Rebels from the Revolutionary Armed Forces of Colombia (FARC), enter a small town near Miranda, Colombia, Wednesday, April 17, 1996. A column of the same rebel group ambushed a military convoy Monday killing 31 soldiers and wounding 18 outside the town of Puerres, located 350 miles southwest of Bogota. The FARC are the largest and oldest guerrilla group in Colombia. (AP Photo/Ricardo Mazalan)

Bloomberg Markets is reporting that BMW, Volkswagen and Ferrari have been using tungsten ore sourced from Colombia's FARC rebel terrorists. The extensive story focuses on Colombia's illegal mining trade and calls into question the provenance of the rare ore that is used not only in crankshaft parts production, but is also found in the world's computing and telecommunications industry for use in screens.

The ore is mined by the FARC (Fuerzas Armadas Revolucionarias de Colombia, or Revolutionary Armed Forces of Colombia – People's Army), and exported to Pennsylvania, where it is refined. The refined ore is then sent over to Austria, where a company called Plansee turns it into a finished product. Now, it's important to note that we aren't talking about the world's supply of tungsten here. In 2012, Plansee's American refinery purchased 93.2 metric tons of tungsten, valued at $1.8 million. That's peanuts, with the entire Colombian tungsten mining industry producing just one percent of the world's supplies.

That doesn't make indirectly supporting FARC any more acceptable, though. BMW, VW and Ferrari are all committed to not accepting mineral supplies from the Democratic Republic of Congo, which is also in the grips of a guerrilla insurrection funded, in part, by illegal mining. The same commitment would figure to extend to Colombian mining, but as BMW points out, it's difficult for a multi-national manufacturer to know where every item in its supply chain comes from. A company spokesperson says as much, telling Bloomberg, "These few grams out of the billions of tons of raw materials passing through the BMW supply chain are of no practical relevance."

This response is perhaps somewhat blasé, but BMW, Ferrari and Volkswagen aren't directly negotiating with the FARC rebels, and we'd be stunned if the three manufacturers were even aware of where the tungsten was coming from. By the time it arrives in their respective factories, it's traveled from Colombia, to Pennsylvania to Austria, making for a rather difficult web of countries and networks to track. Even so, with Bloomberg drawing a spotlight on the activities, we're assuming a few phone calls are going to be made.