In nature, gold most often occurs in metallic form, alloyed with silver. However, it can also be found as a pure element, chemically combined with tellurium or alloyed with other metals such as mercury and copper.
Gold is usually found in rocks, quartz veins and alluvial deposits. However, commercial gold is mined from either lode deposits or placer deposits. Lode deposits are concentrations of gold particles embedded in rock, whereas placer deposits are loose grains of gold that have eroded from rocks and accumulated in sediments on stream beds or beaches. Gold mining is carried out through underground drilling, open-pit or panning techniques, depending on the type and location of the deposit.