From VOA Learning English, this is the Economics Report.

Researchers have produced a new map of mining areas in the Democratic Republic of Congo. The map shows mines under the control of the Congolese army and armed groups. The study suggests that the top conflict mineral in the area is now gold.

A Belgian group, the International Peace Information Service (IPIS), carried out the study in partnership with the DRC registry of mines. The researchers found that armed groups were involved in about 200 of the 800 mines they studied, the Congolese army was involved at 265 mines. The researchers reported that both the military and the militias are taxing mine workers illegally.

The International Peace Information Service carried out a similar survey in 2009. Filip Hilgert was the lead researcher. He told VOA the map they made 4 years ago is no longer correct. He said many of the miners are now digging for gold, and he said the armed groups are profiting much more from gold than from other conflict minerals, such as tin, tungsten and tantalum. These minerals are often called the "three T's."

One reason for the change has been an increase in the price of gold. Another reason has been stronger international rules for mineral imports. The United States Congress passed legislation to fight the trade of conflict minerals. Mr Hilgert says such efforts have had a big effect on trade in the three T's, but it has not affected the gold trade.

Judith Sargentini is a member of the European Parliament. She has been campaigning for a European law on conflict minerals. She notes that gold like diamonds is easy to transport in small amounts, that explains why it is hard to know where it was mined.

The German geological institute BGR (Bundesanstalt für Geowissenschaften und Rohstoffe) has collected minerals from hundreds of mines in Rwanda. The collection could be used to prove whether a sample of minerals came from a conflict area. But Judith Sargentini suggests that geophysical tests will not work. She says buyers need to know about their suppliers.

"You cannot solve every trade in a commodity by trying to find out what the geological background of a material is. It shows that you need, first of all, a due diligence supply chain, and second of all, initiatives that lead to fairtrade gold mining," said Sargentini.

Due diligence in this case means knowing and being able to trust your supplier.

And that is the Economics Report for VOA Learning English. I'm Mario Ritter.