Geochemical Fingerprinting of Conflict Minerals Using Handheld XRF: An Example for Coltan, Cassiterite, and Wolframite Ores from Democratic Republic of the Congo, Africa

Alireza K Somarin

doi:10.3390/min9090564

Abstract

Conflict minerals are those mined in politically unstable regions of the world and are then sold to finance war or other illegal activities. Industrial manufacturers are required to show that minerals used in their applications are not derived from conflict areas. Several geochemical and geochronological methods have been suggested to fingerprint conflict minerals; however, all these methods require sophisticated and extensive laboratory procedures. Portable X-ray fluorescence data of 108 samples from various location in Democratic Republic of the Congo shows that cassiterite and wolframite ores from all studied regions can be fingerprinted using various discrimination diagrams. Coltan ore samples from several regions can also be discriminated using major and trace elements of these samples. In addition, patterns in chondrite-normalized spider diagrams for each region are unique and can be used as fingerprinting tools.

Highlights

Conflict minerals have always been an attractive topic, from a scientific point of view and from political, international, and industrial views; these minerals can be used to fund war or illegal activities
This paper examines the use of HHXRF in delineating geochemical features of columbite, tantalite, cassiterite and wolframite ores from various regions of DRC
Visual examination of cassiterite ore specimens indicates that some regions have darker color samples

Summary

Introduction

Conflict minerals have always been an attractive topic, from a scientific point of view and from political, international, and industrial views; these minerals can be used to fund war or illegal activities. The built-in TaHf calibration program was determined to be the most suitable method as it provides simultaneous analysis of suite of elements (Table 3), including the vital elements for discrimination purposes This is a factory built-in special mode designed for coltan and associated minerals; in this mode, the performance of the analyzer is enhanced by eliminating elements with X-ray energies close to Nb and Ta. The energy values (in kilo electron volt, Kev) for Kα, Kβ, Lα, and Lβ lines are respectively 16.61, 18.62, 2.17, 2.26 for Nb and 57.52, 65.21, 8.15, 9.34 for Ta. Factory calibration can produce reliable data for some elements ( base metals) in some rock/soil matrices; the analytical accuracy and precision can be low mainly due to peak overlap or matrix difference between the analyzed unknown sample and factory calibration samples.

Results

Discussion

Fingerprinting

Conclusions