Results of non-destructive analyses of solders on more than 300 items of antique gold jewellery artifacts involving the irradiation of the material with protons and the prompt detection of X-ray signals allow a better understanding of the joining procedures used by ancient goldsmiths. An unconventional interpretation of the 33rd Book, Natural History, of Pliny the Elder (1st century, AD) concerning chrysocolla (or gold solder) sheds some light on the current debate concerning the possible use in antiquity of greenockite (natural CdS) as a material alloyed with gold to achieve low melting point brazing. Figures, results of PIXE analyses, 18 bibliographic references.