Hakite-(Cd), hakite-(Fe) and hakite-(Zn) are new minerals belonging to the tetrahedrite group and forming, along with hakite-(Hg), the hakite series. They have been discovered in samples collected from the Bytíz deposit, in the uranium and base-metal Příbram ore district, Central Bohemia, Czech Republic. They occur as anhedral grains, up to 300 μm in size, in a calcite gangue, associated with clausthalite, cadmoselite, hakite-(Hg) [for hakite-(Cd)], berzelianite, bukovite, bytízite, crookesite, chaméanite, eskebornite, příbramite, the not yet approved giraudite-(Hg) and giraudite-(Cu), hakite-(Hg), umangite, chalcopyrite, tetrahedrite-(Zn) and a new Cu–As selenide [for hakite-(Fe) and -(Zn)]. The three new species are black, with a metallic lustre. Mohs hardness is ca. 3½–4; calculated density is 6.019 (Hak-Cd), 6.011 (Hak-Fe) and 6.081 g.cm–3 (Hak-Zn). In reflected light, they are isotropic, pale grey with bluish (Hak-Cd) or brownish (Hak-Fe and Hak-Zn) shades. Empirical formulae of hakite-(Cd), hakite-(Fe), and hakite-(Zn) are Cu9.71Ag0.24Cd1.51Hg0.43Zn0.03(Sb3.94As0.13)Σ4.07Se11.35S1.57, Cu10.11Ag0.18Fe0.81Zn0.50Hg0.26(Sb3.72As0.41)Σ4.13Se12.65S0.12, and Cu10.03Ag0.24Zn0.61Fe0.53Hg0.45(Sb3.55As0.60)Σ4.15Se12.82S0.08, respectively. These formulae correspond to the end-member formulae Cu6(Cu4Cd2)Sb4Se13 (Hak-Cd), Cu6(Cu4Fe2)Sb4Se13 (Hak-Fe), and Cu6(Cu4Zn2)Sb4Se13 (Hak-Zn). All these new members of the hakite series are cubic, I$\bar{4}$3m, Z = 2, with unit-cell parameters a = 10.8860(6) Å, V = 1290.0(2) Å3 (Hak-Cd); a = 10.7983(4) Å, V = 1259.12(14) Å3 (Hak-Fe); and a = 10.8116(14) Å, V = 1263.8(5) Å3 (Hak-Zn). These species are isotypic with the other members of the tetrahedrite group, and their crystal structures have been refined on the basis of single-crystal X-ray diffraction data down to R1 values of 0.0230 (Hak-Cd), 0.0254 (Hak-Fe), and 0.0302 (Hak-Zn). These structural data allow us to describe the S-to-Se partitioning in hakite-series minerals and to understand the mechanisms avoiding too short Me–Se distances in these selenides.

The adsorption of Cu2+ on kaolinite was studied at different ionic strengths following various treatments of the mineral surface in order to evaluate the conditions influencing adsorption. The data indicate a strong preference of the Na+ exchange form of kaolinite for Cu2+ but a weak affinity of the natural kaolinite for Cu2+. Protons are generated by Cu2+ adsorption, a result of the exchange of surface protons, and possibly the enhancement of Cu2+ hydrolysis at the kaolinite surfaces. The exchange of Na+ by Cu2+ on the kaolinite is not described by the mass-action equation, but can be interpreted in terms of permanent charge sites on the surfaces when the additional factors of Na+-H3O+ exchange and blockage of sites by Al ions are considered.

This research aimed to examine the impact of varying levels of dietary copper (Cu) hydroxychloride on the performance, egg quality, yolk antioxidant capacity, tibia traits, and mineral excretion in laying quails. 125 female 10-week-old quails were randomly distributed into five experimental groups with five replicates, each consisting of five quails. Five experimental isonitrogenous and isoenergetic diets were designed to contain different Cu hydroxychloride (54% Cu) levels at 7.20 (basal diet), 15, 30, 45 and 60 mg/kg respectively. Quails were fed with trial diets for 12 weeks. Performance, egg production, eggshell quality, and biomechanical traits of the tibia were not impacted (P > 0.005) by variations in dietary Cu levels. Yolk antioxidant capacity, measured as yolk DPPH value, exhibited an increase (P < 0.01) in the high-dose group (60 mg/kg). Regarding tibia mineral concentration, Cu concentration decreased linearly (P < 0.001) with increasing Cu level, manganese and zinc content recorded the highest values in quails that had received 60 mg/kg Cu in the diet (P < 0.01), while the lowest phosphorus content was described for 45 and 60 mg/kg. Contrarily, increases (P < 0.01) in dietary Cu resulted in raised faecal Cu content, while phosphorus, manganese, and zinc, were reduced when Cu was added. It can be inferred that adding Cu to the diet of laying quails would not be necessary, which in turn decreases Cu excretion and prevents substantial environmental harm.

Tetrahedrite-(Cu), Cu12Sb4S13, has been approved as a new mineral species (IMA2022–078) from the Bankov magnesite deposit near Košice, Slovak Republic where it occurs as anhedral grains, up to 0.4 mm across, associated with skinnerite, chalcostibite, famatinite, tetrahedrite-(Fe) and zoned aggregates of tennantite-(Cu) to tennantite-(Fe). Tetrahedrite-(Cu) is steel-grey, with a metallic lustre. Mohs hardness is ca. 3½–4 and calculated density is 5.029 g.cm–3. In reflected light, tetrahedrite-(Cu) is isotropic and grey with a bluish shade. Reflectance data for the four COM wavelengths in air are [λ (nm): R (%)]: 470: 31.1; 546: 30.1; 589: 29.9; and 650: 28.1. The empirical formula, based on electron-microprobe data (mean of 17 spot analyses), is Cu11.42Zn0.26Fe0.19(Sb4.06As0.08)Σ4.14S12.99. The ideal formula is Cu6(Cu4Cu2)Sb4S13, which requires (in wt.%) Cu 45.76, Sb 29.23 and S 25.01, total 100.00. Tetrahedrite-(Cu) is cubic, I$\bar{4}$3m, with unit-cell parameters a = 10.3296(15) Å, V = 1102.2(5) Å3 and Z = 2. Its crystal structure was refined by single-crystal X-ray diffraction data to a final R1 = 0.0347 on the basis of 261 unique reflections with Fo > 4σ(Fo) and 22 refined parameters. Tetrahedrite-(Cu) is isotypic with other tetrahedrite-group minerals. Previous findings of tetrahedrite-(Cu) are reported and some nomenclature issues, related to the Fe and Cu oxidation states, are discussed. At the Bankov deposit, tetrahedrite-(Cu) is related to hydrothermal, most probably Alpine, solutions strongly enriched in Cu, Sb and S.

Electron spin resonance (ESR) spectra of Cu2+-hexadecylpyridinium (HDP) montmorillonites were investigated as a function of HDP+ content and the hydration state of Cu2+ at relative humidities of p/p0 = 0.52-8 × 10-7 at 298°K. The symmetry of the Cu2+ ESR spectra and the intensity of the ESR signal increased upon dehydration of the complex. The HDP+ cation caused an increase in the hydration state of Cu2+ at a given p/p0 and an increase in the covalency of the Cu-O bond.

The adsorption of D-glucosamine (2-amino-2-deoxy-D-gIucose) in the protonated or neutral form on homoionic Cu2+-bentonite was investigated by infrared (IR) and electron spin resonance (ESR) spectroscopy and chemical analyses of solution. The results show that the interaction of the glucosamine hydrochloride with the clay complexed a small fraction of interlayer metal ions with neutral amino sugar molecules. In contrast, the adsorption of free glucosamine was much more favorable and resulted in interlayer copper(II) complexes, mainly those in which the ligand was coordinated through amino and deprotonated hydroxyl groups. Part of the amino sugar molecules, however, were transformed into glucosammonium, replacing copper as the saturating ion.

The ferrous iron content of two vermiculitized biotites decreased by treatment with 0.1 N salts of copper at 70°C from 9.1–14% to 1.8–2.6%. Presumably, interlayer copper ions acted as a catalyst (here, an electron carrier) for the oxidation of iron by dissolved oxygen. The oxidized iron was ejected from the structure and formed crystalline iron minerals, such as hematite and goethite. Weight loss determinations, chemical, and X-ray powder diffraction data suggest that Cu(II) ions were polymerized to hydroxy-hydrous compounds in the interlayer space. Poor exchangeability of the resultant complex is attributed to the formation of strong electrostatic attractions between OH groups of the interlayer complexes and silicate oxygens.

Electron spin resonance (ESR) analysis of Cu2+-hectorite suspensions provides evidence for the surface-induced hydrolysis of Cu(H2O)62+ at low pH and surface-inhibited hydrolysis (or precipitation) at high pH. Dehydration of the hectorite by heating to 110°C appears to promote hydrolysis in high pH clays further. Heating to even higher temperatures removes ligand water from Cu2+, allowing the metal ion to coordinate with silicate oxygen atoms. The planar Cu(H2O)42+ ion predominates in the interlamellar regions of hectorite that has been air dried or heated to temperatures of 110°C or lower, but more extreme thermal treatment changes the apparent orientation of the Cu2+-ligand axes as some or all of the four water ligands are removed, A loss in ESR signal intensity upon heating Cu2+-hectorite above 110°C is evidence for lowered symmetry of the dehydrated, surface-coordinated Cu2+ ion.

The adsorption of Cu2+ on microcrystalline gibbsite and boehmite from aqueous solutions having 2/1 and 5/1 glycine/Cu ratios has been studied using electron spin resonance (ESR). The presence of glycine inhibited metal adsorption on gibbsite above pH 5, apparently by reducing Cu hydrolysis. The preferred adsorbed species on gibbsite and boehmite, based upon the ESR parameters, were probably Cu(gly)+ and Cu(gly)20, respectively. In both experiments, rigidly-bound ternary complexes formed with Cu2+ simultaneously bonding to the surface and one or more ligands. A large excess of glycine destabilized the ternary complex and caused the desorption of Cu2+. The preferred orientation of the Cu complex on gibbsite suggests that the adsorption occurred at crystal steps and that the glycine molecule hydrogen bonded to hydroxyls of the (001) surface.

The reaction of benzene with exchangeable Cu(II) and Fe(III) in hectorite clay films was studied by electron paramagnetic resonance (EPR). The reaction when carried out in a sealed tube between 60° and 100°C produced a variety of organic radical products. The nature of these products depended on the concentration of water in the reaction medium and the reaction time. The free radicals were accompanied by a reduction in the oxidation state of the metal ions; this process had a zero-order dependence on the metal ion concentration. The activation energies determined from the zero-order rate constants are 67 ± 11 kJ/mole (Cu(II)) and 46 ± 6 kJ/mole (Fe(III)). The free radicals initially formed under anhydrous conditions appeared to populate sites in the interlayer region; the activation energies determined for this first order process are 57 ± 9 kJ/mole (Cu(II)) and 42 ± 3 kJ/mole (Fe(III)). These activation energies are within experimental error of those determined from the metal ion kinetics. The EPR signal due to organic radicals showed little temperature dependence; thus, exchange processes involving organic free radicals were probably not important in determining EPR lineshapes.

Copper adsorption on a hydroxy-aluminum-hectorite complex (OH-Al-hectorite) at pH 4.5, 5.7, 7.4, and 7.8 was examined by means of electron spin resonance. The spectra of these samples were compared to those of Cu2+-hectorite and various aluminum hydrous oxides. Copper on the OH-Al-hectorite in aqueous gels occurred as mobile Cu(H20)62+ and chemisorbed to discrete sites of the OH-Al interlayer. As pH was increased, the ratio of chemisorbed to mobile Cu2+ increased. At pHs above 7 the solubility product of Cu(OH)2 was exceeded, but chemisorbed Cu2+ remained as the dominant species. These results contrast with the precipitation of Cu observed on microcry stalline gibbsite above pH 5 and indicate that the interlayer OH-A1 retained more Cu2+ on discrete sites. The greater adsorption capacity probably resulted in part from a higher specific surface area. Electron spin resonance spectra of Cu2+ in air-dried films of the OH-Al-hectorite at pH 4.5 and 7.4 showed Cu2+ in square planar symmetry, oriented with the z-axis perpendicular to the OH-Al-hectorite a-b plane. At the higher pH, the spectrum resembled that of Cu(OH)42- on alumina, suggesting a ligand exchange mechanism for Cu2+ adsorption on the complex.

The ability of a high surface-area gibbsite to adsorb Cu2+ was studied using a Cu2+ ion-selective electrode, electron spin resonance, infrared spectroscopy, and electron microscopy. The gibbsite chemi-sorbed small amounts of monomelic Cu2+ (<0.5 mmole/100 g) which was oriented with its z-axis perpendicular to the (001) plane of the mineral. The proposed chemisorption sites are at gibbsite crystal “steps” observed by electron microscopy. Although Cu2+ adsorption on gibbsite as a function of pH was largely reversible, exposure of the chemisorbed Cu2+ to NH3 did not result in desorption from the surface despite the displacement of several OH− or H2O ligands by NH3. The results indicate that at least one Cu-O-Al bond is formed in the process of chemisorption.

At pH > 5, the gibbsite appeared to promote the hydrolysis and polymerization of Cu2+, with further adsorption at the surfaces. Infrared spectroscopy revealed no effect of the adsorption on the (001) surface hydroxyl groups, although the anisotropic diffusion of protons in the gibbsite structure was verified from deuteration studies.

Adsorption of Cu2+ and Co2+ by synthetic imogolite, synthetic allophanes with a range of SiO2/ Al2O3 ratios, and allophanic clay fractions from volcanic ash soils was measured in an ionic medium of 0.05 M Ca(NO3)2. The effect of pH (and metal concentration) on adsorption was qualitatively similar for the synthetic and natural allophanes with relatively minor changes in behavior caused by variable SiO2/Al2O3 ratios. Cu and Co were chemisorbed by allophane at pH 5.0–5.5 and 6.9–7.2 (pH values for 50% adsorption level), respectively, with concomitant release of 1.6–1.9 protons/metal ion adsorbed. Quantitatively, adsorption by imogolite was less than that by the allophanes, presumably because of fewer sites available for chemisorption on the tubular structure of imogolite. Electron spin resonance studies of the imogolite and allophanes revealed that Cu2+ was adsorbed as a monomer on two types of surface sites. The preferred sites were likely adjacent AlOH groups binding Cu2+ by a binuclear mechanism; weaker bonding occurred at isolated AlOH or SiOH groups. These chemisorbed forms of Cu2+ were readily extracted by EDTA, CH3COOH, and metals capable of specific adsorption, but were not exchangeable. In addition, the H2O and/or OH− ligands of chemisorbed Cu2+ were readily displaced by NH3, with the formation of ternary Cu-ammonia-surface complexes.

The nature of Cu2+ adsorption by boehmite, gibbsite, and noncrystalline alumina was studied over a range of equilibrium pH (4.5–7.5) and Cu2+ concentration (10−3–10−8 M) by electron spin resonance (ESR). Available chemisorption sites at pH 4.5 were the most numerous for noncrystalline alumina (~1 mmole/100 g), less for boehmite, and least for gibbsite as indicated by the relative strength of the rigid-limit ESR signal attributed to Cu2+ adsorbed at discrete sites. The chemisorption process involved immobilization of Cu2+ by displacement of one or more H2O ligands by hydroxyl or surface oxygen ions, with the formation of at least one Cu-O-Al bond. As the pH was raised from 4.5 to 6.0, essentially all of the solution Cu2+ appeared to be adsorbed by the solids. However, the noncrystalline alumina and boehmite chemisorbed much of the total adsorbed Cu2+ (10 mmole/100 g), whereas precipitation or nucleation of Cu(OH)2 in the gibbsite system was indicated. Precipitated Cu2+ was more readily redissolved by exposure to NH3 vapor than chemisorbed Cu2+.

Weathering of a copper stratiform deposit (schist) at Salobo, Brazil, has produced two distinct Cu-bearing minerals from a biotite parent: vermiculite and a manganese oxide containing as much as 13% and 25% CuO, respectively. Manganiferous products were formed as the result of an interhorizon transfer of solutions through a fissure system. Thus, the structural orientation of the schists was a major factor in controlling the supergene concentration of Cu. The Cu-vermiculite formed by the weathering of Fe-biotite, although the unweathered biotites in the parent rocks were found to contain no copper, suggesting that Cu was supplied by weathering solutions. X-ray powder diffraction (XRD) and cationexchange capacity data for the Cu-vermiculite differ from those of typical Mg-vermiculite and are similar to those of hydroxy- Al-vermiculite. A comparison of the XRD pattern of the Cu-vermiculite with that of a Cu-free vermiculite indicates that Cu atoms are located in interlayer sites. Cu probably occurs in a brucite-like layer. The position and structure of the Cu K-absorption spectrum suggest that the Cu is divalent and exists in 6-fold coordination.

Watanabeite from the Pefka epithermal deposit, northeastern Greece, was examined using single-crystal X-ray diffraction and electron microprobe analysis. The empirical formula of watanabeite is Cu3.93Fe0.10Ag0.01Pb0.23As1.55Sb0.19S4.99. This mineral is orthorhombic, space group Amm2, with unit-cell parameters a = 10.9601(5), b = 14.6498(8), c = 10.3001(5) Å, V = 1653.82(14) Å3 and Z = 8. The crystal structure was solved and refined to R1 = 0.0471 for 2108 unique reflections with Fo > 4σ(Fo) and 123 refined parameters. The crystal structure of watanabeite can be described as a three-dimensional framework of Cu-centred tetrahedra; cavities of the tetrahedral scaffolding host Cu6S and As2(Pb,Sb,As)2S7 clusters. On the basis of structural data, the formula of watanabeite could be written as [III]Cu3[IV]Cu5As3(Pb,Sb,As)S10 (Z = 4), considering the three independent three-fold Cu sites and the three independent tetrahedrally coordinated Cu sites as aggregated positions. The occurrence of Pb2+ in watanabeite is probably related to the substitution Cu+ + (As,Sb)3+ = 2Me2+, where Me = Pb, Fe, Zn and formally divalent Cu. The relationships with tetrahedrite-group minerals are discussed on the basis of the refined structural model, highlighting possible crystal chemical implications of such relationships.