There is far more aluminium — which is used to make your phone's outer case — than any other metal, however.
Aluminium comprises around 24% of an iPhone's mass, followed by iron, which makes up around 14% of the device's mass, according to a breakdown from Motherboard. Copper and cobalt comprise around 6% and 5% of the phone's mass.
Aluminium is one of the most abundant metals in the Earth's crust, though it doesn't exist in a pure state in nature. Instead, it's produced by refining bauxite ore. Canada is the largest exporter of aluminium to the US, while China is the world's biggest aluminium producer.
Rare Earth elements like yttrium and europium are crucial to your iPhone's function — they're used in the phone's battery, as well as to help give the display screen colour and make the phone vibrate when you get a text, among other uses. Although they account for only a fraction of a percent of the phone's total mass, these elements have made mining rare earth elements a huge business.
Japanese scientists recently found an underwater, "semi-infinite" deposit of these elements, including valuable yttrium, off of Minamitori Island, about 1,800km southeast of Tokyo.
Expert's say Japan's cache could help revitalise the country's flagging economy and put a dent in China's trade monopoly.
Booming demand for these elements also has an environmental cost. The ore, or rocks, from which these elements are obtained are laced with radioactive materials and carcinogens that can leak into the water supply and destroy forests and farmland surrounding the mines, reports The Guardian.
Miners can also suffer severe health effects, including cancer and other diseases.
Last year, however, Apple said it would seek to stop using mined rare earth elements to make phones, and instead use only recycled materials, Quartz reported.
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