{HEAD ~ an aggregate} of {TAIL ~ granular crystals} precipitated on said columnar crystals that has a hardness lower than that of the columnar crystals 
{ HEAD ~ an aggregate } of { TAIL ~ granular crystals } precipitated on said columnar crystals that has a hardness lower than that of the columnar crystals
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH