Optical rotatory power and depolarisation of light in the α-, incommensurate and β-phases of quartz (20 to 600 degrees C)

The rotator power of quartz and the polarisation rate of a linearly polarised light (6328 AA) were measured from 20 to 600 degrees C along the optical axis. In the region of the alpha -IC- beta transitions the variations in rotatory power are proportional to the variations in dilatation measured simultaneously. The IC- beta transition is marked by an angular point on the rotatory power variation curve, accompanied by a small depolarisation peak. A modulated depolarisation (on a slight birefringence), revealed by non-zero temperature scanning of the IC phase, appears over a small temperature range before the IC to alpha transition. A measurement of the effect of a uniaxial stress along the X direction is also given.