ELASTIC LIGHT-SCATTERING AND BIREFRINGENCE MEASUREMENTS IN THE COEXISTENCE STATE OF ALPHA-QUARTZ AND BETA-QUARTZ

New optical measurements of light scattering in the heterophase structure produced by the coexistence of α and β phases in quartz around 573°C, with simultaneous observations by optical microscopy, are presented. The heterophase structure variations are described in a heating and cooling temperature cycle with the two phases always remaining in the crystal. Nucleations of one phase in the other are observed, and the associated effects on right angle and small angle scatterings are presented. Birefringence in the plane perpendicular to the optical axis was measured as a function of temperature and position in the crystal, showing clearly the existence of induced stresses in the heterophase state. © 1979.