We report the first positive experimental observation of the optical a
ctivity effect on normal reflection. The experiment was performed alon
g the optic axis in a gyrotropic semiconductor crystal of alpha-HgS, c
innabar, in a spectral region of strong absorption. Reflected light po
larization azimuth rotation resulting from the reflection is of the or
der of 10(-4) rad and has pronounced dependence on HBARomega - E(g).