Where Is Gold Found
On Earth, gold is found in ores in rock formed from the Precambrian time onward. It most often occurs as a native metal, often in a metal solid solution with silver (i.e. as a gold silver alloy). Such alloys usually have a silver content of 8 to 10%. Electrum is elemental gold with more than 20% silver.
Native gold occurs as very small to microscopic particles embedded in rock, often together with quartz or sulfide minerals, such as pyrite – known as “Fool’s Gold”. These are called lode deposits. The metal in its native state is also found in the form of free flakes, grains or larger nuggets that have been eroded from rocks and end up in alluvial deposits called placer deposits. When ancient placer deposits mix with sediments they can form conglomerate beds. Free gold is always richer at the surface of gold-bearing veins owing to the oxidation of accompanying minerals followed by weathering, and washing of the dust into streams and rivers, where it collects and can be welded by water action to form nuggets.