What kind of rocks contain gold?

In nature, gold is most commonly found embedded in quartz rock veins or alluvial sand and gravel deposits after millions of years of geologic processes concentrate the rare metal. Through tectonic and volcanic activity, hot aqueous solutions leach gold from magma, transport it through faults and fractures, and precipitate the element in networks of quartz as the temperature drops. This leaves gold entrapped in quartz rock formations hundreds of meters underground.

Erosion later releases gold from disintegrating quartz veins into rivers where it amalgamates with sedimentary grains in alluvial deposits along rivers and floodplains. These sands and gravels contain accumulated gold and quartz pebbles eroded from gold-bearing veins. Fine flakes and dust can be recovered via gravity separation.

Trace amounts of gold also occur in pyrite, galena, chalcopyrite, mispickel, calaverite, sylvanite, and krennerite iron-sulfide ores. These are less common host rocks but are occasionally mined when gold prices are high enough to justify extraction.

Finding quartz with visible gold inside remains the quintessential indicator of gold presence for prospectors. While gold has an affinity for quartz, not all quartz veins bear gold. Other geological factors like structural controls near shear zone intersections increase likelihood of gold deposition.

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