Gold mining
Gold mining is the extraction of gold from ore and sediments through methods such as placer washing, underground mining, and open-pit mining.
Gold deposit: A natural concentration of gold in rock or sediment that can potentially be extracted. Deposit type and concentration determine which mining method can recover gold economically.
Gold: A dense, malleable chemical element with symbol Au and atomic number 79. Its chemical stability and density shape how miners locate, separate, and process it.
Gold processing: The crushing, concentration, and chemical treatment of ore to recover its valuable minerals. Processing turns extracted gold-bearing rock into material from which gold can be recovered.
Acid mine drainage: Acidic, metal-rich water produced when exposed sulfide minerals react with air and water. Excavated and waste rock can generate polluted drainage long after mining ends.
Dredging: The removal of sediment from the bottom of a body of water or waterway. Dredges recover submerged placer deposits, unlike surface washing or hard-rock extraction.
Placer mining: Mining that recovers valuable minerals from loose sediments using their differences in density. It separates gold grains from stream or ancient river sediments by washing.
Ore: Rock or sediment containing valuable material in a concentration that can be mined economically. Gold mining targets material whose gold content justifies the costs of extraction.
Heap leaching: A process that irrigates a prepared heap of ore with a solution that dissolves target metals. Some low-grade gold ores are treated in heaps rather than conventional processing plants.
Mercury pollution: Environmental contamination caused by mercury released into air, water, or soil. Artisanal gold processing may use mercury, which can expose people and ecosystems to toxic contamination.
Mountaintop removal mining: A form of surface coal mining that removes a mountain summit to reach underlying seams. Its coal-specific landscape-scale excavation contrasts with the usual methods used for gold.