The main objective of the former Metalor project consisted in studying the possibility to give a proof of origin of the gold produced in mines by scientific approaches. This le us to develop the ‘geoforensic passport’. The ‘geoforensic passport’ is a tool to characterise a supplier by its chemical and isotopic composition, while using statistical methods to interpret the data. This tool refers to three levels of investigation.
The first level is based on ED-XRF chemical analyses of the doré, interpreted with geostatistical tools. This first level allows the selection of doré bars whose chemical composition does not correspond to other doré bars from the same supplier. What happens with doré that are outliers and thus have not been validated at the first level? The non-conforming doré, which can represent up to 10% of the supply of a customer undergoes further investigations. The second level involves isotopic analysis by MC-ICP-MS, which – compared to a reference database from the same supplier – allows, in many cases, to corroborate its conformity. If the sample is still not conforming, we carry out, on the third level, further investigations. This level 3 involves more sophisticated analyses of the composition of the gold by LA-ICP-MS.