In a single South African gold mine, an expected $2.2bn worth of gold can still be extracted from just one dump site's waste material.
Using water cannons and chemical treatments, a single mine can hope to extract about 3 grams in every tonne. It may not sound like much, but if there is 140 million tonnes of waste lying around - the numbers start adding up.
High prices mean all the effort that goes into sourcing the precious metal may well be worth it.
Al Jazeera's Tania Page reports from Johannesburg.