Four polymorphs of Zn(OH)₂ have now been recorded from an oxidised vein exposure near Milltown, Ashover, Derbyshire; sweetite, wülfingite, γ-Zn(OH)₂, and ashoverite. The last is a new mineral, a tetragonal modification of Zn(OH)₂ containing minor quantities of Pb, Cd and Ca. Its unit cell dimensions are a 6.825(2) and c 33.36(4) Å, giving V = 1554 ų; Z = 32; space group I4₁/amd, I4₁ md, or I4¯2d; D_meas. 3.3, D_calc 3.44 g cm⁻³. Ashoverite occurs as colourless platy crystals associated with fluorite; it is uniaxial positive with ω 1.629(2), ε 1.639(2). The chemical composition of sweetite is compared with that of ashoverite.