Gold supply is regularly criticised for social and environmental damage at mine sites and along the supply chain or for the lack of transparency in transactions. Switzerland plays a leading role in the global gold market: between 60-70% of gold is refined here. One of the major challenges is that the origin of gold is not always known with certainty: even though responsible sourcing programmes for precious metals have often been developed over the last decade, emanating from associations such as the LBMA (London Bullion Market Association), private and public organisations (RJC – Responsible Jewellery Council, BGI – Better Gold Initiative…) as well as many refiners themselves, these initiatives have a fundamental flaw: they rely on compliance, audits and local governments that are often not corruption-free, to the point of becoming a risk to Switzerland’s reputation. Our project provides an innovative solution through scientific approaches to this societal and market demand for greater transparency in the gold trade.
Our approach aims at confirming the origin of the doré bars by physico-chemical analyses, which therefore provide scientific proof, making fraud difficult. Our study focuses on the production of gold coming mainly from industrial mines and on the issues at the interface between industrial and artisanal mines. The feasibility of this confirmation of origin was the subject of an Innosuisse project. It is based on the determination of a geoforensic gold passport from a supplier and is carried out in three levels:
Level 1: On arrival at the refiner, Metalor Technologies in this case, the doré bars (i.e. gold ingots pre-refined at the mine or in its immediate vicinity) are subjected to chemical screening to assess the content of twenty chemical elements. This screening, which is therefore already integrated into the refiner’s process and which aims to check for the presence of deleterious and potentially dangerous elements, is then used for statistical evaluation with a view to determining gold with a non-compliant chemical composition. This non-conformity therefore highlights samples with a different chemical composition compared to other doré bars from the same supplier. This is the case for approximately 10% of the doré bars (this varies depending on the country and the original supplier). Sampling is then necessary for further investigation, see level 2.
Level 2: The doré bars declared non-compliant after the chemical screening of the first level are subjected to isotopic analysis. The isotope ratios of lead, for example, are not changed during metallurgical processes. These isotopic ratios therefore enable to make a direct link between an ore deposit and gold from this deposit, but must also be the same for all doré bars of a specific supplier. The isotopic signature of a doré bar which does not correspond to the signature of other doré bars from the same supplier must therefore be considered as non-compliant, the sample thus selected (approximately 50% of the doré bars from this level) goes to level 3.
Level 3: A non-conformity detected during the two previous levels can have several reasons: false declarations, mixing of several sources, voluntary or involuntary contamination during the pre-refining process, anomaly of the ore deposit, etc. A detailed analysis of the chemical composition can determine the source and thus select, with scientific reliability, the doré bars that should be considered illicit. This level is currently the subject of a preliminary study.
Although the results of our approach provide certainty about the technical feasibility of scientific traceability, they also raise questions that require specialist input:
– At the technical level: how to improve the selection process of a non-compliant doré bar in the first stage? It is therefore a question of automation, detailed in sub-project 1.
– At the scientific level: Can we better foresee the reasons, the sources of this declaration of non-conformity of doré bar? Indeed, the reasons listed are currently based on blind tests, which aimed at voluntarily inserting falsified samples in a test series. Details of this approach can be found in sub-projects 2, 3 and 4.
– And finally, in an area that suffers from a lack of transparency, it is important for us to show maximum transparency, which is detailed in sub-project 5.