Hemihedrite is a triclinic mineral having the composition ZnF2[Pb5(CrO4)3SiO4]2 with cell dimensions a = 9.497 Å, b = 11.443 Å, c= 10.841 Å, α = 120°30’, β = 92°06’,γ = 55°50’. Three-dimensional counter data were collected and the structure was solved from the Patterson function and refined to an R factor of 0.04. The structure is similar to those of the tsumebite series and contains a zinc coordinated by four oxygens and two fluoride ions; the lead environments are quite varied. Chromium and silicon are regularly four-coordinated by oxygen. Evidence from the crystal structure determination tends to cast some doubt on the morphological interpretation that the species is acentric.