https://www.mdpi.com/2071-1050/16/6/2509 https://www.mdpi.com/2071-1050/16/6/2509 "Indeed, a natural ore mine can produce 5 g of gold (Au) per ton of ore, whil

https://www.mdpi.com/2071-1050/16/6/2509 https://www.mdpi.com/2071-1050/16/6/2509 "Indeed, a natural ore mine can produce 5 g of gold (Au) per ton of ore, while 200–250 g Au can be recovered from the same mass of computer boards (300–350 g Au/t for mobile phones) [6]."