimization (to become most stable) dictated by the hydrogen bond lattice (framework connecting atoms within water), which would cause the structure of the snow crystal to become thermodynamically unstable and therefore highly prone to fracture
