MgYS3 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 MgS6 octahedra that share corners with eight equivalent Y(1)S4 tetrahedra and edges with three equivalent Mg(1)S6 octahedra. Y(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form distorted YS4 tetrahedra that share corners with eight equivalent Mg(1)S6 octahedra and  an edgeedge with one Y(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-78°. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 3-coordinate geometry to two equivalent Mg(1) and one Y(1) atom. In the second S site, S(2) is bonded to two equivalent Mg(1) and two equivalent Y(1) atoms to form edge-sharing SY2Mg2 trigonal pyramids.
MgYS3 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 MgS6 octahedra that share corners with eight equivalent Y(1)S4 tetrahedra and edges with three equivalent Mg(1)S6 octahedra. Both Mg(1)-S(2) bond lengths are 2.52 Å. There are two shorter (2.54 Å) and two longer (2.89 Å) Mg(1)-S(1) bond lengths. Y(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form distorted YS4 tetrahedra that share corners with eight equivalent Mg(1)S6 octahedra and  an edgeedge with one Y(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-78°. Both Y(1)-S(1) bond lengths are 2.60 Å. There is one shorter (2.62 Å) and one longer (2.64 Å) Y(1)-S(2) bond length. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 3-coordinate geometry to two equivalent Mg(1) and one Y(1) atom. In the second S site, S(2) is bonded to two equivalent Mg(1) and two equivalent Y(1) atoms to form edge-sharing SY2Mg2 trigonal pyramids.