Gold “out of the ground” typically refers to the natural state in which gold is found in ore deposits, and it is typically found in nature in its pure metallic form.  However, gold is rarely found in large, pure nuggets.  Instead, it is usually found in combination with other minerals in ore deposits.

The composition of gold ore can vary widely depending on the geological processes that formed the deposit and the surrounding rock types. Some examples of deposits that occur in various geological settings are:

Quartz Veins

Gold often forms in quartz veins that have been created by hydrothermal fluids moving through fractures in the Earth’s crust. The gold precipitates from these fluids and fills the open spaces in the quartz veins. Some quartz veins contain pockets of exceptionally pure native gold.

Placer Deposits

Placer deposits are concentrations of heavy minerals, including gold, that have been eroded from their original source rocks and transported by rivers, streams, and glaciers. Gold nuggets, flakes, and grains can accumulate in placer deposits, often in riverbeds, streambeds, or beach sands.  Placer gold can be relatively pure, especially in areas where erosion has concentrated gold particles.

Alluvial Deposits

Alluvial deposits are sedimentary deposits formed by the action of water, such as rivers, streams, and floodplains. Gold can be transported and deposited by flowing water forming alluvial deposits containing placer gold. Alluvial gold can be relatively pure, especially in areas where erosion and sedimentation processes have concentrated gold particles.

Gold ore may contain varying amounts of other elements and minerals including silver, copper, lead, zinc, iron, sulfur, and quartz, among others.  These impurities can affect the overall quality, value, and grade of the ore. To learn more about gold grades, see Gold Grade: Concentration of Gold Within an Ore Body