The investigation of mechanical characteristics was based on the calculations of elastic properties determined by performing finite distortions of the lattice and deriving the elastic constants (C ij ) from the strain-stress relationship. It is well-known that most of solids are polycrystalline and can be considered to a large extent as randomly oriented single-crystalline grains. Therefore, they may be described by bulk (B) and shear (G) moduli obtained by averaging the single-crystal elastic constants. The method used here is Voigt's which is based on a uniform strain. The calculated sets of elastic constants are given in Table for both 'glitter' and 'neoglitter'.