The BBC has a great article on the damage done from rare-earth mineral mining in mainland China. This tailings lake spews the leftover byproducts from the extraction of rare-earth minerals that are used in the production of tech gadgets. The pictures and video alone tell a interesting story.
Neodymiumum is the biggest offender, as it is used to make the super small magnets in our earbuds and smartphone speakers. The process used to extract this mineral is highly caustic and is probably the reason that China is the worlds largest exporter.