THE EFFECT OF STRAIN ON THE OPTICAL PROPERTIES OF QUARTZ: POINT-DIPOLE CALCULATIONS

Strained quartz commonly shows biaxial optical properties with 2V c up to ' 22 degrees . This research uses point -dipole theory to calculate the optical properties of a - quartz strained in various ways. Strain was modeled by distorting the lattice. Calculations that relate to simple a -axis compression involve decreasing the a -axis in small increments. Shear strain is modeled by altering the interaxial angles in small increments. The calculations agree with published experiments and observations on natural quartz tectonites. The methodology is transferable to other minerals. Point -dipole theory, as applied in this study, has the potential for quantifying the stress responsible for optical manifestations of strain in minerals. The strategy may be useful for designing laboratory experiments, understanding experimental results, and interpreting petrographic observations.