Gold is one of the most precious metals on Earth and has fascinated humans for thousands of years. But how long has it actually been around? When and how was gold formed and deposited on Earth?
When Was Gold Formed?
Gold, along with other precious metals like silver and platinum, was formed billions of years ago deep within the Earth’s crust and mantle when the planet was still molten. These metals are known as “noble” metals because they are chemically unreactive and resistant to corrosion and oxidation.
The current scientific consensus is that gold formed during the late stages of the formation of the planet Earth between 4.0 to 4.6 billion years ago. As the young Earth cooled and geological activity shaped the planet’s crust, gold was carried up from the mantle to the crust in large magma or lava flows. This happened often early in the planet’s history when the interior was much hotter and more active.
Gold is an element and cannot be created or destroyed. All the gold that has ever existed – including all the gold found on Earth today – was created during these ancient processes when the planet formed and coalesced from clouds of gas and dust.
Where Does Natural Gold Come From?
Natural gold most often occurs in two types of deposits:
- Lode deposits
- Placer deposits
Lode deposits, also known as hard-rock deposits, are concentrations of gold hosted within surrounding rock. These deposits form when hydrothermal fluids transport and deposit gold into fractures, faults, and cavities in rock. Common host rocks for lode deposits include granite, quartz, and other igneous and metamorphic rock.
Placer deposits are concentrations of gold found in alluvial sands and gravels that have eroded from lode deposits. As lode deposits weather and erode over time, small fragments and particles of gold are transported downstream by rivers and streams and deposited in placer deposits such as stream beds, flood plains, and deltas.
Major Gold Deposits Around the World
Some of the largest and most significant concentrations of gold are found in the following locations:
- Witwatersrand Basin, South Africa – One of the world’s largest gold deposits, the Witwatersrand Basin represents nearly 50% of all the gold ever mined globally. This gold is hosted in conglomerate strata in the basin.
- Carlin Trend, Nevada, USA – A series of gold deposits aligned along a geological structure in Nevada. It has produced over 80 million ounces of gold and continues to be mined today.
- Homestake Mine, South Dakota, USA – One of the largest and deepest gold mines in North America. Operated between 1876 and 2001 and produced over 40 million ounces of gold.
- Cripple Creek & Victor Gold Mine, Colorado, USA – A large gold mining operation that has produced over 21 million ounces of gold since 1891. Hosted in volcanic breccias.
- Bingham Canyon Mine, Utah, USA – One of the world’s largest open pit mines that has produced significant amounts of gold along with copper and other metals.
- Muruntau mine, Uzbekistan – The world’s largest open pit gold mine by area. It has produced over 50 million ounces of gold since mining began in the 1960s.
- Grasberg mine, Indonesia – The world’s largest gold mine in terms of contained reserves. Located in the highlands of Indonesia, it also produces significant amounts of copper.
- Super Pit gold mine, Western Australia – Australia’s largest open pit mine, the Super Pit has produced over 16 million ounces of gold and continues to operate today.
- Sukari Gold Mine, Egypt – The first large-scale modern gold mine in Egypt, Sukari has produced over 4 million ounces of gold since operations began in 2009.
- Kalgoorlie Super Pit, Western Australia – A historical gold mining area, the Kalgoorlie Super Pit is Australia’s second largest open pit mine and has produced over 50 million ounces of gold.
Most major gold deposits around the world are associated with geological collision zones and areas where the earth’s tectonic plates meet. These areas provided the heat, pressure, and geological activity necessary to transport gold into economically viable concentrations.
When Did Gold First Appear on Earth?
Although gold first formed deep in the Earth between 4 to 4.6 billion years ago, it took time for natural geologic processes to concentrate it into deposits accessible to humans. The earliest evidence we have of concentrated gold deposits dates back approximately 3 to 3.5 billion years.
Some key events and time periods in the early history of gold on Earth include:
- Around 4 billion years ago – Gold is created in the Earth’s mantle during planetary formation.
- Before 3.5 billion years ago – Gold begins to be transported towards the surface and concentrated into early lode deposits as the Earth’s crust develops.
- 3.5 billion years ago – Some of the earliest evidence of gold deposits, found in areas like Barberton, South Africa and the Pilbara region in Western Australia.
- 3 billion years ago – Major geological events help concentrate gold deposits in areas like the Kaapvaal and Zimbabwe cratons of southern Africa.
- 2.5 billion years ago – Levels of atmospheric oxygen begin to rise towards modern levels, allowing formation of large gold deposits.
- 2 billion years ago – Widespread evidence of major paleoplacer deposits formed by prehistoric river systems.
So although gold formed extremely early on, it took over 1 billion years for natural geologic processes like erosion, water transport, precipitation from fluids, and plate tectonics to sufficiently concentrate it into gold deposits accessible to humans. The richest concentrations of gold largely formed between 3 to 1 billion years ago.
When Did Humans First Find Gold?
For most of geologic history, gold existed but humans did not. Humans first evolved in Africa several million years ago. The earliest known instances of humans interacting with gold occurred approximately:
- 6000 to 5000 BC – The first gold artifacts made by ancient Egyptians, like beads and small statuettes. This gold was likely retrieved from placer deposits in stream beds.
- 3500 BC – Some of the first gold mining in ancient Egypt. Gold jewelry and ritual objects from royal tombs date to this era.
- 2500 BC – Gold is used widely in jewelry and decorative objects in ancient Sumer.
- 1200 to 800 BC – Earliest evidence of gold mining in southern Africa during times of the ancient kingdom of Mapungubwe.
- 500 BC – The time of the ancient Greek and Roman empires when gold coins and artworks were common.
So although gold had existed for nearly the entire 4.6 billion year history of Earth, verifiable evidence shows humans only discovered and began utilizing gold approximately 7,000 years ago. The difficulty in accessing hard rock lode deposits confined early human use to panning for placer gold in streams.
How Rare is Gold?
Gold is a relatively rare element making up only ~0.004 parts per million of the Earth’s crust. For comparison:
- Iron makes up over 5% of the Earth’s crust.
- Aluminum makes up over 8% of the Earth’s crust.
- Gold is over 1 million times rarer than aluminum.
However, gold occurs widely enough across different continents and concentrations that the total amount of gold ever mined totals approximately 190,000 metric tons. While rare compared to other elements, known gold reserves are sufficient to meet demands into the foreseeable future.
Where is Gold Found on Earth?
While gold occurs across the world, it is concentrated in locations with a unique geological history. The geographic distribution of gold on Earth is uneven and complex.
In general, the largest concentrations of gold are found in:
- Africa – Africa has produced and exported more gold than any other continent. Large gold deposits are found across several countries in southern, west, and east Africa. The Witwatersrand basin holds over 1/3 of all the gold mined globally.
- North America – Important gold deposits are found across the United States, Canada, and Mexico. The Nevada gold trends and gold belts of Canada are especially significant.
- South America – Gold deposits and gold mining support the economies of countries like Peru, Chile, Brazil, and Argentina.
- East Asia – Major gold producing countries here include China, Russia, Indonesia, and Mongolia.
- Oceania – Australia and New Zealand have significant gold reserves and a long mining history. The Super Pit mine in Australia has produced over 50 million ounces of gold.
In general, areas located on the ancient supercontinents are more likely to have significant gold deposits. Collision zones between tectonic plates also provide ideal conditions for gold to form and concentrate.
Conclusion
In summary, gold first formed between 4 to 4.6 billion years ago during the creation of the Earth. However, it took over 1 billion additional years for natural geologic processes to sufficiently concentrate it into deposits that could be mined by humans. Although rare, natural concentrations of gold are widely enough distributed that humans have mined approximately 190,000 metric tons of gold throughout history. The presence of gold deposits across several continents means gold will likely remain an important natural resource for many years to come.