@chemicallyinsane : MDMA can form large crystals, the size of the crystal depends on the time it is given to form and the temperature.
when you have a batch of base mixed with i.e. dcm (a solvent) stirring at room temp, and you yank dry hcl gas thru it very fast, the solution will get hot and form small crystals as a powder.
When you have a mix of let's say acetone and base at -15C and you gas it carefully in an icebath until ph 6.5 is reached and you put it back into the freezer, the crystals that form can be really large.
it's the same when your windows freeze over in the winter. if the temp drop is gradual the flower like ice crystals (frozen water) will be large, whereas a rapid drop in temp forms smalll crystals.