A triclinic polymorph of catena-poly[[diaqua­cobalt(II)]-μ-{μ-mellitato-κ²O¹:O⁴-bis­[penta­aqua­cobalt(II)]}-κ⁴O²,O³:O⁵,O⁶] hexa­hydrate]

A second, triclinic, polymorph of the title compound, {[Co₃(C₁₂O₁₂)(H₂O)₁₂]·6H₂O}_n, is reported. This polymorph forms a three-dimensional framework through O—H...O hydrogen-bond inter­actions between the one-dimensional [Co₃{C₆(COO)₆}₃(H₂O)₁₂]_n chains and the solvent water mol­ecules. The mellitate ligand lies on an inversion center.