Phys.org September 2, 2024 Gold nuggets occur predominantly in quartz veins, and the current paradigm posits that gold precipitates from dilute (<1 mg kg−1 gold), hot, water ± carbon dioxide-rich fluids owing to changes in temperature, pressure and/or fluid chemistry. However, the widespread occurrence of large gold nuggets is at odds with the dilute nature of these fluids and the chemical inertness of quartz. Using quartz deformation experiments and piezoelectric modelling researchers in Australia investigated if piezoelectric discharge from quartz could explain the ubiquitous gold–quartz association and the formation of gold nuggets. They found that stress on quartz crystals could generate enough voltage to […]
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Striking rare gold: Researchers unveil new material infused with gold in an exotic chemical state
Phys.org September 30, 2023 Although Cu2+ is ubiquitous, the relativistic destabilization of the 5d orbitals makes the isoelectronic Au2+ exceedingly rare, typically stabilized only through Au–Au bonding or by using redox non-innocent ligands. An international team of researchers (USA – Stanford University, UC Berkeley, SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory, Canada) have developed the perovskite Cs4AuIIAuIII2Cl12, an extended solid with mononuclear Au2+ sites, which is stable to ambient conditions and characterized by single-crystal X-ray diffraction. The 2+ oxidation state of Au was assigned using 197Au Mössbauer spectroscopy, electron paramagnetic resonance, and magnetic susceptibility measurements, with comparison to paramagnetic […]