Abstract: Wooldridgeite, ideally Na2CaCu22+(P2O7)2(H2O)10, orthorhombic, a = 11.938(1), b = 32.854(2), c = 11.017(1) Å, V = 4321.2(8) ų, a:b:c = 0.3634:1:0.3353, space group Fdd2, Z = 8, is a new mineral from Judkins Quarry, Nuneaton, Warwickshire, England. Associated minerals are calcite, chalcopyrite, bornite and baryte. It occurs as equant crystals forming rhombic dipyramids; no twinning was observed. It is transparent blue-green with a very pale-blue streak, a vitreous lustre, and does not fluoresce under long- or short-wave ultraviolet light. Wooldridgeite has a Mohs hardness of 2–3, is brittle with an irregular fracture, and has no cleavage. The calculated density is 2.279 g/cm³. In transmitted light, wooldridgeite is colourless, non-pleochroic, and shows no dispersion. It is biaxial negative with α = 1.508(1), β = 1.511(1), γ = 1.517(1), 2V(meas.) = 76.2(5), 2V(calc.) = 71(10)°, X = b, Y = c, Z = a. The strongest five reflections in the X-ray powder diffraction pattern are [d(Å), (I), (hkl)]: 8.23(30)(040), 6.52(100)(131), 4.05(40)(260), 3.255(40)(262); 2.924(40)(371). Electron-microprobe analysis of wooldridgeite gave P₂O₅ 39.37, CuO 20.24, MgO 0.24, CaO 7.73, Na₂O 8.33, K₂O 0.17, H₂O(calc.) 24.72, sum 100.80 wt.%; the corresponding unit formula (based on 24 anions) is (Na_1.96K_0.03)Ca_1.00(Cu_1.85Mg_0.04)P_4.04O₁₄(H₂O)₁₀ where the H₂O groups were assigned from knowledge of the crystal structure; the infrared absorption spectrum also indicates the presence of H₂O in the structure. The mineral is named for James Wooldridge (1923–1995), a fervent amateur mineral collector who discovered this mineral.