Analytical Fingerprint of Wolframite Ore Concentrates

Ongoing violent conflicts in Central Africa are fueled by illegal mining and trading of tantalum, tin, and tungsten ores. The credibility of document-based traceability systems can be improved by an analytical fingerprint applied as an independent method to confirm or doubt the documented origin of ore minerals. Wolframite (Fe,Mn)WO₄ is the most important ore mineral for tungsten and is subject to artisanal mining in Central Africa. Element concentrations of wolframite grains analyzed by laser ablation-inductively coupled plasma-mass spectrometry are used to establish the analytical fingerprint. The data from ore concentrate samples are multivariate, not normal or log-normal distributed. The samples cannot be regarded as representative aliquots of a population. Based on the Kolmogorov-Smirnov distance, a measure of similarity between a sample in question and reference samples from a database is determined. A decision criterion is deduced to recognize samples which do not originate from the declared mine site.