Corundum-bearing nodules and small lenses occur in layers about 30 cm thick in the dolomite marbles of the Vranga formation, constituting the upper part of the Shakhdara group. The nodules have a concentrically-zoned structure with a core up to 7 cm in the diameter, which consists of aggregates of pink, translucent corundum surrounded by amphiboles or spinel.
The size of corundum crystals ranges from several millimeters to 2 cm. Equidimensional or bladed near gem-quality crystals of pink to red colour are partially to completely transparent.
Ref: E.Ya. Kievlenko, Geology of gems, 2003, p. 54