Detecting forgeries among ancient gold objects using the U,Th-⁴He dating method

Forgeries of ancient gold objects are prevalent in almost every collection and some public exhibitions in the past have been exposed as containing forgeries to an embarrassing extent. This situation comes from the fact that it is sometimes impossible to unequivocally recognize forgeries based on their patina or manufacturing and decoration characteristics. We demonstrate that for 13 ancient gold objects the time of their last melting process can be estimated using the U,Th-⁴He dating technique. The extremely small quantities of radiogenic ⁴He found, due to the young age and small sample size, require the use of a specially designed ultrasensitive mass spectrometer. We show that the proposed method is a powerful, and the only, quantitative tool in archaeometry for discriminating between fake and genuine ancient gold objects.