We all use electronic devices like mobile phones, but where do the materials that make them come from? Tin, tungsten, tantalum and gold are the four most common 'conflict minerals', known collectively as 3TGs. Their mining causes insecurity and human rights abuses in many regions. Armed groups clash over their illegal trade. Fairphone is one manufacturer which takes responsibility to ensure its supply chains extract minerals lawfully. The European Parliament is pushing for more transparency in supply chains through mandatory OECD due diligence systems.