I'm trying to figure out how to procedurally model bismuth crystals, but I'm kind of a noob at Houdini. Any ideas on how I might do this?

For reference, I HAVE determined the rules of hopper crystal growth, which are as follows:

-layers grow on the exposed edges of the existing crystal
-layers do not grow on the "inner surface" of the hopper
-layers can be different thicknesses, but always grow up and out at a 45-degree angle
-outer edges never intersect each other perfectly
-all edges that do not form a closed loop end in an inward turn
-no convex corner edges are exposed
-the inner termination points of spiral structures either extend inwards until they contact another surface or curve inwards to form a spiral on a different plane
-all spirals turn inwards
-incomplete edges can form on inside layers
-non-rectangular closed edges can exist (but all edges must still be at right angles)

John Kunz had a livestream on this topic: