The 40 different rare metals in your phone

SCREEN: The glass is an aluminosilicate which is strengthened with potassium ions. The touch screen has indium tin oxide in the transparent film to help conduct electricity. Rare earth element compounds are needed for the colours in the screen. Others reduce ultra-violet light penetration into the phone.

ELECTRONICS: Copper is used for wiring. Gold and silver form the micro-electrical parts. Tantalum is the major component of micro-capacitors, which stabilise the power supply and generally total more than 7 0 0 . Nickel is used in the microphone. Alloys including the elements praseodymium, gadolinium and neodymium are in magnets used in the speaker and microphone. The vibration unit contains neodymium, terbium and dysprosium. Pure silicon goes into the chip. Tin and lead are employed to solder the electronics.

BATTERY: Most mobiles have lithium- ion batteries, made of lithium cobalt oxide for the positive electrode and graphite (carbon) for the negative. Some batt eri es have manganese. Casings are made from aluminium. Some cases are constructed with magnesium compounds, left. Or with plastics, some of which contain flameretardant compounds such as bromine.