Study of Some Uniaxial Minerals for Better Orientation of Faceting

For better manifestation of colours in anisotropic transparent stones the orientation of faceting along optical axes is necessary. Degree of absorption along and perpendicular to the main optical axis was studied for some uniaxial minerals, using several types of spectrophotometers. Tourmalines from Russian and American deposits, natural and synthetic rubies, blue beryls and apatites were measured. For all studied minerals the best orientation of faceting is recommended.