Comparative crystal habit study of quartz and MPO4 isomorphous compounds (M = Al,Ga)

Comparative investigation of the crystal habit of -quartz and two quartz-like materials (AlPO₄ and GaPO₄) has been undertaken on the basis of the Bravais-Friedel-Donnay-Harker (BFDH) law and the Hartman-Perdock (PBCs) theory. Unlike to these predictions, very strong morphological differences are observed. The crystal habit changes can be expressed in terms of crystal structure distortions and extrinsic parameters such as: temperature, pressure, solvent and impurities of the crystal growth experiments. All these parameters are not independent from one another, so only a qualitative explanation can be given.