Is dual morphology of rock-salt crystals possible with a single additive? The answer is yes, with barbituric acid.

Crystal face lift: barbituric acid is shown to be a new crystal-habit modifier for sodium chloride crystals. Two morphologies of salt crystals can be prepared separately with this new additive. It is of the few additives able to induce rhombic dodecahedron crystals for NaCl, and is required only a trace of amount, unlike other additives, such as glycine.