Gold comes from almost every continent, with China and Australia the largest producers as of 2015, according to Mining Technology. A team of Harvard scientists believes that gold is formed when two neutron stars collide, according to a report by USA Today.
The United States is the third largest producer of gold, according to Mining Technology. Russia, Peru, Ghana and Uzbekistan are also among the top gold producers. Three U.S. mines were on the list of the 10 most prolific mines in 2011, although the Witwatersrand Basin in South Africa tops that list, reports CMI Gold and Silver.
Part of the reason gold is so widely found on Earth may be due to its extraterrestrial origins. Gold was present when the Earth was formed, but the original gold sank down into the Earth's core as the planet stabilized, claims BBC News. Scientists are not sure how gold became so common in the Earth's mantle, but research shows meteorites might be responsible, reports Science Daily. This theory claims that a massive meteor bombardment approximately 4 billion years ago brought gold to the upper layers of the Earth.
Some scientists disagree with this theory and think that most gold was already on Earth when the planet formed, according to BBC News. Instead of being pulled down into the Earth's core, it remained in an ocean of magma just below the mantle. Volcanic eruptions then brought it into the mantle.