In actuality, the bonds have no market, let alone one backed by valuable metals. (businessinsider.com)
Still more platinum can be saved by mixing it with other, less valuable metals, such as nickel or copper. (sciencedaily.com)
The deep waters of the East Pacific hold an unprepossessing treasure trove: potato - sized lumps of rock that contain valuable metals such as manganese, cobalt and copper. (sciencenews.org)