Final Version Compose of several elements, The Snow flake is made of a blend shape animation, a Particle system that consist of mesh particles and fog, dust and sparkles. The last element is a destructible mesh.
Here is a breakdown of the particle system part.
This is the Material system. consist of several parts, includes z -depth animation for the cracking, and subsurface, fake reflection, and refraction.
This is my rough thumbnails animatic.