High-resolution transmission electron microscopy study of new orthorhombic boron-rich chalcogenides, B 6 S and B 6 Se, allowed us to identify microstructural features, typical for boron-rich solids synthesized at high pressures and high temperatures. It was found that twinning in both materials is realized in two planes: (101) and (002). Along with numerous twins on the (101) plane, two types of polytypes were found: ABAB stacking of B 12 icosahedra in both chalcogenides and AB 1 CD 1 AB 1 CD 1 stacking of B 12 icosahedra in B 6 Se. Shear bands and cracks have been found in {011} planes.