Tsumcorite belongs to the monoclinic crystal class 2/m, which means that it has a twofold axis of symmetry along the b axis and a mirror plane perpendicular to this, in the plane containing the a and c axes. The a and c axes are inclined to each other at angle β = 115.3°. The unit cell parameters are a = 9.124 Å to 9.131 Å, b = 6.326 Å to 6.329 Å and c = 7.577 Å to 7.583 Å.[1][2][3][5] There are two formula units per unit cell (Z = 2), and the space group is C2/m, meaning that the cell is a C-face centred lattice, with lattice points in the center of the C face as well as at the corners of the cell.[7] The structure is related to the brackebushite group structure.[1]