The Origin of Gold – Geoforensic Passport
In 2016, Metalor Technologies and the University of Lausanne (Switzerland) began a scientific collaboration to determine the origin of mined gold. This led to the creation of a new approach to validating the origin of doré – the geoforensic passport. This passport, which comprises a complex set of data characterising every single doré provider, was created using a multivariate statistical approach. Metalor now compares every doré received against that database, allowing it to identify any potentially problematic shipments.
OUR PROJECT LED TO THE CREATION OF THE 'GEOFORENSIC PASSPORT' A SCIENTIFIC TOOL USED TO VALIDATE THE DECLARED ORIGIN OF ANY MINED GOLD
For a very long time, the extreme complexity of the gold supply chain meant that the accurate traceability of gold was considered impossible. Associations such as LBMA, private and public organisations such as the RJC and BGI, as well as many refiners themselves have introduced responsible sourcing programmes to ensure that gold entering the supply chain is responsibly produced. However, all these initiatives have one fundamental flaw: they rely on compliance, audits and local governments in an environment that is not corruption-free.
In the past, several research projects have been undertaken to increase confidence in the gold supply chain:
- Colonel Dixon (who presented at the LBMA Assaying and Refining Conference in 2013) pioneered an approach to determining the origin of gold, which was originally used to prove the origin of gold in criminal cases. His approach was later extended to supply chain issues and is mostly based on detailed analyses of the chemical composition of gold using LA-ICP-MS.
- BGR (Bundesanstalt für Geowissenschaften und Rohstoffe) developed the analytical fingerprint methods (AFP) to monitor the supply of tin, tungsten, tantalum and gold ores in the Great Lakes region of Central Africa. Developed since 2006 to support UN initiatives in verifying the origin of conflict minerals, it comprises a reference database of all artisanal and small-scale mines in this region against which transboundary mineral shipments can be compared. This tool is based on a combination of chemical and mineralogical analyses; however, a feasibility study only has been undertaken for gold.
- BRGM (Bureau de recherches géologiques et minières) developed an approach aimed at controlling the supply of gold in Guyana and Suriname. This approach, based on the collection of doré from artisanal and small-scale mines followed by a complex mineralogical and metallographic study, turned out to be very complex, expensive and time-consuming.
This background research showed that our approach had to meet two clear objectives:
- Since gold supply involves a very large number of players around the world, and since it is impossible to collect samples from every gold mine without involving extensive field work, it was necessary to intervene at the bottleneck of the gold supply chain – the refinery.
- Any solution had to be usable for every doré received and had to be integrated at a reasonable cost into existing flows at the refinery.
Our project led to the creation of the ‘geoforensic passport’, a scientific tool used to validate the declared origin of any mined gold.
Figure 1: Multilevel analysis approach
The Geoforensic Passport
The geoforensic passport can detect irregularities in the supply of dorés upon their arrival at the refinery. It is based on a multilevel approach (see Figure 1). Level 1 relies on ED-XRF analysis followed by statistical interpretations. If a doré cannot be validated by level 1 analysis, we then move it to level 2, which introduces more sophisticated analyses, namely the determination of lead isotopic composition, and also integrates geological information. If, at this stage, there is still an inconclusive result, further investigation tools are available at level 3.
Figure 2: The geoforensic passport of a single customer (only three dimensions out of 15 are represented)