Analytical studies on pre-Columbian gold and silver from the North of Peru

Portable devices for energy-dispersive X-ray fluorescence analysis and X and γ-ray transmission measurements were employed to analyze pre-Columbian metals from the North of Peru. Gold and silver are generally composed of gold, silver, and copper and silver, copper, and gold (and more rarely lead), respectively. Besides gold and silver, artisans from these cultures also produced artifacts with gilded copper, gilded silver, tumbaga (gold alloys enriched at the surface by depletion gilding), silvered copper, and silvered gold. Furthermore, “strange” elements like arsenic, bromine, and mercury were also sometimes detected by energy-dispersive X-ray fluorescence, rarely in gold alloys (mercury) and more frequently in silver alloys (arsenic, bromine and mercury). Arsenic is associated with copper, always present in silver alloys, while bromine and lead are typically associated to silver. Finally, mercury, in form of cinnabar powder, was employed to cover gold masks, and, possibly in form of liquid mercury, for a process called “mercury amalgam” to sold together gold and silver sheets.