LIBS may trace origins of “conflict” minerals

Raleigh, NC and Huntingdon, PA--Scientists at the Army Research Laboratory and Juniata College are adapting laser-induced breakdown spectroscopy (LIBS) for ore-sample fingerprinting of minerals mined in war-torn regions.

While the metal tantalum is valuable for use in laptops, mobile phones, and other electronics, it has also been blamed for fueling the ongoing war in Congo, and is thus termed a "conflict" mineral when mined from that region. Armed groups involved in the conflict often control the mines for metals such as tantalum, tin, tungsten, and gold and tax the trading routes along which the materials pass. Electronics companies, governments, and human-rights organizations have been developing methods to prevent the sale of these conflict minerals.

Scientists at Germany's Federal Institute of Geosciences and Natural Resources (Hannover, Germany) began working in 2007 on a two-stage method to find the chemical fingerprint of a piece of tantalum ore and discern its origin. The first stage used custom software and an electron microscope to analyze and identify 10,000 to 20,000 mineral grains of the product derived from a tantalum mine, called an ore concentrate. The second uses a type of laser analysis to zoom in on 50 of those grains, analyze major and minor components, as well as the isotopes, to provide more detail about the age of the sample. The technique can often pinpoint the origin of an ore to a limited area within a given country, and sometimes to a specific deposit. The technique also requires two expensive laboratory instruments and two to three days to do the tests. No lab in Congo is currently sophisticated enough to perform these tests.

Even if a test could say that a shipment of ore came from within 100 miles of a given point in Congo, that still might not be good enough, said Sasha Lezhnev, a consultant to the Enough Project, an organization that works in Africa to end genocide and crimes against humanity. He stressed that the volatility of control of a given area or mine increases the need to resolve the origin down to a small area. "If you can pinpoint it to a 10 mile radius or a 5 mile radius or something like that, then that's actually helpful," he said.

LIBS: instantaneous analysis
American researchers are working to adapt a different, faster technique for ore-sample fingerprinting: LIBS. A laser is focused onto a sample's surface, heating and breaking down a small portion into plasma; the resulting spectral lines reveal the chemical profile of the material.

"It's the only system that is field portable, gives you real time answers, and can analyze all elements," said Russell Harmon, a geochemist at the Army Research Office of the Army Research Laboratory. "You can instantaneously acquire that information and know right away what's in the sample that you're looking at." He noted that the laser-induced technique could screen ore shipments before they are refined.

Currently, Harmon and his colleagues at Juniata College have accumulated and analyzed a small fraction of the samples that they need to develop a comprehensive profiling tool. More trials will be needed, as well as access to additional samples.

If the technique proves to be successful, it could provide an valuable tool for companies trying to abide by a provision attached to the July 2010 U.S. financial regulation bill, which called for the Securities and Exchange Commission to establish standards for companies to follow in disclosing the steps they take to avoid purchasing conflict materials.

Source: http://www.insidescience.org/policy/tracking-conflict-minerals-in-congo