This SciAm article ( <a href="http:&#x2F;&#x2F;www.scientificamerican.com&#x2F;article&#x2F;why-do-snowflakes-crystal&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.scientificamerican.com&#x2F;article&#x2F;why-do-snowflakes-...</a> ) helped me. It&#x27;s hard to summarize, but it looks like branching starts (in certain conditions) on corners and amplifies existing projections. Corners start hexagonally symmetrical, and to the extent that the formation of &quot;dendrites&quot; proceeds in lockstep around the crystal (due to uniform conditions?), they stay symmetrical. The amplification effect is weaker for the smaller sub-branches, so those are somewhat but not always symmetrical.<p>It doesn&#x27;t help that there&#x27;s a couple missing diagrams, but I think the first one is just a hexagonal prism and I didn&#x27;t really need the second.