The crystal growth of KNO3 (diamagnetism) has been investigated in a magnetic field of SO kOe. The crystallographic axes are determined bSi X-ray diffraction and compared with the magnetic axes. The crystals grow so that the magnetic chi(a) axis is perpendicular to the direction of the field. The orientation is explained by the magnetic susceptibility anisotropy (chi(a) < chi(b) similar to chi(c)) of the crystals. Since the magnetic energy has a minimum when the chi(a) axis is perpendicular to the field, the crystals containing a considerable number of unit cells can be stabilized by rotating in this direction against thermal disordering.