noun
urban mine
Refers to discarded electronic devices and other urban waste that contain valuable metals and can be recycled as resources.
使用済みの携帯電話は都市鉱山と呼ばれる資源の宝庫だ。
Used mobile phones are a treasure trove of resources called urban mines.
リサイクル is the general process of recycling, while 都市鉱山 specifically refers to the accumulated waste itself as a source of materials.
Compound of 都市 (city) and 鉱山 (mine), literally 'city mine'. A relatively modern term reflecting the concept of recovering resources from urban waste.