Basic setup with color driving a foreach for scaling and extruding a hexagonized mesh. Using this on a more complex mesh, you will likely go a bit nuts tweaking away overlapping crystals.
Oh, and this is a viewport playblast but I played around with it a bit in Fusion, added some motion blur and what not, also playing around with exporting alembic from Houdini, importing it into Fusion. And this is actually the first composite I ever rendered out of Fusion. :D
Updated scene file: bit.ly/houdinicrystalgrowth (H16)
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