In the quartz-epidote tuff schist, from the Akmola region, there are voids filled either with quartz and epidote, or with turbid grains of feldspar. In the latter, epidote sometimes develops, replacing feldspar from the center to the periphery. One of these epidote grains, shown in the attached figure, exhibits zonal structure. The core of the grain, polarizing in 2nd-order yellow and distinctly pleochroic, is bordered by hexagonal zones of lower birefringence (blue and red), almost non-pleochroic; toward the periphery, only one sector remains with colorless layers of low birefringence. Withdifference in birefringence, all these zones simultaneously extinguish and brighten under crossed Nicols, especially clearly when observed in red light, which eliminates dispersion.