MgDyS3 is Ilmenite-like structured and crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form distorted MgS6 octahedra that share corners with four equivalent Dy(1)S6 pentagonal pyramids, edges with three equivalent Mg(1)S6 octahedra, and edges with four equivalent Dy(1)S6 pentagonal pyramids. Dy(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form distorted DyS6 pentagonal pyramids that share corners with four equivalent Mg(1)S6 octahedra, edges with four equivalent Mg(1)S6 octahedra,  an edgeedge with one Dy(1)S6 pentagonal pyramid, and  a faceface with one Dy(1)S6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 38-48°. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 4-coordinate geometry to two equivalent Mg(1) and two equivalent Dy(1) atoms. In the second S site, S(2) is bonded to two equivalent Mg(1) and two equivalent Dy(1) atoms to form edge-sharing SDy2Mg2 trigonal pyramids.
MgDyS3 is Ilmenite-like structured and crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form distorted MgS6 octahedra that share corners with four equivalent Dy(1)S6 pentagonal pyramids, edges with three equivalent Mg(1)S6 octahedra, and edges with four equivalent Dy(1)S6 pentagonal pyramids. Both Mg(1)-S(2) bond lengths are 2.53 Å. There are two shorter (2.56 Å) and two longer (2.94 Å) Mg(1)-S(1) bond lengths. Dy(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form distorted DyS6 pentagonal pyramids that share corners with four equivalent Mg(1)S6 octahedra, edges with four equivalent Mg(1)S6 octahedra,  an edgeedge with one Dy(1)S6 pentagonal pyramid, and  a faceface with one Dy(1)S6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 38-48°. There is one shorter (2.69 Å) and one longer (2.70 Å) Dy(1)-S(2) bond length. There are two shorter (2.67 Å) and two longer (2.93 Å) Dy(1)-S(1) bond lengths. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 4-coordinate geometry to two equivalent Mg(1) and two equivalent Dy(1) atoms. In the second S site, S(2) is bonded to two equivalent Mg(1) and two equivalent Dy(1) atoms to form edge-sharing SDy2Mg2 trigonal pyramids.