Most people are familiar with the illicit trade of "blood diamonds", but few are aware of the "other" blood trade: illegally sold minerals. These minerals are crucial to the aerospace, electronics, and manufacturing industries, and their illegal sales are used to finance political militias that murder civilians in the Democratic Republic of the Congo (DRC).
Until now, there's been no way to "fingerprint" these materials to determine their origin. But now scientists may have found a way... using lasers.
Back in 2010, Congress passed the Dodd-Frank Act to prevent companies from inadvertently funding wars through the purchase of what are called "conflict minerals." The Act requires firms to verify that their products contain no cassiterite, columbite-tantalite, wolframite, or gold obtained from the DRC and its neighbors. This has proven easier said than done, because legitimate mining operations are often located near militia-controlled ones.
To help these companies distinguish "blood minerals" from those obtained in approved areas, Richard R. Hark, a chemistry professor at Juniata College, in Huntingdon, Pa., is developing a method based on laser-induced breakdown spectroscopy (LIBS). Hark's method provides a geochemical "fingerprint" for minerals, allowing firms to do a reference check and determine the source of the minerals.
According to Chemical & Engineering News, the LIBS generates the fingerprints with a laser-induced plasma that breaks down samples and excites them to emit light at specific wavelengths:
The resulting spectrum can contain thousands of spectral lines. Pattern recognition and statistical methods, typically partial least squares discriminant analysis, can tease out subtle differences between samples. The potential to do real-time analysis in the field makes this an attractive approach.
Geologically, the ores formed from solutions associated with the passage of molten rock through Earth's crust. The ores contain trace elements-especially rare-earth elements-that reflect this origin. Although any element can be excited during LIBS, the rare-earth elements account for most of the differences between signatures.
The signature of the crust is present immediately after the minerals are extracted from the earth, and it's at this stage where the fingerprinting needs to be done. After smelting, and especially when ores from different mines are mixed, identification becomes next to impossible.
To make the LIBS system more practical, therefore, Hark is working with Applied Spectra, a company based in Fremont, CA., to help in the development of a field-portable instrument. Once that's complete, they can start to develop a large database to assist in pinpointing the origins of potential conflict materials.