Fractionation factors for the isotopes of O, H, S, or Cu (as appropriate) were determined for the minerals brochantite [Cu4(SO4)(OH)6], libethenite [Cu2(PO4)(OH)] and olivenite [Cu2(AsO4)(OH)] and corresponding aqueous solutions at temperatures between 30 and 70°C. All samples used for this determination were synthetic and the degree of fractionation was expressed as 1000 ln α = (A × 106/T2) + B, where A and B are empirical parameters. A few natural libethenite samples from its type locality Ľubietová-Podlipa were also analysed and compared to the prediction based on the isotopic composition of meteoric water and our fractionation factors. The hydrogen fractionation factors agreed with the prediction well, whereas those for oxygen did not. A possible explanation is the disequilibrium of aqueous phosphate (and also arsenate) species and the solution in our experiments or the interaction of meteoric fluids with the isotopically heavy (in terms of oxygen) country rocks. Because the effects of isotopic disequilibrium in our experiments cannot be ruled out, the oxygen fractionation factors should be used with caution. The determined fractionation factors can be used as an isotope geothermometer, given that it can be proven that the phases of interest precipitated from the same fluid in equilibrium. Libethenite is predicted to have slightly lower δ65Cu values than its parental solution, but brochantite slightly higher δ65Cu values than its parental solution. Simple forward models, simulating neutralisation or reduction of mine drainage, show that precipitation of these minerals and removal of the co-existing fluid, could cause isotopic variations (in δ65Cu) on the order of 1‰ or more.

The free energies of formation of the minerals libethenite, Cu2PO4OH, pseudomalachite, Cu5(PO4)2(OH)4, cornetite, Cu3PO4(OH)3, tarbuttite, Zn2PO4OH, spencerite, Zn2PO4OH · 1.5H2O, and scholzite, CaZn2(PO4)2 · 2H2O, have been determined at 298.2 K using solution techniques. The values of ΔfG° (298.2 K) for the above minerals are, respectively, −1228.8±3.0, −2840.3±4.2, −1600.9±5.9, −1632.1±4.0, −1982.4±3.1, and −3556.7±7.6 kJ mol−1. These results, together with others from the literature concerning hopeite, Zn3(PO4)2·4H2O, hydroxyapatite, Ca5(PO4)3(OH), and the synthetic salt Cu3(PO4)2 · 2H2O have been used to construct a model for the formation of suites of Zn(II) and Cu(II) phosphate minerals found in the oxidation zone of base metal orebodies. The distributions and modes of occurrence of many natural assemblages of these minerals are readily explained by the model. Particular attention has been focused on deposits at Broken Hill, Zambia, and Saginaw Hill, Arizona, USA.

The structural modifications with temperature of libethenite, Cu2(PO4)(OH), were determined by single-crystal X-ray diffraction up to dehydration and consequent decomposition of the crystal under investigation. In the temperature range 25–475°C, libethenite shows positive and linear expansion. The axial thermal expansion coefficients, determined over this temperature range, are: αa = 6.6(1)·10–6 K–1, αb = 1.21(2)·10–5 K–1, αc = 9.0(2)·10–6 K–1, αv = 2.78(3)·10–5 K–1. Axial expansion is then anisotropic with αa:αb:αc = 1:1.83:1.33.

Structure refinements of X-ray diffraction data collected at different temperatures allowed us to characterize the mechanisms by which the libethenite structure accommodates variations in temperature. Increasing temperature induces expansion of both Cu polyhedra and no significant variation of the PO4 tetrahedron, which acts as a rigid unit. Cu(1) octahedra expand mostly as a consequence of the increase of the axial bonds, and become more distorted. Starting from T = 500°C, precursor signs of incoming dehydration are visible: two adjacent OH groups approach each other and cause dramatic changes in the whole structure. Concomitantly, the libethenite crystal begins to deteriorate and, at T = 600°C, broad and weak diffraction effects of polycrystalline material are observed.

Tiny green crystals from Kabwe, Zambia, associated with hopeite and tarbuttite (and probably first recorded in 1908 but never adequately characterized because of their scarcity) have been studied by X-ray diffraction, microchemical and electron probe microanalysis, infrared spectroscopy, and synthesis experiments. They are shown to be orthorhombic, stoichiometric CuZnPO4OH, of species rank, forming the end-member of a solid-solution series to libethenite, Cu2PO4OH, and are named zincolibethenite. The libethenite structure is unwilling to accommodate any more Zn substituting for Cu at atmospheric pressure, syntheses using Zn-rich solutions precipitating a mixture of zincolibethenite with hopeite, Zn3(PO4)2.4H2O. Single-crystal X-ray data confirm that the Cu(II) occupies the Jahn-Teller distorted 6-coordinate cation site in the libethenite lattice, and the Zn(II) occupies the 5-coordinate site. The space group of zincolibethenite is Pnnm, the same as that of libethenite, with unit-cell parameters a = 8.326, b = 8.260, c = 5.877 Å , V = 404.5 Å 3, Z = 4, calculated density = 3.972 g/cm3 (libethenite has a = 8.076, b = 8.407, c = 5.898 Å , V = 400.44 Å 3, Z = 4, calculated density = 3.965 g/cm3). Zincolibethenite is biaxial negative, with 2Vα(calc.) of 49°, r<v, and α = 1.660, β = 1.705, and γ = 1.715 The mineral is named for its relationship to libethenite.